INFRARED LUMINOSITIES AND AROMATIC FEATURES IN THE 24 μm FLUX-LIMITED SAMPLE OF 5MUSES

Yanling Wu; George Helou; Lee Armus; Diane Cormier; Yong Shi; Daniel Dale; Kalliopi Dasyra; J. D. Smith; Casey Papovich; Bruce Draine; Nurur Rahman; Sabrina Stierwalt; Dario Fadda; G. Lagache; Edward L. Wright

doi:10.1088/0004-637X/723/1/895

1. INTRODUCTION

Infrared bright galaxies play critical roles in galaxy formation and evolution. The InfraRed Astronomical Satellite (IRAS) facilitated the study of an important group of objects, the Ultra-Luminous InfraRed Galaxies (ULIRGs; Soifer et al. 1989; Sanders & Mirabel 1996), which were first hinted at by ground observations of Rieke & Low (1972). Studies from the Infrared Space Observatory (ISO; Elbaz et al. 1999) and the Spitzer Space Telescope (Houck et al. 2005; Yan et al. 2007) later revealed that LIRGs and ULIRGs are much more common at high redshift than in the local universe. The number density of IR luminous galaxies evolves strongly with redshift to at least z ∼ 1 (Le Floc'h et al. 2005). The fraction of galaxies powered by star formation versus active galactic nucleus (AGN) is still controversial, but is crucial for determining unbiased luminosity functions for various categories of objects and understanding the evolution process.

The superb sensitivity of the Spitzer Space Telescope (Werner et al. 2004) has led to the discovery of new populations of faint, high-redshift galaxies with extreme IR/optical colors (Dickinson et al. 2004; Houck et al. 2005; Weedman et al. 2006; Yan et al. 2007; Caputi et al. 2007; Dey et al. 2008; Dasyra et al. 2009; Murphy et al. 2009). However, these studies often have at least one other constraint than the mid-IR flux limit, usually a minimum R-band magnitude or an IRAC-based color selection, designed to favor sources in specific redshift ranges, or with high luminosity. The 5 Millijanksy Unbiased Spitzer Extragalactic Survey (5MUSES) is an infrared selected sample. A major advantage of 5MUSES is its simple selection: $f_\nu (24 \rm \;\mu m)>5$ mJy. This relatively bright flux limit allows for a more detailed study of the infrared properties, filling in the gap between local galaxies and high redshift samples, and helping to improve the modeling of galaxy populations and their evolution.

In order to advance our understanding of the properties and evolution of galaxies, it is crucial to obtain accurate estimates of their bolometric luminosities. Several studies have shown that monochromatic luminosities in the mid-IR can be used to estimate L_IR (Sajina et al. 2007; Bavouzet et al. 2008; Rieke et al. 2009; Calzetti et al. 2010), and the uncertainties on these estimates decrease significantly when far-infrared (FIR) fluxes are available (Kartaltepe et al. 2010). However, the spectral energy distribution (SED) of star-forming galaxies, AGNs and ULIRGs display a wide range of shapes (Weedman et al. 2005; Brandl et al. 2006; Smith et al. 2007; Armus et al. 2007; Hao et al. 2007; Wu et al. 2009; Veilleux et al. 2009). Applying these methods without knowing a source's spectral type could cause significant biases in luminosity estimates between types of objects and seriously mislead the interpretations. The 5–36 μm spectra obtained by the Infrared Spectrograph (IRS; Houck et al. 2004) for the 5MUSES sample allows for aromatic feature identification, excitation line analysis, and decomposition into star formation and AGN components, thus providing essential information for classifying the origin of the luminosity.

The mid-IR is home to a set of broad emission line features, which are thought to originate from Polycyclic Aromatic Hydrocarbons (PAHs; Puget et al. 1985; Allamandola et al. 1989). PAHs are organic molecules that are ubiquitous in our own Galaxy (Peeters et al. 2002) and nearby star-forming galaxies (Helou et al. 2001; Smith et al. 2007). In total, they can contribute a significant fraction (10% or more) of the total infrared luminosity in star-forming galaxies. PAHs are weak in low-metallicity galaxies (Madden et al. 2006; Wu et al. 2006; Engelbracht et al. 2008), or in galaxies with powerful (Roche et al. 1991; Weedman et al. 2005; Armus et al. 2007; Desai et al. 2007; Wu et al. 2009) or even weak AGNs (Smith et al. 2007; Dale et al. 2009). The PAH features, including their profiles, central wavelengths, and band-to-band intensity ratios, have been studied in detail by Peeters et al. (2002), Smith et al. (2007), and most recently reviewed by Tielens (2008). The 6.2 μm feature and the 7.7 μm complex are attributed to vibrational modes of the carbon skeleton. The 8.6 μm feature is attributed to in-plane C–H bending, while the features at 11.3 μm and 12.7 μm are identified as out-of-plane C–H bending modes. It is generally thought that charged PAHs radiate more strongly in the C–C vibrational modes, while neutral PAHs radiate strongly in the out-of-plane C–H bending modes at 11.3 μm and 12.7 μm. The fraction of the power radiated by PAH in the different bands following single-photon heating depends on both the PAH ionization and on the size of the PAH (Draine & Li 2007). Thus, the observed variations in the PAH band-to-band ratios can reflect variations in physical conditions (Smith et al. 2007; Galliano et al. 2008; Gordon et al. 2008; O'Dowd et al. 2009).

Because PAH emission can be very prominent in star-forming systems, it has often been used as a relatively extinction-free diagnostic tool to constrain star formation. Detailed studies on the properties of PAH features locally (Spoon et al. 2007; Desai et al. 2007) and at higher redshift (Yan et al. 2005; Houck et al. 2005; Huang et al. 2009) reveal differences in the PAH equivalent widths (EWs) and L_PAH/L_IR ratios. This might indicate that some evolution in the PAH properties occurs with redshift, or that sample selection effects make for large variations in the aromatic feature properties. However, one cannot simply apply our knowledge from the local universe to high redshift galaxies, or make fair comparisons between the two unless truly equivalent samples have been studied. Current analysis on the PAH properties are based on ISO or Spitzer observations of relatively bright objects, which have been selected because of previously known optical or IRAS criteria. Thus, it is crucial to have a complete or at least unbiased census of galaxies in order to understand the galaxy evolution process and its relation to the aromatic feature emission.

In this paper, we study the properties of PAH emission and IR luminosities. This is the first of a series of papers to study the IR selected representative sample of 5MUSES. G. Helou et al. (2010, in preparation) will address the general properties of the sample and how it bridges the gap between local and high-z galaxies. Y. Shi et al. (2010, in preparation) will present the correlations between old stars and current star formation. Detailed population modeling will also be performed to address the bimodal distribution of the PAH EWs discovered in this study. In Section 2, we briefly describe the sample selection, data reduction, and measurements of spectral features. We introduce our library of empirical IR SED templates built upon Spitzer observations in Section 3,and derive the total infrared luminosities for 5MUSES galaxies. We also discuss how well one can constrain the IR SED if only mid-IR data are available. In Section 4, we study the properties of PAH emission from our flux-limited sample. Finally, we present our conclusions in Section 5. Using the IR luminosities we derived in Section 3 and the PAH luminosities from Section 4, we discuss estimation of L_IR from PAH luminosity or monochromatic continuum luminosity in the Appendix. Throughout this work, we assume a ΛCDM cosmology with H₀ = 70 km s⁻¹ Mpc⁻¹, Ω_m = 0.27 and Ω_λ = 0.73.

2. OBSERVATIONS AND DATA ANALYSIS

2.1. The Sample

5MUSES is a mid-IR spectroscopic survey of a 24 μm flux-limited ( $f_{24\rm \;\mu m}>5$ mJy) representative sample of 330 galaxies. The galaxies are selected from the SWIRE fields (Lonsdale et al. 2003), including Elais-N1 (9.5 deg²), Elais-N2 (5.3 deg²), Lockman Hole (11.6 deg²), and XMM (9.2 deg²), in addition to the Spitzer Extragalactic First Look Survey (XFLS; 5.0 deg²) field (Fadda et al. 2006). It provides a representative sample at intermediate redshift (〈z〉 ∼ 0.144) which bridges the gap between the bright, nearby star-forming galaxies (Kennicutt et al. 2003; Smith et al. 2007; Dale et al. 2009), local ULIRGs (Armus et al. 2007; Desai et al. 2007; Veilleux et al. 2009), and the much fainter and more distant sources pursued in most z ∼ 2 IRS follow-up work to date (Houck et al. 2005; Yan et al. 2007). The full details of the sample, including selection criteria and observation strategy are covered in G. Helou et al. (2010, in preparation).

2.2. Observation and Data Reduction

Because of its selection in the SWIRE and XFLS fields, IRAC 3.6–8.0 μm photometry is available for the entire 5MUSES sample. In addition to the Multiband Imaging Photometer for Spitzer (MIPS; Rieke et al. 2004) 24 μm photometry used to select this sample, 90% of our sources have also been detected at 70 μm and 54% have been detected at 160 μm. Low-resolution spectra (R = 64–128) of all 330 galaxies in 5MUSES have been obtained with the short–low (SL: 5.5–14.5 μm and long–low (LL: 14–35 μm) modules of the IRS using the staring mode observations. The integration time on each object was estimated based on its 24 μm flux densities and typically ranges from 300 to 960 s (see Table 1). A subset of the 5MUSES sample has also been observed with the high-resolution modules of the IRS, which will be covered in a future paper.

Table 1. On-source Integration Time of the Sample

f_24 μm (mJy)	SL2 (s)	SL1 (s)	LL2 (s)	LL1 (s)
5–7	480	480	480	480
7–10	480	240	240	240
10–15	480	480	180	180
15–25	240	120	120	120
>25	120	120	60	60

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The low-resolution IRS data were processed by the Spitzer Science Center data reduction pipeline version S17. The two-dimensional image data were converted to slopes after linearization correction, subtraction of darks, cosmic-ray removal, stray light, and flat-field correction. The post-pipeline reduction of the spectral data started from the pipeline products basic calibrated data files. We took the median of all images from the off-source part of the slit (off-order and off-nod) and then subtracted it from the image on the source. Then, we combined all the background-subtracted images at one nod position and took the mean. The resulting images were then cleaned with the IRSCLEAN package¹³ to remove bad pixels and apply rogue pixel correction.

We used the Spitzer IRS Custom Extractor (SPICE)¹⁴ software to extract the spectra. With a flux limit of 5 mJy at 24 μm, we chose to use the optimal extraction with point-source calibration because it significantly improved the signal-to-noise ratios (S/Ns) for our sources. When using the optimal method, each pixel was weighted by its position, based on the spatial profile of a bright calibration star. The outputs from SPICE produced one spectrum per order at each nod position, which were then combined. We also trimmed the ends of each order where the noise rose quickly. Finally, the flux-calibrated spectra of each order (including the first, second, and third orders) and module were merged without applying any scaling factor between SL and LL, and yielded a single spectrum per source. This spectrum was used to estimate aromatic feature fluxes, continuum flux densities at various wavelengths and line fluxes.

2.3. Data Analysis

2.3.1. The PAH Fluxes and Equivalent Widths

To study the properties of PAH emission in our sample, we have used two methods to estimate the feature strength. The first method defines a local continuum or "plateau" under the emission features at 6.2 and 11.3 μm by fitting a spline function to selected points, and measures the features above the continuum. The wavelength limits for the integration of the features are approximately 5.95–6.55 μm for the 6.2 μm PAH and 10.80–11.80 μm for the 11.3 μm PAH. We have not taken into account the possibility of water ice or hydroaromatic carbon (HAC) absorption in our measurement of the 6.2 μm PAH EW because these features are known to be important mainly in strongly obscured local ULIRGs (Spoon et al. 2004); thus, neglecting this component does not significantly change the 6.2 μm PAH EW. Although the 9.7 μm silicate feature could affect the measurement on the 11.3 μm PAH, our sample has very few deeply obscured sources. The PAH EWs are derived by dividing the integrated flux over the average continuum flux in each feature range. This PAH EW measured from the spline fitting method is defined as the "apparent PAH EW" and is directly comparable to the studies in the literature such as Peeters et al. (2002), Spoon et al. (2007), Armus et al. (2007), Desai et al. (2007), Pope et al. (2008), and Dale et al. (2009). In the second method, we use the PAHFIT software (Smith et al. 2007) to measure the PAHs in our sample (see Figure 1 for examples). In PAHFIT, the PAH features are fit with Drude profiles, which have extended wings that account for a significant fraction of the underlying plateau (Smith et al. 2007). As has been shown in Smith et al. (2007) and Galliano et al. (2008), although the PAHFIT method gives higher values of PAH integrated fluxes or EWs due to the lower continuum adopted than the "apparent PAH EW" method, the two methods yield consistent results on trends, such as the variations of band-to-band PAH luminosity ratios. Throughout this paper, when we refer to PAH EWs, we mean the apparent PAH EWs measured from the spline fitting method and they are used to classify object types. When we refer to PAH flux or luminosity, we mean the values derived from PAHFIT.

**Figure 1.** Examples of PAHFIT decomposition of 5MUSES spectra (black squares) with strong, moderate, weak PAH emission and with silicate absorption. The best-fit SED (green) is composed of thermal dust continua (red), PAH features (blue), stellar light (magenta), and emission lines (purple).
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2.3.2. The Fine-structure Line Fluxes

The mid-IR has a rich suite of fine-structure lines. [S iv]10.51 μm, [Ne ii]12.81 μm, [Ne iii]15.55 μm, [S iii] 18.71/33.48 μm, and [Si ii]34.82 μm are the most frequently detected fine-structure lines in the spectral range covered by the IRS. The high-excitation line of [O iv]25.89 μm has often been detected in low-metallicity galaxies, starburst galaxies or AGNs, excited by the shocks associated with intense star formation or nuclear activity, while the [Ne v]14.32/24.32 μm lines are frequently detected in AGN-dominated sources and serve as unambiguous indicators of an AGN.

We use the ISAP package in SMART (Higdon et al. 2004) to measure the strength of the fine-structure lines. A Gaussian profile is adopted to fit the lines above a local continuum. The continuum is derived by linear fitting except for the [Ne ii]12.81 μm line, which is blended with the 12.7 μm PAH feature. The continuum underlying the [Ne ii] line is fit with a second-order polynomial. The integrated fitted flux above the continuum is taken as the total flux of the line. Upper limits are derived by measuring the flux with a height of three times the local rms and a width equal to the instrument resolution. In this paper, we only use the flux ratio of [Ne iii]/[Ne ii] to compare with the PAH strength, while the tabulated line fluxes will be presented and discussed in a future paper.

3. THE INFRARED LUMINOSITIES OF THE 5MUSES SAMPLE

Several SED libraries have been built to capture the variation in the shape of IR SEDs and to estimate L_IR (Dale & Helou 2002; Chary & Elbaz 2001; Draine & Li 2007; Rieke et al. 2009). In the absence of multi-wavelength data, monochromatic luminosities have also been widely used to estimate L_IR (Sajina et al. 2007; Bavouzet et al. 2008; Rieke et al. 2009; Kartaltepe et al. 2010). The 5MUSES sample has mid-IR spectra, in addition to the IRAC and MIPS photometry, which allows us to account properly for variations in the SED shape and obtain more accurate estimates of L_IR.

3.1. Constructing an SED Template Library

In order to cover a wide range of SED shapes to fit the 5MUSES sources, we have built an IR template library based on the recent observations obtained from Spitzer. The library encompasses 83 ULIRGs observed by the IRS Guaranteed Observation (GTO) sample (Armus et al. 2007); 75 normal star-forming galaxies from Spitzer Infrared Nearby Galaxies Survey (SINGS; Kennicutt et al. (2003)); and 136 Palomar-Green (PG) and 2MASS quasars (Shi et al. 2007). The templates in the library consist of SEDs derived from IRS spectra and/or IRAC and MIPS photometry. For both the ULIRG and PG/2MASS sources, full 1–1000 μm SEDs have been obtained by J. A. Marshall et al. (2010, in preparation) and Y. Shi et al. (2010, in preparation) from IRS, MIPS, and IRAS observations. For the SINGS galaxies, Dale et al. (2007) have provided SED fits to the MIPS 24, 70, and 160 μm photometry using the Dale & Helou (2002) templates. However, these templates do not sample the full variation of the strength of PAH features in the 5–15 μm regime, due to the limited mid-IR spectra available when the templates were created. As a result, when we use SINGS galaxies as templates, we use their FIR SED from the fits of Dale et al. (2007), while in the mid-IR, we use the observed IRAC photometry integrated from the whole galaxy. This extensive template library provides a good coverage on the variations of IR SEDs. 33% of our sources are best-fit with SINGS-type templates and 38% are best-fit with quasar-type templates. The remaining sources are best-fit by ULIRG-type templates. The type of the best-fit template also correlates well with the 6.2 μm PAH EWs. Starburst (SB)-dominated sources are normally best fit by SINGS-type templates and AGN-dominated sources are best-fit with quasar-type templates. For SB-AGN composite sources, the best-fit templates are divided among ULIRG, SINGS, and quasar-type templates (48%, 37%, and 15%, respectively).

3.2. Estimating L_IR Using Spitzer Data

Out of the 330 sources in 5MUSES, 280 galaxies have redshifts from optical or mid-IR spectroscopy. We are in the process of obtaining spec-z for the remaining 50 sources. We have estimated redshifts for 11 out of these 50 objects from silicate features or very weak PAH features, but do not include them in the discussion of this paper because of the large associated uncertainties. For the 280 objects, we use a combination of synthetic IRAC photometry obtained from the rest-frame IRS spectra, as well as the observed MIPS photometry to compare with the corresponding synthetic photometry from the SED templates and estimate total L_IR. We select the best-fit template by minimizing χ² and we use progressively more detailed and accurate L_IR estimation methods for 5MUSES source with more photometry available. The final SED is composed of the IRS spectrum in the mid-IR and the best-fit template SED in the FIR. In the remainder of this section, we describe our method for estimating L_IR and the associated uncertainties.

3.2.1. Sources with MIPS FIR Photometry

For sources with FIR detection at MIPS 70 and 160 μm, we use five data points to fit their SEDs. The first two data points are rest-frame IRAC 5.8 and 8.0 μm¹⁵ derived by convolving the rest-frame 5MUSES spectrum with the filter response curves of IRAC 5.8 and 8.0 μm. The other three data points are the observed MIPS 24, 70, and 160 μm photometry for each 5MUSES source. The corresponding data points from the templates are derived in the following way: for ULIRG and PG/2MASS templates, the 5.8 and 8.0 μm fluxes are derived in the same manner as 5MUSES sources. The 24, 70, and 160 μm data points are derived by convolving the template SED at matching redshift with the MIPS 24, 70, and 160 μm filter response curves. For SINGS templates, we use directly the observed IRAC 5.8 and 8.0 μm photometry as the first two data points, which are essentially at rest frame for all SINGS objects. Then, we move the SINGS SEDs given by Dale et al. (2007) to the redshift of the 5MUSES source and derive the corresponding observed-frame MIPS 24, 70, and 160 μm photometry. During the SED fitting, we weight the data points by their wavelength since the majority of the energy is emitted at FIR for IR selected sources, and look for the template that fits each 5MUSES source best by minimizing the χ². A comparison of the ratio of flux densities at rest frame 5.8, 8.0 μm and the observed MIPS 24, 70, and 160 μm photometry from the source and the best-fit template can be found in Figure 2 (solid line). The dispersion in the ratio of the observed photometry over the photometry from the best-fit template (F_source/F_template) in each band is 0.07, 0.07, 0.03, 0.06, and 0.10 dex, respectively.

**Figure 2.** Histogram of the flux ratios between the source and the best-fit template, for galaxies with MIPS 70 and 160 μm detections (solid line) and for galaxies only with MIPS 70 μm detections (dashed line). The dotted and dash-dotted lines indicate the medians of the flux ratios for sources with 70 and 160 μm detections and sources with only 70 μm detections. All five bands appear to peak around a log[(F(source)/F(template)] ratio of 0 with rather narrow distributions. The 1σ deviations in F(source)/F(template) for the 5.8, 8.0, 24, and 70, 160 μm bands are 0.07, 0.07, 0.03, 0.06 and 0.10 dex, respectively, for sources with 70 and 160 μm detections and 0.07, 0.07, 0.03 and 0.07 dex for sources with only 70 μm detections.
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For sources with FIR detection only at MIPS 70 μm, we apply the same technique to fit the SED. We use the rest-frame IRAC 5.8 and 8.0 μm photometry and the observed MIPS 24 and 70 μm data in our fitting. The upper limit at 160 μm is used to exclude templates for which the synthetic photometry exceeds the 2σ upper limit of the source. A comparison of the ratio of flux densities at rest frame 5.8, 8.0 μm and the observed MIPS 24 and 70 μm photometry from the source and the best-fit template can be found in Figure 2 (dashed line). The dispersion in the ratio of F_source/F_template in each band is 0.07, 0.07, 0.03, and 0.07 dex, respectively.

Once the best-fit template is identified, we derive L_IR as explained in the last paragraph of the next section.

3.2.2. Sources without MIPS FIR Photometry

Nineteen objects do not have FIR detection even at 70 μm. For these sources, we select the IR SED based on the mid-IR spectra. Our method is to fit the IRS spectrum of the 5MUSES source with the mid-IR spectra of the templates in the corresponding wavelength regime and adopt the SED of the best-fit template. The templates of which the synthetic photometry exceed the 2σ upper limits at MIPS 70 and 160 μm bands are excluded. As will be shown in Section 3.2.3, this IRS-only method might underestimate the L_IR for cold sources by ∼20%, while it shows no significant offset for warm sources.¹⁶ All of the 19 objects in this category show SEDs with high (f_24 μm/f_70 μm)_obs ratios¹⁷; thus, they are more likely to be warm sources. This suggests that our approach of using the IRS spectrum to find the best-fit SED is unlikely to result in significant biases on L_IR.

Finally, for each source, we visually inspect the fitting results. We find that a range of templates could fit the SED well. We construct the final 5–1000 μm SED of a galaxy by combining its IRS spectrum in the mid-IR with the best-fit template SED at FIR. The total IR luminosity is derived by integrating under this SED curve. The uncertainty is derived from the standard deviation among the six best fits. We show examples of our SED fitting results in Figure 3 and the distribution of L_IR is shown Figure 4(a). We also show the distribution of L_IR for each type of objects, e.g., starburst, AGN, and composite (defined in detail in Section 4.1) in this figure. The derived L_IR for each source and its uncertainty is tabulated in Table 2. The distribution for the redshifts of 5MUSES objects is shown in Figure 4(b).

**Figure 3.** SEDs of a sample of nine 5MUSES sources. The final SED (black) is composed of the IRS spectrum in the mid-IR and the best-fit template in the FIR. The observed data are shown as red circles. The three sources in the top panel are fit with five data points (IRAC 5.8, 8.0 μm and MIPS 24, 70, and 160 μm). The three sources in the middle panel are fit with four data points (IRAC 5.8, 8.0 μm and MIPS 24 and 70 μm). The three sources in the bottom panel are fit with only the IRS spectra. The blue line is the mid-IR SED of the best-fit template for the sources fit with the IRS spectra.
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**Figure 4.** (a) Top panel: the distribution of the total infrared luminosity of the 5MUSES sample. The dotted line represents the whole sample with known redshift. The blue, yellow, and red solid lines represent the SB, composite, and AGN sources in the sample. The SBs and AGN dominate the lower and higher ends of the luminosity distribution, respectively. (b) Bottom panel: the distribution of the redshifts of the 5MUSES sample. The symbols are the same as in (a).
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Table 2. General Properties of the Sample

ID	Name	R.A. (J2000)	Decl. (J2000)	Redshift^a	$f_{24\rm \;\mu m}$ (mJy)	6.2 μm EW	log(L_IR/L_☉)
5MUSES-002	5MUSES_J021503.52-042421.6	02^h15^m035	−04^d24^m217	0.137(2)	5.2	0.776 ± 0.009	10.89 ± 0.02
5MUSES-004	5MUSES_J021557.11-033729.0	02^h15^m571	−03^d37^m291	0.032(2)	8.8	0.504 ± 0.048	9.80 ± 0.03
5MUSES-005	5MUSES_J021638.21-042250.8	02^h16^m382	−04^d22^m509	0.304(2)	14.4	<0.094	11.54 ± 0.02
5MUSES-006	5MUSES_J021640.72-044405.1	02^h16^m407	−04^d44^m051	0.870(1)	14.7	<0.045	12.70 ± 0.01
5MUSES-008	5MUSES_J021649.71-042554.8	02^h16^m497	−04^d25^m548	0.143(2)	10.1	1.107 ± 0.057	11.01 ± 0.07
5MUSES-009	5MUSES_J021657.77-032459.7	02^h16^m578	−03^d24^m598	0.137(1)	23.8	<0.062	10.90 ± 0.03
5MUSES-010	5MUSES_J021729.06-041937.8	02^h17^m291	−04^d19^m378	1.146(1)	8.8	<0.113	12.74 ± 0.06
5MUSES-011	5MUSES_J021743.01-043625.1	02^h17^m430	−04^d36^m252	0.784(2)	5.5	<0.080	12.00 ± 0.06
5MUSES-012	5MUSES_J021743.82-051751.7	02^h17^m438	−05^d17^m518	0.031(1)	17.1	0.645 ± 0.080	10.11 ± 0.03
5MUSES-013	5MUSES_J021754.88-035826.4	02^h17^m549	−03^d58^m265	0.226(1)	10.3	0.530 ± 0.044	11.72 ± 0.04
5MUSES-014	5MUSES_J021808.22-045845.3	02^h18^m082	−04^d58^m453	0.712(1)	9.1	<0.049	12.02 ± 0.07
5MUSES-016	5MUSES_J021830.57-045622.9	02^h18^m306	−04^d56^m230	1.401(1)	8.4	<0.083	12.67 ± 0.10
5MUSES-018	5MUSES_J021849.76-052158.2	02^h18^m498	−05^d21^m582	0.292(1)	5.3	0.571 ± 0.058	11.63 ± 0.03
5MUSES-019	5MUSES_J021859.74-040237.2	02^h18^m597	−04^d02^m372	0.199(2)	15.9	<0.160	11.23 ± 0.06
5MUSES-020	5MUSES_J021909.60-052512.9	02^h19^m096	−05^d25^m129	0.098(2)	25.3	<0.194	10.74 ± 0.02
5MUSES-021	5MUSES_J021912.71-050541.8	02^h19^m127	−05^d05^m419	0.194(2)	6.1	0.639 ± 0.041	11.04 ± 0.07
5MUSES-022	5MUSES_J021916.05-055726.9	02^h19^m161	−05^d57^m270	0.103(2)	11.0	0.198 ± 0.027	10.71 ± 0.05
5MUSES-023	5MUSES_J021928.33-042239.8	02^h19^m283	−04^d22^m398	0.042(2)	17.3	0.611 ± 0.053	10.04 ± 0.04
5MUSES-025	5MUSES_J021938.70-032508.2	02^h19^m387	−03^d25^m083	0.435(2)	6.8	<0.094	11.66 ± 0.02
5MUSES-026	5MUSES_J021939.08-051133.8	02^h19^m391	−05^d11^m339	0.151(2)	32.5	0.101 ± 0.010	11.38 ± 0.06
5MUSES-028	5MUSES_J021953.04-051824.1	02^h19^m530	−05^d18^m242	0.072(2)	30.3	0.781 ± 0.019	10.93 ± 0.03
5MUSES-029	5MUSES_J021956.96-052440.4	02^h19^m570	−05^d24^m405	0.081(2)	5.6	0.699 ± 0.079	10.44 ± 0.04
5MUSES-030	5MUSES_J022000.22-043947.6	02^h20^m002	−04^d39^m477	0.350(1)	5.8	0.137 ± 0.007	11.48 ± 0.06
5MUSES-031	5MUSES_J022005.93-031545.7	02^h20^m059	−03^d15^m458	1.560(2)	6.9	<0.178	13.17 ± 0.05
5MUSES-032	5MUSES_J022012.21-034111.8	02^h20^m122	−03^d41^m118	0.166(2)	6.7	<0.079	10.40 ± 0.08
5MUSES-034	5MUSES_J022145.09-053207.4	02^h21^m451	−05^d32^m074	0.008(2)	6.2	0.391 ± 0.049	8.16 ± 0.05
5MUSES-035	5MUSES_J022147.82-025730.7	02^h21^m478	−02^d57^m307	0.068(2)	21.0	0.714 ± 0.037	10.88 ± 0.04
5MUSES-036	5MUSES_J022147.87-044613.5	02^h21^m479	−04^d46^m135	0.025(2)	5.1	0.809 ± 0.035	9.15 ± 0.02
5MUSES-037	5MUSES_J022151.54-032911.8	02^h21^m515	−03^d29^m118	0.164(1)	6.9	0.748 ± 0.104	11.14 ± 0.03
5MUSES-038	5MUSES_J022205.03-050537.0	02^h22^m050	−05^d05^m370	0.258(2)	6.3	0.696 ± 0.035	11.68 ± 0.04
5MUSES-039	5MUSES_J022223.26-044319.8	02^h22^m233	−04^d43^m199	0.073(2)	5.1	0.356 ± 0.023	10.28 ± 0.03
5MUSES-040	5MUSES_J022224.06-050550.3	02^h22^m241	−05^d05^m504	0.149(2)	5.7	0.602 ± 0.022	10.95 ± 0.02
5MUSES-041	5MUSES_J022241.34-045652.0	02^h22^m413	−04^d56^m521	0.139(2)	5.1	0.308 ± 0.008	10.57 ± 0.08
5MUSES-043	5MUSES_J022257.96-041840.8	02^h22^m580	−04^d18^m408	0.239(2)	5.3	0.205 ± 0.013	11.18 ± 0.05
5MUSES-044	5MUSES_J022301.97-052335.8	02^h23^m020	−05^d23^m359	0.708(2)	6.8	<0.054	12.77 ± 0.04
5MUSES-045	5MUSES_J022309.31-052316.1	02^h23^m093	−05^d23^m162	0.084(2)	5.3	<0.426	9.93 ± 0.06
5MUSES-047	5MUSES_J022315.58-040606.0	02^h23^m156	−04^d06^m060	0.199(2)	9.4	0.486 ± 0.067	11.31 ± 0.04
5MUSES-048	5MUSES_J022329.13-043209.5	02^h23^m291	−04^d32^m096	0.144(2)	7.6	0.585 ± 0.075	10.95 ± 0.05
5MUSES-049	5MUSES_J022334.65-035229.4	02^h23^m347	−03^d52^m294	0.176(2)	7.6	0.966 ± 0.129	11.03 ± 0.10
5MUSES-050	5MUSES_J022345.04-054234.4	02^h23^m450	−05^d42^m345	0.143(2)	9.1	0.689 ± 0.003	11.17 ± 0.02
5MUSES-051	5MUSES_J022356.49-025431.1	02^h23^m565	−02^d54^m311	0.451(2)	10.4	0.058 ± 0.004	11.79 ± 0.07
5MUSES-052	5MUSES_J022413.64-042227.8	02^h24^m136	−04^d22^m278	0.116(2)	9.2	0.626 ± 0.062	10.96 ± 0.04
5MUSES-053	5MUSES_J022422.48-040230.5	02^h24^m225	−04^d02^m306	0.171(2)	7.5	0.414 ± 0.007	11.16 ± 0.04
5MUSES-054	5MUSES_J022431.58-052818.8	02^h24^m316	−05^d28^m188	2.068(2)	9.4	⋅⋅⋅	13.02 ± 0.25
5MUSES-055	5MUSES_J022434.28-041531.2	02^h24^m343	−04^d15^m312	0.259(2)	6.3	0.584 ± 0.019	11.58 ± 0.02
5MUSES-056	5MUSES_J022438.97-042706.3	02^h24^m390	−04^d27^m064	0.252(2)	6.6	0.156 ± 0.034	11.30 ± 0.06
5MUSES-057	5MUSES_J022446.99-040851.3	02^h24^m470	−04^d08^m514	0.096(2)	5.3	0.456 ± 0.012	10.81 ± 0.01
5MUSES-058	5MUSES_J022457.64-041417.9	02^h24^m576	−04^d14^m180	0.063(2)	11.9	0.476 ± 0.035	10.59 ± 0.04
5MUSES-060	5MUSES_J022507.43-041835.7	02^h25^m074	−04^d18^m358	0.105(2)	6.8	0.632 ± 0.062	10.56 ± 0.05
5MUSES-061	5MUSES_J022508.33-053917.7	02^h25^m083	−05^d39^m177	0.293(2)	9.6	0.025 ± 0.002	11.55 ± 0.05
5MUSES-062	5MUSES_J022522.59-045452.2	02^h25^m226	−04^d54^m522	0.144(2)	10.1	0.719 ± 0.007	11.25 ± 0.02
5MUSES-063	5MUSES_J022536.44-050011.5	02^h25^m364	−05^d00^m116	0.053(1)	13.7	0.709 ± 0.051	10.77 ± 0.11
5MUSES-064	5MUSES_J022548.21-050051.5	02^h25^m482	−05^d00^m515	0.150(1)	8.0	0.297 ± 0.051	11.19 ± 0.04
5MUSES-065	5MUSES_J022549.78-040024.6	02^h25^m498	−04^d00^m247	0.044(2)	58.5	0.438 ± 0.009	10.64 ± 0.03
5MUSES-066	5MUSES_J022559.99-050145.3	02^h26^m000	−05^d01^m453	0.205(2)	5.7	0.916 ± 0.027	11.39 ± 0.04
5MUSES-067	5MUSES_J022602.92-045306.8	02^h26^m029	−04^d53^m068	0.056(2)	6.4	0.669 ± 0.028	10.13 ± 0.03
5MUSES-068	5MUSES_J022603.61-045903.8	02^h26^m036	−04^d59^m038	0.055(2)	31.4	0.634 ± 0.047	10.59 ± 0.04
5MUSES-069	5MUSES_J022617.43-050443.4	02^h26^m174	−05^d04^m435	0.057(2)	48.7	0.168 ± 0.005	10.77 ± 0.04
5MUSES-070	5MUSES_J022637.79-035841.6	02^h26^m378	−03^d58^m417	0.070(2)	13.5	0.377 ± 0.019	10.43 ± 0.04
5MUSES-071	5MUSES_J022655.87-040302.2	02^h26^m559	−04^d03^m025	0.135(2)	6.9	1.026 ± 0.179	10.59 ± 0.05
5MUSES-073	5MUSES_J022720.68-044537.1	02^h27^m207	−04^d45^m372	0.055(2)	73.1	0.625 ± 0.032	11.06 ± 0.04
5MUSES-074	5MUSES_J022738.53-044702.7	02^h27^m385	−04^d47^m028	0.173(2)	7.1	0.918 ± 0.032	11.13 ± 0.03
5MUSES-075	5MUSES_J022741.64-045650.5	02^h27^m416	−04^d56^m506	0.055(2)	11.4	0.627 ± 0.004	10.53 ± 0.03
5MUSES-077	5MUSES_J103237.44+580845.9	10^h32^m374	+58^d08^m460	0.251(2)	6.1	0.394 ± 0.060	11.74 ± 0.04
5MUSES-079	5MUSES_J103450.50+584418.2	10^h34^m505	+58^d44^m182	0.091(1)	20.1	0.643 ± 0.047	10.90 ± 0.06
5MUSES-080	5MUSES_J103513.72+573444.6	10^h35^m137	+57^d34^m446	1.537(2)	5.5	<0.171	13.25 ± 0.08
5MUSES-081	5MUSES_J103527.20+583711.9	10^h35^m272	+58^d37^m120	0.885(2)	6.9	0.080 ± 0.010	12.53 ± 0.04
5MUSES-082	5MUSES_J103531.46+581234.2	10^h35^m315	+58^d12^m342	0.176(2)	5.0	0.574 ± 0.018	11.25 ± 0.04
5MUSES-083	5MUSES_J103542.76+583313.1	10^h35^m428	+58^d33^m131	0.087(2)	6.6	0.761 ± 0.002	10.51 ± 0.06
5MUSES-084	5MUSES_J103601.81+581836.2	10^h36^m018	+58^d18^m362	0.100(1)	6.0	0.421 ± 0.012	10.63 ± 0.04
5MUSES-085	5MUSES_J103606.45+581829.7	10^h36^m065	+58^d18^m297	0.210(1)	22.5	<0.068	11.41 ± 0.02
5MUSES-086	5MUSES_J103646.42+584330.6	10^h36^m464	+58^d43^m306	0.140(2)	6.8	0.549 ± 0.020	10.94 ± 0.03
5MUSES-087	5MUSES_J103701.99+574414.8	10^h37^m020	+57^d44^m148	0.577(2)	12.8	<0.065	12.06 ± 0.05
5MUSES-088	5MUSES_J103724.74+580512.9	10^h37^m247	+58^d05^m129	1.517(1)	8.6	<0.158	13.02 ± 0.06
5MUSES-089	5MUSES_J103803.35+572701.5	10^h38^m034	+57^d27^m015	1.285(2)	15.4	<0.086	13.33 ± 0.06
5MUSES-090	5MUSES_J103813.90+580047.3	10^h38^m139	+58^d00^m474	0.205(2)	6.2	<0.335	10.89 ± 0.14
5MUSES-091	5MUSES_J103818.19+583556.5	10^h38^m182	+58^d35^m565	0.129(2)	7.8	0.312 ± 0.018	10.50 ± 0.03
5MUSES-093	5MUSES_J103856.16+570333.9	10^h38^m562	+57^d03^m339	0.178(2)	5.7	0.338 ± 0.011	10.82 ± 0.03
5MUSES-097	5MUSES_J104016.32+570846.0	10^h40^m163	+57^d08^m461	0.118(2)	5.2	0.661 ± 0.003	10.87 ± 0.02
5MUSES-098	5MUSES_J104058.79+581703.3	10^h40^m588	+58^d17^m034	0.072(1)	10.4	<0.119	9.96 ± 0.06
5MUSES-099	5MUSES_J104131.79+592258.4	10^h41^m318	+59^d22^m584	0.925(1)	7.0	<0.061	12.16 ± 0.09
5MUSES-100	5MUSES_J104132.49+565953.0	10^h41^m325	+56^d59^m530	0.346(1)	8.3	0.454 ± 0.044	11.74 ± 0.04
5MUSES-101	5MUSES_J104159.83+585856.4	10^h41^m598	+58^d58^m564	0.360(2)	21.7	<0.127	11.95 ± 0.02
5MUSES-102	5MUSES_J104255.66+575549.7	10^h42^m557	+57^d55^m498	1.468(1)	6.4	<0.067	13.01 ± 0.05
5MUSES-103	5MUSES_J104303.50+585718.1	10^h43^m035	+58^d57^m181	0.595(1)	5.4	<0.066	11.90 ± 0.05
5MUSES-105	5MUSES_J104432.94+564041.6	10^h44^m329	+56^d40^m416	0.067(1)	28.7	0.637 ± 0.117	10.92 ± 0.03
5MUSES-106	5MUSES_J104438.21+562210.7	10^h44^m382	+56^d22^m108	0.025(1)	80.6	0.509 ± 0.027	10.49 ± 0.05
5MUSES-107	5MUSES_J104454.08+574425.7	10^h44^m541	+57^d44^m258	0.118(1)	6.5	0.585 ± 0.096	10.99 ± 0.02
5MUSES-108	5MUSES_J104501.73+571111.3	10^h45^m017	+57^d11^m114	0.390(1)	10.9	<0.164	11.60 ± 0.05
5MUSES-109	5MUSES_J104516.02+592304.7	10^h45^m160	+59^d23^m047	0.322(1)	5.1	0.094 ± 0.005	11.39 ± 0.07
5MUSES-110	5MUSES_J104643.26+584715.1	10^h46^m433	+58^d47^m151	0.140(1)	5.4	0.522 ± 0.017	10.90 ± 0.03
5MUSES-112	5MUSES_J104705.07+590728.4	10^h47^m051	+59^d07^m285	0.391(1)	7.0	0.032 ± 0.003	11.39 ± 0.10
5MUSES-114	5MUSES_J104729.89+572842.9	10^h47^m299	+57^d28^m429	0.230(2)	6.2	0.477 ± 0.052	11.60 ± 0.01
5MUSES-115	5MUSES_J104837.81+582642.1	10^h48^m378	+58^d26^m422	0.232(1)	7.6	0.729 ± 0.022	11.68 ± 0.02
5MUSES-116	5MUSES_J104839.73+555356.4	10^h48^m397	+55^d53^m565	2.043(1)	9.8	⋅⋅⋅	13.46 ± 0.25
5MUSES-117	5MUSES_J104843.90+580341.2	10^h48^m439	+58^d03^m413	0.162(2)	7.1	0.838 ± 0.029	11.04 ± 0.05
5MUSES-118	5MUSES_J104907.15+565715.3	10^h49^m072	+56^d57^m154	0.072(1)	9.7	0.805 ± 0.014	10.65 ± 0.03
5MUSES-119	5MUSES_J104918.33+562512.9	10^h49^m183	+56^d25^m130	0.330(1)	7.1	0.037 ± 0.001	11.20 ± 0.08
5MUSES-123	5MUSES_J105005.97+561500.0	10^h50^m060	+56^d15^m000	0.119(2)	14.8	0.714 ± 0.097	11.14 ± 0.04
5MUSES-124	5MUSES_J105047.83+590348.3	10^h50^m478	+59^d03^m484	0.131(2)	5.2	0.623 ± 0.015	10.90 ± 0.04
5MUSES-126	5MUSES_J105058.76+560550.0	10^h50^m588	+56^d05^m500	0.125(2)	5.5	0.496 ± 0.054	10.41 ± 0.05
5MUSES-127	5MUSES_J105106.12+591625.3	10^h51^m061	+59^d16^m253	0.768(1)	5.4	0.078 ± 0.003	12.32 ± 0.06
5MUSES-128	5MUSES_J105128.05+573502.4	10^h51^m281	+57^d35^m024	0.073(1)	10.0	0.695 ± 0.081	10.42 ± 0.03
5MUSES-130	5MUSES_J105158.53+590652.0	10^h51^m585	+59^d06^m521	1.814(2)	5.4	<0.093	13.26 ± 0.05
5MUSES-131	5MUSES_J105200.29+591933.7	10^h52^m003	+59^d19^m338	0.115(1)	11.4	0.297 ± 0.036	10.76 ± 0.03
5MUSES-132	5MUSES_J105206.56+580947.1	10^h52^m066	+58^d09^m471	0.117(2)	16.7	0.661 ± 0.009	11.34 ± 0.03
5MUSES-133	5MUSES_J105336.87+580350.7	10^h53^m369	+58^d03^m507	0.460(1)	5.9	0.368 ± 0.001	12.02 ± 0.04
5MUSES-135	5MUSES_J105404.11+574019.7	10^h54^m041	+57^d40^m197	1.101(1)	8.5	<0.084	12.70 ± 0.03
5MUSES-136	5MUSES_J105421.65+582344.6	10^h54^m217	+58^d23^m447	0.205(2)	16.8	0.074 ± 0.001	11.43 ± 0.03
5MUSES-138	5MUSES_J105604.84+574229.9	10^h56^m048	+57^d42^m300	1.211(1)	11.2	<0.146	13.16 ± 0.11
5MUSES-139	5MUSES_J105636.95+573449.3	10^h56^m370	+57^d34^m494	0.047(1)	6.4	0.444 ± 0.060	10.16 ± 0.04
5MUSES-140	5MUSES_J105641.81+580046.0	10^h56^m418	+58^d00^m460	0.130(1)	7.5	0.686 ± 0.014	11.03 ± 0.03
5MUSES-141	5MUSES_J105705.43+580437.4	10^h57^m054	+58^d04^m374	0.140(2)	16.5	0.097 ± 0.001	11.18 ± 0.03
5MUSES-142	5MUSES_J105733.53+565737.4	10^h57^m335	+56^d57^m375	0.086(1)	5.6	0.454 ± 0.023	10.38 ± 0.06
5MUSES-143	5MUSES_J105740.55+570616.4	10^h57^m406	+57^d06^m165	0.073(1)	6.1	0.503 ± 0.058	10.24 ± 0.03
5MUSES-144	5MUSES_J105829.28+580439.2	10^h58^m293	+58^d04^m393	0.136(1)	7.1	0.452 ± 0.075	10.56 ± 0.03
5MUSES-145	5MUSES_J105854.08+574130.0	10^h58^m541	+57^d41^m300	0.232(1)	6.1	0.222 ± 0.031	11.10 ± 0.07
5MUSES-146	5MUSES_J105903.47+572155.1	10^h59^m035	+57^d21^m551	0.119(2)	13.8	<0.261	10.87 ± 0.05
5MUSES-147	5MUSES_J105951.71+581802.9	10^h59^m517	+58^d18^m029	2.335(1)	5.3	⋅⋅⋅	13.08 ± 0.17
5MUSES-148	5MUSES_J105959.95+574848.1	11^h00^m000	+57^d48^m482	0.453(1)	9.1	<0.052	11.83 ± 0.02
5MUSES-149	5MUSES_J110002.06+573142.1	11^h00^m021	+57^d31^m422	0.387(2)	8.3	0.496 ± 0.027	12.02 ± 0.05
5MUSES-151	5MUSES_J110124.97+574315.8	11^h01^m250	+57^d43^m159	0.243(1)	6.1	0.545 ± 0.058	11.17 ± 0.06
5MUSES-152	5MUSES_J110133.80+575206.6	11^h01^m338	+57^d52^m066	0.277(2)	6.4	0.509 ± 0.057	11.84 ± 0.04
5MUSES-153	5MUSES_J110223.58+574436.2	11^h02^m236	+57^d44^m362	0.226(1)	10.2	<0.093	11.12 ± 0.02
5MUSES-154	5MUSES_J110235.02+574655.7	11^h02^m350	+57^d46^m557	0.226(2)	6.2	0.523 ± 0.066	11.48 ± 0.04
5MUSES-155	5MUSES_J155833.00+544426.9	15^h58^m329	+54^d44^m272	0.350(1)	9.1	0.086 ± 0.001	11.52 ± 0.03
5MUSES-156	5MUSES_J155833.28+545937.1	15^h58^m333	+54^d59^m372	0.340(2)	6.3	0.327 ± 0.012	12.10 ± 0.03
5MUSES-157	5MUSES_J155936.12+544203.7	15^h59^m361	+54^d42^m038	0.308(2)	14.5	<0.060	11.32 ± 0.06
5MUSES-158	5MUSES_J160038.82+551018.6	16^h00^m388	+55^d10^m187	0.144(2)	20.1	0.637 ± 0.020	11.45 ± 0.04
5MUSES-160	5MUSES_J160114.49+551304.1	16^h01^m145	+55^d13^m041	0.220(2)	7.9	<0.079	10.82 ± 0.06
5MUSES-162	5MUSES_J160128.52+544521.3	16^h01^m285	+54^d45^m214	0.728(1)	12.8	<0.034	12.47 ± 0.01
5MUSES-163	5MUSES_J160322.77+544237.3	16^h03^m228	+54^d42^m373	0.215(1)	5.7	0.687 ± 0.070	11.35 ± 0.03
5MUSES-165	5MUSES_J160341.30+552612.7	16^h03^m413	+55^d26^m127	0.146(1)	5.3	0.610 ± 0.012	11.11 ± 0.03
5MUSES-166	5MUSES_J160358.18+555504.4	16^h03^m582	+55^d55^m044	0.322(2)	5.0	0.406 ± 0.030	11.56 ± 0.06
5MUSES-167	5MUSES_J160401.21+551502.7	16^h04^m012	+55^d15^m027	0.182(1)	11.4	<0.112	11.11 ± 0.05
5MUSES-168	5MUSES_J160408.18+542531.2	16^h04^m082	+54^d25^m312	0.260(1)	5.0	0.604 ± 0.054	11.54 ± 0.02
5MUSES-169	5MUSES_J160408.30+545813.0	16^h04^m083	+54^d58^m131	0.064(1)	26.2	0.602 ± 0.009	10.83 ± 0.03
5MUSES-171	5MUSES_J160440.64+553409.2	16^h04^m406	+55^d34^m093	0.078(1)	22.9	0.521 ± 0.035	11.10 ± 0.04
5MUSES-173	5MUSES_J160630.59+542007.4	16^h06^m306	+54^d20^m074	0.820(1)	5.5	<0.052	11.91 ± 0.10
5MUSES-174	5MUSES_J160655.35+534016.9	16^h06^m554	+53^d40^m169	0.214(1)	14.6	<0.086	11.26 ± 0.01
5MUSES-176	5MUSES_J160730.41+554905.5	16^h07^m304	+55^d49^m056	0.118(1)	6.2	0.835 ± 0.100	10.81 ± 0.03
5MUSES-177	5MUSES_J160743.09+554416.5	16^h07^m431	+55^d44^m165	0.118(1)	9.6	0.752 ± 0.049	11.13 ± 0.03
5MUSES-178	5MUSES_J160801.79+555359.7	16^h08^m018	+55^d53^m597	0.062(1)	6.2	1.057 ± 0.011	10.24 ± 0.04
5MUSES-179	5MUSES_J160803.71+545301.9	16^h08^m037	+54^d53^m020	0.053(1)	5.1	0.373 ± 0.019	10.26 ± 0.01
5MUSES-180	5MUSES_J160819.57+553314.2	16^h08^m196	+55^d33^m143	0.115(1)	7.2	0.337 ± 0.005	10.83 ± 0.02
5MUSES-181	5MUSES_J160832.59+552926.9	16^h08^m326	+55^d29^m270	0.065(1)	5.9	0.844 ± 0.121	10.32 ± 0.03
5MUSES-183	5MUSES_J160839.73+552330.6	16^h08^m397	+55^d23^m307	0.064(1)	5.8	0.964 ± 0.029	10.33 ± 0.02
5MUSES-184	5MUSES_J160847.02+563702.2	16^h08^m470	+56^d37^m022	0.590(1)	8.3	0.045 ± 0.001	12.21 ± 0.02
5MUSES-185	5MUSES_J160858.38+553010.2	16^h08^m584	+55^d30^m103	0.066(1)	8.8	0.586 ± 0.104	10.34 ± 0.02
5MUSES-186	5MUSES_J160858.66+563635.6	16^h08^m587	+56^d36^m357	0.117(1)	5.0	0.566 ± 0.050	10.77 ± 0.04
5MUSES-187	5MUSES_J160907.56+552428.4	16^h09^m076	+55^d24^m284	0.065(1)	7.7	0.670 ± 0.003	10.54 ± 0.03
5MUSES-188	5MUSES_J160908.28+552241.4	16^h09^m083	+55^d22^m415	0.084(1)	6.6	0.824 ± 0.056	10.65 ± 0.02
5MUSES-189	5MUSES_J160926.69+551642.3	16^h09^m267	+55^d16^m423	0.068(2)	6.8	0.507 ± 0.058	10.19 ± 0.02
5MUSES-190	5MUSES_J160930.53+563509.0	16^h09^m305	+56^d35^m091	0.030(1)	5.1	0.428 ± 0.028	9.22 ± 0.06
5MUSES-191	5MUSES_J160931.55+541827.3	16^h09^m316	+54^d18^m274	0.082(1)	5.6	0.497 ± 0.033	10.61 ± 0.04
5MUSES-192	5MUSES_J160937.48+541259.2	16^h09^m375	+54^d12^m593	0.086(1)	5.7	0.681 ± 0.018	10.66 ± 0.02
5MUSES-193	5MUSES_J161103.73+544322.0	16^h11^m037	+54^d43^m221	0.063(2)	6.6	0.536 ± 0.018	10.26 ± 0.03
5MUSES-194	5MUSES_J161119.36+553355.4	16^h11^m194	+55^d33^m554	0.227(1)	35.4	<0.100	11.76 ± 0.03
5MUSES-195	5MUSES_J161123.44+545158.2	16^h11^m234	+54^d51^m582	0.078(2)	5.5	0.516 ± 0.002	10.40 ± 0.03
5MUSES-196	5MUSES_J161223.39+540339.2	16^h12^m234	+54^d03^m392	0.138(2)	13.0	0.839 ± 0.136	11.07 ± 0.03
5MUSES-197	5MUSES_J161233.43+545630.4	16^h12^m334	+54^d56^m305	0.083(1)	8.3	0.560 ± 0.083	10.66 ± 0.04
5MUSES-198	5MUSES_J161241.05+543956.8	16^h12^m411	+54^d39^m568	0.035(2)	5.7	0.841 ± 0.078	9.51 ± 0.03
5MUSES-199	5MUSES_J161249.54+564232.7	16^h12^m495	+56^d42^m328	0.336(1)	8.0	0.411 ± 0.036	11.60 ± 0.08
5MUSES-200	5MUSES_J161250.85+532304.9	16^h12^m509	+53^d23^m050	0.048(2)	17.9	0.405 ± 0.074	10.40 ± 0.05
5MUSES-202	5MUSES_J161254.17+545525.4	16^h12^m542	+54^d55^m254	0.065(2)	8.0	0.624 ± 0.015	10.59 ± 0.01
5MUSES-203	5MUSES_J161301.82+552123.0	16^h13^m018	+55^d21^m231	0.012(2)	36.3	0.563 ± 0.044	9.47 ± 0.05
5MUSES-204	5MUSES_J161357.01+534105.3	16^h13^m570	+53^d41^m053	0.180(2)	6.5	0.106 ± 0.004	10.83 ± 0.03
5MUSES-205	5MUSES_J161402.98+560756.9	16^h14^m030	+56^d07^m570	0.063(2)	21.0	0.746 ± 0.052	10.79 ± 0.06
5MUSES-207	5MUSES_J161406.87+551451.9	16^h14^m069	+55^d14^m520	0.564(2)	9.2	0.047 ± 0.010	12.18 ± 0.03
5MUSES-208	5MUSES_J161411.52+540554.3	16^h14^m115	+54^d05^m543	0.305(1)	5.9	0.587 ± 0.123	11.72 ± 0.04
5MUSES-209	5MUSES_J161449.08+554512.9	16^h14^m491	+55^d45^m129	0.064(1)	15.0	0.148 ± 0.007	10.26 ± 0.03
5MUSES-210	5MUSES_J161521.78+543148.3	16^h15^m218	+54^d31^m483	0.474(1)	5.1	<0.058	11.47 ± 0.08
5MUSES-211	5MUSES_J161528.07+534402.4	16^h15^m281	+53^d44^m025	0.133(2)	6.0	0.476 ± 0.071	11.01 ± 0.03
5MUSES-212	5MUSES_J161542.10+561814.7	16^h15^m421	+56^d18^m147	0.109(1)	13.7	<0.150	10.67 ± 0.04
5MUSES-214	5MUSES_J161546.51+550330.9	16^h15^m465	+55^d03^m310	0.087(1)	8.9	0.169 ± 0.003	10.26 ± 0.03
5MUSES-215	5MUSES_J161548.31+534551.1	16^h15^m483	+53^d45^m511	0.147(1)	7.5	0.512 ± 0.104	11.18 ± 0.03
5MUSES-216	5MUSES_J161551.45+541535.9	16^h15^m515	+54^d15^m360	0.215(2)	6.3	0.445 ± 0.049	11.43 ± 0.04
5MUSES-217	5MUSES_J161644.45+533734.0	16^h16^m444	+53^d37^m343	0.147(1)	8.8	0.828 ± 0.080	11.19 ± 0.02
5MUSES-219	5MUSES_J161645.92+542554.4	16^h16^m459	+54^d25^m544	0.223(1)	12.4	0.162 ± 0.002	11.26 ± 0.02
5MUSES-220	5MUSES_J161655.96+545307.0	16^h16^m560	+54^d53^m071	0.418(1)	5.1	0.391 ± 0.039	11.81 ± 0.05
5MUSES-221	5MUSES_J161659.95+560027.2	16^h17^m000	+56^d00^m272	0.063(1)	10.8	0.517 ± 0.049	10.66 ± 0.02
5MUSES-222	5MUSES_J161712.27+551853.0	16^h17^m123	+55^d18^m530	0.037(1)	6.7	0.714 ± 0.030	9.53 ± 0.06
5MUSES-223	5MUSES_J161716.57+550920.3	16^h17^m166	+55^d09^m203	0.092(2)	7.3	0.728 ± 0.022	10.65 ± 0.04
5MUSES-225	5MUSES_J161748.06+551831.1	16^h17^m481	+55^d18^m311	0.145(1)	7.0	0.363 ± 0.030	11.13 ± 0.05
5MUSES-227	5MUSES_J161759.22+541501.3	16^h17^m592	+54^d15^m013	0.135(1)	22.7	0.137 ± 0.006	11.12 ± 0.06
5MUSES-228	5MUSES_J161809.36+551522.0	16^h18^m094	+55^d15^m221	0.136(1)	6.4	0.137 ± 0.002	10.71 ± 0.05
5MUSES-229	5MUSES_J161819.31+541859.0	16^h18^m193	+54^d18^m591	0.083(1)	28.3	0.472 ± 0.005	11.14 ± 0.04
5MUSES-230	5MUSES_J161823.11+552721.4	16^h18^m231	+55^d27^m214	0.084(1)	25.3	0.613 ± 0.016	11.13 ± 0.03
5MUSES-231	5MUSES_J161827.72+552208.6	16^h18^m277	+55^d22^m086	0.083(1)	9.9	0.673 ± 0.082	10.74 ± 0.05
5MUSES-232	5MUSES_J161843.35+554433.1	16^h18^m434	+55^d44^m331	0.153(1)	10.1	0.618 ± 0.046	11.29 ± 0.03
5MUSES-233	5MUSES_J161848.03+535837.5	16^h18^m480	+53^d58^m376	0.079(1)	7.2	0.124 ± 0.005	10.49 ± 0.09
5MUSES-234	5MUSES_J161929.57+541841.9	16^h19^m296	+54^d18^m419	0.100(1)	16.5	0.487 ± 0.048	11.07 ± 0.02
5MUSES-235	5MUSES_J161950.52+543715.3	16^h19^m505	+54^d37^m154	0.146(1)	7.0	0.761 ± 0.041	11.14 ± 0.03
5MUSES-239	5MUSES_J162033.98+542323.5	16^h20^m340	+54^d23^m235	0.133(1)	9.1	0.622 ± 0.058	11.07 ± 0.05
5MUSES-240	5MUSES_J162038.10+553521.4	16^h20^m381	+55^d35^m215	0.191(1)	8.6	0.716 ± 0.099	11.39 ± 0.03
5MUSES-241	5MUSES_J162058.82+542513.1	16^h20^m588	+54^d25^m132	0.082(1)	21.3	0.880 ± 0.005	11.11 ± 0.03
5MUSES-242	5MUSES_J162059.02+542601.5	16^h20^m590	+54^d26^m015	0.046(1)	17.2	0.732 ± 0.068	10.20 ± 0.07
5MUSES-243	5MUSES_J162110.51+544116.8	16^h21^m105	+54^d41^m168	0.155(1)	9.0	0.175 ± 0.008	10.92 ± 0.06
5MUSES-244	5MUSES_J162127.98+551452.9	16^h21^m280	+55^d14^m529	0.100(1)	5.6	0.707 ± 0.091	10.74 ± 0.02
5MUSES-245	5MUSES_J162133.00+551829.9	16^h21^m330	+55^d18^m299	0.238(1)	7.7	0.494 ± 0.081	11.27 ± 0.13
5MUSES-247	5MUSES_J162150.85+553008.8	16^h21^m509	+55^d30^m089	0.099(1)	6.6	0.911 ± 0.009	10.82 ± 0.02
5MUSES-248	5MUSES_J162210.87+550253.7	16^h22^m109	+55^d02^m538	0.034(1)	47.7	0.527 ± 0.062	10.58 ± 0.04
5MUSES-249	5MUSES_J162214.77+550614.1	16^h22^m148	+55^d06^m142	0.237(1)	7.4	0.470 ± 0.021	11.67 ± 0.02
5MUSES-250	5MUSES_J162313.11+551111.5	16^h23^m131	+55^d11^m116	0.236(1)	6.6	0.405 ± 0.001	11.67 ± 0.02
5MUSES-251	5MUSES_J163001.46+410952.9	16^h30^m015	+41^d09^m529	0.121(1)	7.3	0.697 ± 0.127	10.84 ± 0.01
5MUSES-252	5MUSES_J163111.27+404805.2	16^h31^m113	+40^d48^m052	0.258(1)	16.7	0.042 ± 0.002	11.30 ± 0.24
5MUSES-253	5MUSES_J163128.57+404536.0	16^h31^m286	+40^d45^m360	0.181(1)	14.8	0.170 ± 0.009	11.13 ± 0.04
5MUSES-254	5MUSES_J163220.40+402334.4	16^h32^m204	+40^d23^m344	0.079(1)	8.3	0.602 ± 0.002	10.79 ± 0.05
5MUSES-255	5MUSES_J163308.28+403321.5	16^h33^m083	+40^d33^m216	0.404(1)	8.3	0.164 ± 0.013	11.82 ± 0.05
5MUSES-256	5MUSES_J163310.92+405641.3	16^h33^m109	+40^d56^m414	0.136(1)	8.0	0.725 ± 0.022	10.86 ± 0.03
5MUSES-258	5MUSES_J163317.57+403443.6	16^h33^m176	+40^d34^m436	0.378(1)	7.2	<0.073	11.46 ± 0.03
5MUSES-260	5MUSES_J163335.85+401529.1	16^h33^m359	+40^d15^m291	0.028(1)	30.3	0.954 ± 0.037	10.07 ± 0.04
5MUSES-261	5MUSES_J163359.12+405304.7	16^h33^m591	+40^d53^m047	0.032(1)	11.9	0.474 ± 0.027	9.92 ± 0.03
5MUSES-262	5MUSES_J163401.79+412052.5	16^h34^m018	+41^d20^m526	0.028(1)	47.0	0.739 ± 0.030	10.32 ± 0.04
5MUSES-263	5MUSES_J163506.06+411038.4	16^h35^m061	+41^d10^m385	0.079(1)	13.5	0.462 ± 0.001	10.83 ± 0.03
5MUSES-264	5MUSES_J163541.68+405900.6	16^h35^m417	+40^d59^m007	0.188(1)	10.4	<0.189	11.04 ± 0.03
5MUSES-265	5MUSES_J163546.87+403903.6	16^h35^m469	+40^d39^m036	0.122(1)	8.3	0.613 ± 0.007	11.09 ± 0.03
5MUSES-266	5MUSES_J163608.13+410507.6	16^h36^m081	+41^d05^m077	0.170(1)	13.2	0.457 ± 0.010	11.91 ± 0.10
5MUSES-267	5MUSES_J163645.27+415133.6	16^h36^m453	+41^d51^m337	0.081(1)	7.8	<0.190	10.24 ± 0.06
5MUSES-268	5MUSES_J163651.65+405600.1	16^h36^m517	+40^d56^m002	0.476(1)	9.6	<0.101	11.83 ± 0.02
5MUSES-269	5MUSES_J163705.29+413155.8	16^h37^m053	+41^d31^m559	0.122(2)	10.6	0.704 ± 0.001	11.20 ± 0.03
5MUSES-270	5MUSES_J163709.31+414030.8	16^h37^m093	+41^d40^m309	0.760(1)	9.5	<0.032	12.41 ± 0.05
5MUSES-271	5MUSES_J163715.58+414933.7	16^h37^m156	+41^d49^m337	0.121(1)	8.8	0.580 ± 0.012	10.95 ± 0.03
5MUSES-272	5MUSES_J163729.26+405248.5	16^h37^m293	+40^d52^m485	0.026(2)	19.1	0.406 ± 0.020	10.10 ± 0.04
5MUSES-273	5MUSES_J163731.41+405155.5	16^h37^m314	+40^d51^m556	0.189(1)	7.6	0.404 ± 0.045	11.44 ± 0.05
5MUSES-274	5MUSES_J163751.24+401439.9	16^h37^m512	+40^d14^m399	0.072(2)	11.8	0.880 ± 0.043	10.63 ± 0.03
5MUSES-275	5MUSES_J163751.35+413027.3	16^h37^m514	+41^d30^m273	0.287(1)	25.8	0.131 ± 0.011	12.04 ± 0.04
5MUSES-276	5MUSES_J163751.85+401503.9	16^h37^m519	+40^d15^m040	0.070(2)	8.6	0.771 ± 0.021	10.61 ± 0.03
5MUSES-277	5MUSES_J163802.24+404653.4	16^h38^m022	+40^d46^m534	0.103(2)	9.1	0.204 ± 0.005	10.56 ± 0.06
5MUSES-278	5MUSES_J163805.85+413508.1	16^h38^m059	+41^d35^m082	0.119(2)	10.6	0.573 ± 0.134	11.02 ± 0.03
5MUSES-279	5MUSES_J163808.47+403213.7	16^h38^m085	+40^d32^m138	0.220(2)	11.9	0.486 ± 0.015	11.69 ± 0.05
5MUSES-280	5MUSES_J163809.65+402844.7	16^h38^m096	+40^d28^m448	0.072(2)	17.3	0.696 ± 0.067	10.55 ± 0.04
5MUSES-281	5MUSES_J163906.16+404003.2	16^h39^m062	+40^d40^m033	0.035(1)	6.7	0.719 ± 0.007	9.82 ± 0.03
5MUSES-282	5MUSES_J164019.68+403744.4	16^h40^m197	+40^d37^m444	0.151(1)	10.5	<0.199	10.76 ± 0.08
5MUSES-284	5MUSES_J164043.69+413310.0	16^h40^m437	+41^d33^m100	0.155(2)	5.7	0.720 ± 0.006	11.14 ± 0.04
5MUSES-285	5MUSES_J164046.60+412522.6	16^h40^m466	+41^d25^m226	0.096(2)	20.7	0.098 ± 0.003	10.78 ± 0.05
5MUSES-286	5MUSES_J164101.35+411850.6	16^h41^m014	+41^d18^m507	0.099(2)	22.1	0.072 ± 0.013	10.67 ± 0.05
5MUSES-287	5MUSES_J164115.38+410320.7	16^h41^m154	+41^d03^m207	0.138(2)	5.6	0.519 ± 0.006	11.14 ± 0.02
5MUSES-288	5MUSES_J164135.27+413807.3	16^h41^m353	+41^d38^m073	0.395(2)	5.3	0.072 ± 0.003	11.58 ± 0.07
5MUSES-289	5MUSES_J164153.76+405842.5	16^h41^m538	+40^d58^m426	0.327(2)	5.9	0.119 ± 0.004	11.43 ± 0.03
5MUSES-290	5MUSES_J164211.92+410816.7	16^h42^m119	+41^d08^m168	0.144(2)	11.7	0.546 ± 0.013	11.36 ± 0.04
5MUSES-291	5MUSES_J164214.47+405129.0	16^h42^m145	+40^d51^m290	0.104(2)	14.1	<0.058	10.62 ± 0.01
5MUSES-292	5MUSES_J171033.21+584456.8	17^h10^m332	+58^d44^m567	0.281(2)	6.1	0.325 ± 0.001	11.39 ± 0.07
5MUSES-293	5MUSES_J171124.22+593121.4	17^h11^m242	+59^d31^m215	1.489(2)	5.6	<0.080	12.92 ± 0.02
5MUSES-294	5MUSES_J171232.34+592125.9	17^h12^m324	+59^d21^m262	0.210(2)	8.7	0.507 ± 0.006	11.59 ± 0.04
5MUSES-295	5MUSES_J171233.38+583610.5	17^h12^m334	+58^d36^m103	1.663(1)	5.1	<0.113	13.18 ± 0.04
5MUSES-296	5MUSES_J171233.77+594026.4	17^h12^m337	+59^d40^m268	0.217(2)	5. 1	0.983 ± 0.067	11.29 ± 0.03
5MUSES-297	5MUSES_J171316.50+583234.9	17^h13^m166	+58^d32^m349	0.079(2)	6.7	0.780 ± 0.020	10.34 ± 0.04
5MUSES-298	5MUSES_J171325.18+590531.1	17^h13^m252	+59^d05^m312	0.126(1)	9.4	<0.189	10.33 ± 0.06
5MUSES-299	5MUSES_J171414.81+585221.5	17^h14^m148	+58^d52^m216	0.167(1)	9.0	0.780 ± 0.006	11.19 ± 0.03
5MUSES-300	5MUSES_J171419.98+602724.6	17^h14^m200	+60^d27^m248	2.990(1)	5.6	⋅⋅⋅	13.79 ± 0.09
5MUSES-301	5MUSES_J171430.76+584225.4	17^h14^m308	+58^d42^m254	0.562(2)	8.3	<0.075	11.70 ± 0.06
5MUSES-302	5MUSES_J171446.47+593400.1	17^h14^m464	+59^d33^m598	0.129(1)	7.5	0.637 ± 0.002	11.11 ± 0.02
5MUSES-303	5MUSES_J171447.31+583805.9	17^h14^m473	+58^d38^m058	0.257(2)	5.4	0.836 ± 0.012	11.60 ± 0.04
5MUSES-304	5MUSES_J171513.88+594638.1	17^h15^m138	+59^d46^m383	0.248(1)	5.1	0.338 ± 0.091	11.21 ± 0.04
5MUSES-305	5MUSES_J171544.03+600835.3	17^h15^m440	+60^d08^m352	0.157(2)	6.9	<0.190	10.72 ± 0.04
5MUSES-306	5MUSES_J171550.50+593548.8	17^h15^m505	+59^d35^m487	0.066(2)	9.1	0.073 ± 0.005	10.16 ± 0.04
5MUSES-307	5MUSES_J171614.48+595423.8	17^h16^m145	+59^d54^m236	0.153(2)	8.6	0.827 ± 0.009	11.29 ± 0.03
5MUSES-308	5MUSES_J171630.23+601422.7	17^h16^m302	+60^d14^m227	0.107(1)	8.6	0.833 ± 0.133	10.75 ± 0.05
5MUSES-309	5MUSES_J171650.58+595751.4	17^h16^m506	+59^d57^m520	0.182(1)	6.8	<0.313	10.74 ± 0.10
5MUSES-310	5MUSES_J171711.11+602710.0	17^h17^m111	+60^d27^m100	0.110(1)	9.5	0.488 ± 0.053	10.78 ± 0.06
5MUSES-311	5MUSES_J171747.51+593258.1	17^h17^m475	+59^d32^m581	0.248(2)	5.3	<0.093	10.76 ± 0.12
5MUSES-312	5MUSES_J171754.62+600913.8	17^h17^m546	+60^d09^m134	4.270(1)	9.1	⋅⋅⋅	14.59 ± 0.13
5MUSES-313	5MUSES_J171852.71+591432.0	17^h18^m527	+59^d14^m321	0.322(2)	14.0	0.112 ± 0.010	11.85 ± 0.05
5MUSES-314	5MUSES_J171913.57+584509.1	17^h19^m135	+58^d45^m089	0.318(2)	8.8	<0.243	11.42 ± 0.12
5MUSES-315	5MUSES_J171933.37+592742.8	17^h19^m333	+59^d27^m427	0.139(2)	7.6	0.495 ± 0.005	11.28 ± 0.07
5MUSES-316	5MUSES_J171944.91+595707.7	17^h19^m449	+59^d57^m071	0.069(2)	14.4	0.753 ± 0.005	10.73 ± 0.05
5MUSES-317	5MUSES_J172043.28+584026.6	17^h20^m433	+58^d40^m269	0.125(2)	9.7	0.498 ± 0.006	11.14 ± 0.03
5MUSES-318	5MUSES_J172044.86+582924.0	17^h20^m449	+58^d29^m239	1.697(1)	5.3	<0.094	13.07 ± 0.05
5MUSES-319	5MUSES_J172159.43+595034.3	17^h21^m593	+59^d50^m342	0.028(2)	9.7	0.387 ± 0.031	9.78 ± 0.03
5MUSES-320	5MUSES_J172219.58+594506.9	17^h22^m196	+59^d45^m070	0.272(2)	7.8	<0.133	11.24 ± 0.02
5MUSES-321	5MUSES_J172228.04+601526.0	17^h22^m282	+60^d15^m262	0.742(2)	7.2	<0.111	12.40 ± 0.03
5MUSES-322	5MUSES_J172238.73+585107.0	17^h22^m388	+58^d51^m070	1.624(1)	6.7	<0.062	13.12 ± 0.04
5MUSES-323	5MUSES_J172313.06+590533.1	17^h23^m131	+59^d05^m331	0.108(2)	6.2	0.750 ± 0.037	10.85 ± 0.03
5MUSES-324	5MUSES_J172355.58+601301.7	17^h23^m555	+60^d13^m011	0.175(2)	5.4	0.905 ± 0.034	11.13 ± 0.02
5MUSES-325	5MUSES_J172355.97+594047.6	17^h23^m560	+59^d40^m474	0.030(2)	5.2	0.518 ± 0.098	9.35 ± 0.04
5MUSES-326	5MUSES_J172402.11+600601.4	17^h24^m021	+60^d06^m012	0.156(2)	8.0	0.461 ± 0.024	11.13 ± 0.03
5MUSES-328	5MUSES_J172546.80+593655.3	17^h25^m468	+59^d36^m553	0.035(2)	26.0	0.554 ± 0.041	10.49 ± 0.04
5MUSES-329	5MUSES_J172551.35+601138.9	17^h25^m513	+60^d11^m389	0.029(1)	27.3	0.454 ± 0.005	10.25 ± 0.03
5MUSES-330	5MUSES_J172619.80+601600.1	17^h26^m198	+60^d16^m000	0.924(1)	6.5	<0.039	12.35 ± 0.08

Note. ^aThe redshifts obtained from NASA/IPAC Extragalactic Database are indicated with "1," while the redshifts derived from IRS spectra are indicated with "2."

A machine-readable version of the table is available.

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3.2.3. How Well Can we Constrain IR SED from Mid-IR?

As has been shown above as well as in Kartaltepe et al. (2010), the availability of longer wavelength data greatly reduces the uncertainty in the estimate of L_IR. We need to quantify how well one can constrain the SED of a galaxy if only the continuum shape up to ∼30 μm is available. In Figure 5, we show the comparison of the IRS predicted L^IRS_IR and the L^phot_IR estimated from photometric data points (IRAC 5.8, 8.0 μm and MIPS 24, 70, and 160 μm). For the IRS-only method, we use only the IRS spectrum and do not employ any longer wavelength information (70 and 160 μm fluxes or upper limits) in our SED fitting, with the goal of testing solely the power of using mid-IR SED to predict FIR SED. We find that L_IR estimated from mid-to-FIR photometry are on average 10% higher than L_IR estimated from the IRS-only method, with a considerable scatter of 0.14 dex. It is worth noting that L^IRS_IR deviates from L^phot_IR by more than 0.2 dex for 20% of the sources while 5% of the sources deviate by more than 0.3 dex. We further divide the sources into two groups: cold sources and warm sources, based on the ratio of f_24 μm/f_70 μm. Cold sources (f_24 μm/f_70 μm < 0.2) show an average underestimate of 17% when using the IRS-only method and the 1σ scatter is 0.16 dex, while warm sources (f_24 μm/f_70 μm>0.2) do not show systematic offset in the estimated L_IR from the two methods, with a scatter of 0.18 dex. This comparison suggests that in IR-selected samples, the mid-IR spectrum could be used as an important indicator for L_IR when no longer wavelength data are available. However, for cold sources, the IRS-only method might underestimate L_IR by ∼17%, due to the lack of information on the peak of the SED. For warm sources, although L_IR estimated from the IRS-only method generally agrees with the value estimated from mid-to-far-IR SED, the associated uncertainty is rather large. Thus, for an individual galaxy, the L_IR predicted by its mid-IR SED could be a factor of 1.5 off from its intrinsic value for a significant subset of the population.

**Figure 5.** Ratio of the L_IR derived from using IRAC 5.8, 8.0 and MIPS 24, 70, and 160 μm photometry over L_IR predicted by IRS spectra vs. L_IR. The diamonds represent cold sources with f_24 μm/f_70 μm < 0.2 and the crosses represent the warm sources with f_24 μm/f_70 μm>0.2. The dotted line indicate the median of the luminosity ratios (L_phot/L_IR = 1.10, 1σ = 0.16 dex). The dashed line indicates the median ratio for the cold sources (L_phot/L_IR = 1.17, 1σ = 0.14 dex) and the dot-dashed line indicates the median ratio for the warm sources (L_phot/L_IR = 0.99, 1σ = 0.18 dex).
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3.3. Estimating the Total IR Luminosity from a Single Band

Using Spitzer data, we have obtained accurate estimates of the total infrared luminosities for 5MUSES. In the absence of multi-wavelength data, single-band luminosities have often been used to estimate L_IR (Sajina et al. 2007; Papovich et al. 2007; Pope et al. 2008; Rieke et al. 2009; Bavouzet et al. 2008; Symeonidis et al. 2008). However, the fractional contribution of these photometric bands to the total infrared luminosity varies substantially depending on the dominant energy source. Because the IRS spectrum provides an unambiguous way to identify the energy source for 5MUSES galaxies, our sample is ideal for investigating the difference in the fractional contributions of single-band luminosities to L_IR in different types of objects.

In Figure 6, we plot the ratio of several luminosity bands to L_IR. The PAH luminosities are plotted on the left panel and continuum luminosities are on the right. The dotted, dashed, and dash-dotted lines, respectively, stand for the median ratios for SB, composite, and AGN-dominated sources. Clearly the fractional contribution of a certain band to L_IR is highly dependent on the type of the object, e.g., the monochromatic 24 μm continuum luminosity νL_ν accounts for ∼13% of the total IR luminosity for SB galaxies, while it can contribute on average 30% of L_IR in AGNs. The difference in the ratio of PAH luminosity to L_IR is less significant for different types of objects, because in order to be included on the left panel of this plot, the AGN-dominated sources also need to have a solid detection of PAH feature that could be measured by PAHFIT, i.e., strong AGN sources are excluded. The mean ratios of L_singleband/L_IR are summarized in Table 3. Finally, we also provide our calibration of using single band luminosity to estimate L_IR in the Appendix.

Table 3. Median Luminosity Ratios of the Sample

Luminosity Ratios	SB	Composite	AGN	Whole Sample
log(L_PAH6.2 μm/L_IR)	−2.03 ± 0.13^a	−2.11 ± 0.13	−2.22 ± 0.14	−2.06 ± 0.14
log(L_PAH7.7 μm/L_IR)	−1.51 ± 0.15	−1.54 ± 0.18	−1.76 ± 0.28	−1.53 ± 0.20
log(L_{PAH11.3 μm}/L_IR)	−2.04 ± 0.13	−2.14 ± 0.20	−2.20 ± 0.18	−2.08 ± 0.17
log(L_{PAH6.2+7.7+11.3 μm}/L_IR)	−1.29 ± 0.14	−1.33 ± 0.12	−1.39 ± 0.19	−1.31 ± 0.14
log(L_5.8 μm/L_IR)	−1.44 ± 0.15	−1.36 ± 0.29	−0.77 ± 0.32	−1.33 ± 0.42
log(L_IRAC8 μm/L_IR)	−0.90 ± 0.13	−0.96 ± 0.15	−0.66 ± 0.23	−0.86 ± 0.22
log(L_14 μm/L_IR)	−1.19 ± 0.10	−1.11 ± 0.21	−0.57 ± 0.19	−1.12 ± 0.31
log(L_24 μm/L_IR)	−0.87 ± 0.14	−0.82 ± 0.23	−0.49 ± 0.15	−0.81 ± 0.22

Note. ^aThe dispersion is the 1σ deviation for each group of objects.

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4. AROMATIC FEATURE DIAGNOSTICS

4.1. The Average Spectra

We derive the stacked SEDs for the SB, composite and AGN dominated sources in the 5MUSES sample, combining the low-resolution IRS spectra in the mid-IR with the MIPS photometry at FIR. Although we do not have optical spectroscopy to classify the object types with the Baldwin, Phillips, & Terlevich (BPT) diagram (Baldwin et al. 1981; Kewley et al. 2001), the equivalent widths of PAH features can be used as indicators of star formation activity. The 6.2 and 11.3 μm PAH bands are relatively isolated with little contamination from nearby features, which is important for unambiguously defining the local continuum. However, the 11.3 μm band is located on the shoulder of 9.7 μm silicate feature. Thus, its integrated flux and underlying continuum are likely to be affected by dust extinction effects. As a result, in our discussion, we use the 6.2 μm PAH EWs to classify objects. To be consistent with the studies in the literature, we have adopted the following criteria for our spectral classification: sources with EW > 0.5 μm are SB-dominated; sources with 0.2 < EW ⩽ 0.5 μm are AGN–SB composite and sources with EWs ⩽ 0.2 μm are AGN dominated¹⁸ (Armus et al. 2007). The PAH EWs for the sample are tabulated in Table 2. Out of the 280 sources for which redshifts have been obtained from optical or infrared spectroscopy, there are 123 SB galaxies (44%), 62 composite sources (22%), and 95 AGN-dominated sources (34%).

The 5–30 μm composite spectra are derived by first normalizing individual spectra at rest frame 5.8 μm, and then taking the median in each wavelength bin. In Figure 7(a), we show the typical SED for an SB galaxy in blue and AGNs in red, while the yellow line represents the median SED for SB–AGN composite sources in 5MUSES. The average SEDs have been offset vertically. The shaded regions represent the 16th and 84th percentile of the flux densities at each wavelength.

**Figure 7.** (a) Left panel: the median IRS spectra for SB, composite, and AGN-dominated sources from 5MUSES after normalizing at 5.8 μm. The SEDs have been offset vertically. The shaded regions represent 1σ uncertainties. (b) Right panel: the median SEDs for SB, composite, and AGN sources from mid-IR to FIR, normalized at 5.8 μm.
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The MIPS 70 and 160 μm photometry is crucial for constraining the SED shape of a galaxy and we have also included these data in the final typical SED. Because of the difference in redshift range for sources of different spectral types, we have divided the MIPS 70 and 160 μm data into several rest-wavelength bins before we take the median. For SB and composite sources, we take two bins: 40–70 μm and 70–160 μm. For AGNs, we choose to have three bins due to their larger redshift range: 30–50, 50–100, and 100–160 μm. We take the median flux in each bin and assign the 16th and 84th percentile of the data points in the same bin as the uncertainties. The final median SEDs are presented in Figure 7(b). We can clearly see that besides having much less PAH emission in the mid-IR, the continuum in the AGNs also rises much more slowly than in the SB. The SED of the composite source is between the SB and AGNs and its shape is dependent on how we define a composite source. As can be seen in Figures 7 and 8, our definition of composite sources with 0.2 μm < 6.2 μm PAH EW < 0.5 μm is likely biased toward star formation dominated sources (see Section 4.2).

**Figure 8.** Histogram shows the distribution of the 6.2 μm PAH EW for the 280 known-z sources from the 5MUSES sample. The solid line represents sources which have detection for the 6.2 μm feature, while the dotted line includes upper limits. It is clear that both the solid line and dotted line show a dip in the PAH EW distribution at 0.2–0.3 μm. See the text for the detailed discussion on the bi-modality of the distribution.
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4.2. The Distribution of PAH EWs

With the superb sensitivity and spectral coverage of the IRS, we are able to quantify the strength of the PAH emission over nearly 2 orders of magnitude in its EW. The distribution of the 6.2 μm PAH EWs for the 280 known-redshift galaxies in 5MUSES is shown in Figure 8. The solid line represents the distribution for sources with detection of the 6.2 μm feature, while the dotted line also includes upper limits. We clearly observe a bimodal distribution in Figure 8, with two local peaks at ∼0.1 and ∼0.6 μm. This is somewhat surprising because 5MUSES provides a representative sample completely selected based on IR flux densities and one would have expected a more continuous distribution. Although we still lack redshift information for 50 sources in our sample, the featureless power-law shape of their IRS spectra (except for a few cases where silicate absorption or very weak PAH feature is present) indicate that these are likely to be AGN dominated. Thus if they were included in Figure 8, they would most likely be located in the range between 0 and 0.2 μm, and the bimodal distribution would not be affected. A similar bimodality is also observed in the distribution of the 11.3 μm PAH EWs (not shown here). The observed bimodal distribution of the PAH EWs may be a result of the selection effect for this flux-limited sample: objects at higher redshifts are more likely to be AGNs and thus pile up at the low EW end. However, if we divide our sample into sources with z>0.5 and z < 0.5, the bimodal distribution is again observed in the z < 0.5 population, although all the z>0.5 objects are located at the low EW end. Detailed population modeling is being performed and this issue will be addressed in a later paper.

4.3. PAH Properties versus Mid-IR and FIR Slopes

Another important physical parameter that is often used to quantify the dominant energy source of a galaxy is the ratio of warm to cold dust. It has been shown in previous studies (Desai et al. 2007; Wu et al. 2009) that the 6.2 and 11.3 μm PAH EWs of galaxies are usually suppressed in warmer systems dominated by AGNs, as indicated by the low flux ratios of IRAS f₆₀/f₂₅. For the 5MUSES sample, we have examined the correlation of the 6.2 μm PAH EWs with various continuum slopes, e.g., f₁₅/f_5.8, f₃₀/f_5.8, f₃₀/f₁₅, and f₇₀/f₂₄. The rest-frame continuum fluxes are estimated from the final SED obtained from the fits in Section 3. We find that the continuum ratios of f₃₀/f₁₅ and f₇₀/f₂₄ have the strongest global correlation with the 6.2 μm PAH EWs and the correlation coefficients are both ∼0.7.

In Figures 9(a) and (b), we plot the 6.2 μm PAH EW against f₃₀/f₁₅ and f₇₀/f₂₄. The 5MUSES populations separate into two groups, one with steep spectra and high aromatic content, and the other with slow rising spectra and low aromatic content. The gap between SB and AGN-dominated sources is likely due to the selection effect of this sample. We should note that within each group, there is little if any correlation between the slope and the PAH EW, but it is the contrast between the two groups that gives the overall impression of a correlation. This is consistent with the studies of Veilleux et al. (2009), who have showed the power of using the 7.7 μm PAH EWs and f₃₀/f₁₅ ratios as indicators of AGN activity, despite the large scatter associated with each parameter. To understand the variation in the PAH EWs and continuum slopes, we further divide our sample into smaller bins and estimate the average values in each bin. The sources are divided according to their f₇₀/f₂₄ ratios or f₃₀/f₁₅ ratios and we assign an equal number of objects to each bin. We find that sources in the first three bins with log(f₃₀/f₁₅) >0.65 or log(f₇₀/f₂₄)>0.73 ¹⁹ all have median 6.2 μm PAH EWs of ∼0.60 μm and dispersion of ∼0.2 dex, which again confirms our observation that within the group of starburst galaxies, there is little correlation between the slope and aromatic content. Sources with log(f₃₀/f₁₅) < 0.38 or log(f₇₀/f₂₄) < 0.38 are clearly AGN-dominated with very low PAH EW. The median values and the associated uncertainties of the 6.2 μm PAH EWs and continuum ratios are summarized in Table 4.

**Figure 9.** (a) Left panel: the continuum flux ratio of f_70 μm/f_24 μm vs. the 6.2 μm PAH EW. (b) Right panel: the continuum flux ratio of f_30 μm/f_15 μm vs. the 6.2 μm PAH EWs. The solid line is a fit to all the data points while the dashed line is a fit excluding sources with 6.2 μm PAH EW upper limits. We bin the objects according to their continuum slopes and have equal numbers of objects in each bin. The dotted lines indicate the boundaries of those bins.
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Table 4. Median PAH Strengths and Continuum Ratios of the Sample

log(f₃₀/f₁₅)^a	log(f₇₀/f₂₄)	6.2 μm PAH EW^b	log(L_PAH/L_IR)^c	a	b
>0.898	0.99^+0.08_−0.17	0.57^+0.18_−0.16 (56)^d	−1.40	0.65 ± 0.10	0.94 ± 0.14
0.793–0.898	0.97^+0.11_−0.18	0.62^+0.21_−0.13 (56)	−1.31	0.79 ± 0.33	0.74 ± 0.61
0.650–0.793	1.04^+0.05_−0.35	0.58^+0.17_−0.28 (55)	−1.29	0.70 ± 0.28	0.94 ± 0.65
0.376–0.650	0.57^+0.42_−0.21	0.19^+0.36_−0.09 (55)	−1.54	0.41 ± 0.07	1.72 ± 0.31
<0.376	0.25^+0.21_−0.29	0.08^+0.05_−0.04 (53)	−2.09	0.50 ± 0.03	1.04 ± 0.18

0.76^+0.13_−0.23	>1.053	0.61^+0.15_−0.14 (56)	−1.29	0.62 ± 0.07	0.57 ± 0.10
0.69^+0.18_−0.35	0.954–1.053	0.61^+0.15_−0.14 (56)	−1.31	0.33 ± 0.10	0.99 ± 0.18
0.85^+0.18_−0.42	0.733–0.954	0.60^+0.18_−0.21 (55)	−1.36	0.41 ± 0.02	0.52 ± 0.06
0.61^+0.32_−0.31	0.381–0.733	0.16^+0.25_−0.08 (56)	−1.60	0.47 ± 0.01	0.52 ± 0.06
0.57^+0.31_−0.30	<0.381	0.08^+0.08_−0.03 (52)	−2.07	0.44 ± 0.02	0.23 ± 0.04

Notes. ^aWe sort the spectra by the continuum slope and divide the objects into five groups, in which each group have the same number of sources (56). ^bThe upper limits are also included. ^cThe PAH luminosity is the sum of the 6.2, 7.7, and 11.3 μm PAH luminosities measured from the composite spectra. ^dThe number in the parenthesis indicates the number of objects for which we have measured the 6.2 μm PAH EW or PAH luminosity.

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We also investigate the variation in the ratio of L_PAH/L_IR when the galaxy color indicated by the continuum slope changes. We use the sum of the PAH luminosity from the 6.2 μm, 7.7 μm complex, and 11.3 μm complex to represent L_PAH, measured from the composite spectra derived for each bin. It is clear that the PAH fraction stays nearly constant for starburst-dominated systems, while its contribution drops significantly when AGN becomes more dominant (see Table 4). It has been shown that the PAH luminosity can contribute ∼10% in star-forming galaxies (Smith et al. 2007). For our sample, we find that L_PAH contributes ∼5% to L_IR. This ratio is lower than the SINGS results. We have only taken the 6.2, 7.7, and 11.3 μm bands into account,²⁰ while the SINGS studies include all the PAH emitting bands in the mid-IR. Since the 6.2, 7.7, and 11.3 μm bands account for ∼68% of the power in PAH emission (Smith et al. 2007), our L_PAH/L_IR ratio can be converted to ∼7.5% for the total PAH contribution to L_IR. This is still slightly lower than the SINGS results, but consistent within uncertainties.

Finally, for each group of continuum slope sorted spectra, we derive typical 5–30 μm SEDs by taking the median flux densities in every wavelength bin after normalizing at rest frame 5.8 μm. This will be useful for SED studies when only galaxy colors estimated from broadband photometry are available. These composite SEDs are shown in Figure 10. Then we explore whether the derivation of total IR luminosity from broadband photometry varies with galaxy color. We assume L_IR is correlated with L_24 μm and L_70 μm in the following manner and derive the a and b coefficients in each f₇₀/f₂₄ continuum slope bin (all in rest-frame):

$\begin{equation} \log L_{\mathrm{IR}}=a \log L_{\mathrm{24\;\mu m}}+b \log L_{\mathrm{70\;\mu m}} \end{equation} \tag{ 1 }$

**Figure 10.** (a) Left panel: the typical mid-IR SEDs in each bin of different f_70 μm/f_24 μm ratios. (b) Right panel: the typical SEDs in each bin of different f_30 μm/f_15 μm ratios. All the SEDs have been normalized at 5.8 μm. The colors represent the average spectra derived in each f_70 μm/f_24 μm (or f_30 μm/f_15 μm) color bins listed in Table 4.
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The values of a and b coefficients are summarized in Table 4. To illustrate the variations in each slope bin, we plot the ratio of L_IR/L_24 μm versus L_70 μm/L_24 μm in Figure 11(a). The sources are colored according to their f₇₀/f₂₄ ratios. We clearly observe that when normalized by the monochromatic 24 μm luminosity, L_IR is strongly correlated with L_70 μm and the slopes in each continuum ratio bin become steeper when L_70 μm/L_24 μm increase, except in the last slope bin (see also the b coefficients). We fit a second-order polynomial to the data and find the correlation to be

$\begin{eqnarray} \log \frac{L_{\mathrm{IR}}}{L_{\mathrm{24\;\mu m}}} &=& (0.476\,{\pm}\, 0.005)\,{+}\,(0.509\,{\pm}\, 0.010) \log \frac{L_{\mathrm{70\;\mu m}}}{L_{\mathrm{24\;\mu m}}}\nonumber\\ &&+(0.370\,{\pm}\, 0.022) \left(\log \frac{L_{\mathrm{70\;\mu m}}}{L_{\mathrm{24\;\mu m}}}\right)^2. \end{eqnarray} \tag{ 2 }$

The above equation is derived based on the 5MUSES data. The majority (90%) of the 24 μm luminosities of these 280 galaxies are between 10^9.0 L_☉ and 10^12.0 L_☉. The ratio of f_70 μm/f_24 μm ranges from 0.45 to 34. Our result is consistent with a similar correlation derived by Papovich & Bell (2002), while it diverges for sources with low f_70 μm/f_24 μm ratios, since their modeling work has focused on star-forming galaxies only.

We repeat the same exercise for our sample binned with the f₃₀/f₁₅ ratios. In Figure 11(b), we find that L_IR is correlated with L_30 μm when both quantities are normalized by L_15 μm, although with very large scatter. The dotted line is a linear fit to the data. For a given L_30 μm/L_15 μm ratio, L_IR/L_15 μm can span as much as a factor of 5. The median values in each group binned by the f₃₀/f₁₅ ratios are also summarized in Table 4.

4.4. The Variation in PAH Band-to-Band Strength Ratios

The luminosity ratio of different PAH bands is thought to be a function of the grain size and ionization state (Tielens 2008). In Figure 12, we compare the PAH luminosity ratios of L_PAH7.7 μm/L_{PAH11.3 μm}²¹ with the 6.2 μm PAH EWs for the 5MUSES sample. Only sources with S/N > 3 from PAHFIT measurements for the 7.7 and 11.3 μm bands are included in this plot. We find that the AGN-dominated sources on average have lower L_PAH7.7 μm/L_{PAH11.3 μm} ratios than the composite or SB-dominated sources. The mean log(L_PAH7.7 μm/L_{PAH11.3 μm}) ratios for AGN, composite, and SB galaxies in 5MUSES are 0.32 ± 0.18, 0.53 ± 0.15 and 0.53 ± 0.08, respectively. This is consistent with the studies on the nuclear spectra of low luminosity star-forming galaxies from SINGS (Smith et al. 2007), which also show decreased L_PAH7.7 μm/L_{PAH11.3 μm} ratios in spectra with AGN signals. Smith et al. (2007) suggest that this change in the ratio of L_PAH7.7 μm/L_{PAH11.3 μm} is likely due to the destruction of the smallest PAHs by hard photons from the AGN. On the other hand, AGN are less extinguished than SB or composite sources, thus if PAHFIT underestimates the extinction correction, it will preferentially underestimate the 11.3 μm fluxes more than the 7.7 μm feature in SB/Composite sources, thus resulting in the elevated ratios of L_PAH7.7 μm/L_{PAH11.3 μm} in SB/composite systems.

In Figure 13(a), we show the histogram of the L_PAH7.7 μm/L_{PAH11.3 μm} ratios for the SB-dominated sources in 5MUSES. We have overplotted the values from the SINGS sample. To make a fair comparison, we remeasure the PAH luminosity and EWs for the SINGS nuclear spectra using the same method as 5MUSES and classify the sources with 6.2 μm PAH EWs larger than 0.5 μm as SB-dominated. We have also included the distribution of the L_PAH7.7 μm/L_{PAH11.3 μm} ratios from the UV/SDSS selected star-forming galaxies sample of SSGSS (O'Dowd et al. 2009). For this last sample, the star-forming galaxies are classified from optical spectroscopy using the BPT diagram method (Baldwin et al. 1981; Kewley et al. 2001). We find that the distribution for SB galaxies in 5MUSES and SSGSS is similar, while both samples appear to have lower L_PAH7.7 μm/L_{PAH11.3 μm} ratios than the nuclear spectra of SINGS SB galaxies. The mean log(L_PAH7.7 μm/L_{PAH11.3 μm}) ratio for SINGS starbursts is 0.63 ± 0.06 while it is 0.53 ± 0.08 for 5MUSES starbursts. This might be a resolution effect: if the physical conditions at the nuclear region of a galaxy indeed modifies the distribution of the L_PAH7.7 μm/L_{PAH11.3 μm} ratios, it might be visible only in the spectra taken through apertures with small projected sizes. The median redshift for the SB-dominated sources in the 5MUSES sample is 0.12, while the median redshift for the SSGSS sample is 0.08. At the redshift of 0.08, 1'' corresponds to 1.53 kpc. The IRS spectra (for SL, the slit width is ∼3 farcs 6) of 5MUSES and SSGSS sources are integrated from the whole galaxy, thus diluting the signature of the nuclear regions. Smith et al. (2007) have shown the changes in the L_PAH7.7 μm/L_{PAH11.3 μm} ratios in spectra extracted from bigger to smaller apertures in two star-forming galaxies: the L_PAH7.7 μm/L_{PAH11.3 μm} ratios measured from star-forming galaxy spectra extracted with smaller apertures are higher than those measured from larger apertures, consistent with our results. More recently, Pereira-Santaella et al. (2010) have suggested that the 11.3 μm PAH feature is more extended than the 6.2 or 7.7 μm PAH from a spatially resolved mapping study of local luminous infrared galaxies. They have observed lower L_PAH6.2 μm/L_{PAH11.3 μm} ratios in the nucleus consistent with our results. We also show the distribution of L_PAH6.2 μm/L_PAH7.7 μm ratios in Figure 13(b). No significant difference has been observed between the 5MUSES, SINGS, and SSGSS samples.

Finally in Figure 14, we present the variation in PAH band-to-band ratios for the three strongest bands at 6.2, 7.7, and 11.3 μm of the 5MUSES sample. Only sources with S/N > 3 from PAHFIT measurements for all three PAH bands are included in this figure. The two dark lines represent the traces for fully neutral or fully ionized PAH molecules with different numbers of carbon atoms predicted from modeling work (Draine & Li 2001). The L_PAH7.7 μm/L_{PAH11.3 μm} ratios span a range of a factor of 5 while the L_PAH6.2 μm/L_PAH7.7 μm ratios only vary by a factor of 2. The uncertainty in the L_PAH7.7 μm/L_{PAH11.3 μm} ratios is 0.09 dex and it is 0.05 dex for the L_PAH6.2 μm/L_PAH7.7 μm ratios. This narrow range of L_PAH6.2 μm/L_PAH7.7 μm ratios is consistent with the values for the SINGS nuclear sample (Smith et al. 2007), while we have not observed any sources with extremely low L_PAH6.2 μm/L_PAH7.7 μm ratios (<0.2) as has been found in the SSGSS sample (O'Dowd et al. 2009).

4.5. PAH Band Ratio versus [Ne iii]/[Ne ii]

Because of the large difference in ionization potentials of the Ne⁺⁺ (41 eV) and Ne⁺ (21.6 eV) ions, the ratio of [Ne iii]/[Ne ii] is often used as a tracer of the hardness of the radiation field. The [Ne iii] 15.55 μm and [Ne ii] 12.81 μm lines are among the strongest lines emitted in the mid-IR and because differential extinction effects between their wavelengths are small, they are particularly valuable. We use the IRS low-res spectra to identify and measure these lines.²² The line fluxes measured from low-resolution spectra have on average an uncertainty of ∼20%.

In Figure 15, we show the flux ratios of L_PAH7.7 μm/L_{PAH11.3 μm} versus [Ne iii]/[Ne ii]. The solid symbols denote detections while the open triangles represent upper/lower limits. We overplot the median L_PAH7.7 μm/L_{PAH11.3 μm} for SB-dominated sources in 5MUSES as the dotted line. We find that the SB, composite and AGN-dominated sources (including sources with upper/lower limits) are almost evenly distributed on the two sides of the dotted line. However, the AGNs with solid detections on both axes do appear to have lower L_PAH7.7 μm/L_{PAH11.3 μm} ratios in general. As has been discussed in Section 4.4, this is consistent with the studies of Smith et al. (2007) using the SINGS nuclear spectra. We note that the 5MUSES sample does not have sources with extreme L_PAH7.7 μm/L_{PAH11.3 μm} ratios comparable to the lowest ones reached by SINGS. This is probably because the SINGS spectra probe smaller, more central and thus more AGN-dominated regions. It should also be noted that the AGN luminosities in 5MUSES are substantially higher than SINGS. Our results are consistent with O'Dowd et al. (2009), who have studied a UV–SDSS selected sample at z ∼ 0.1 and do not observe extreme L_PAH7.7 μm/L_{PAH11.3 μm} ratios either. We also note that the range of [Ne iii]/[Ne ii] ratios is similar for all three groups of objects that we have classified based on their 6.2 μm PAH EWs. This is consistent with the study of Bernard-Salas et al. (2009), who found no correlation between the PAH EWs and the [Ne iii]/[Ne ii] ratios in a sample of starburst galaxies. However, in more extreme radiation field conditions, such as low-metallicity environments, PAH EWs have been observed to anti-correlate with the radiation field hardness indicated by [Ne iii]/[Ne ii] ratios (Wu et al. 2006).

5. CONCLUSIONS

We have studied a flux-limited ( $f_{24\rm \;\mu m}>5$ mJy) representative sample of 330 galaxies surveyed with the IRS on board the Spitzer Space Telescope. Secure redshifts of 280 objects have been obtained from optical or infrared spectroscopy. The redshifts of the 5MUSES sample ranges from 0.08 to 4.27, with a median value of 0.144. This places the 5MUSES sample at intermediate redshift, which bridges the gap between the nearby bright sources known from previous studies and the z ∼ 2 objects pursued in most of the IRS follow-up observations of deep 24 μm surveys. The simple selection criteria ensure that our sample provides a complete census of galaxies with crucial information on understanding the galaxy evolution processes.

Using mid-IR spectroscopy and mid-to-far IR photometry, we have obtained accurate estimates on the total infrared luminosities of 5MUSES galaxies. This is achieved by minimizing the χ² to find the best-fit template from our newly constructed empirical SED library built upon recent Spitzer observations. The availability of longer wavelength data also greatly reduces the uncertainties in L_IR. When only one IRS spectrum is available, one can still predict the shape of the FIR SED from the mid-IR and estimate L_IR, albeit with substantially larger uncertainties (0.2 dex). The IRS-only method does not introduce a systematic bias when estimating L_IR for warm sources, but could underestimate the L_IR by ∼17% for cold sources, due to the lack of information sampling the peak of the SED. The fractional contribution of single-band luminosity to L_IR varies depending on the dominant energy source and the average values have been calculated for the SB, composite, and AGN-dominated sources, as well as the whole sample.

We analyze the properties of the PAH emission in our sample using the IRS spectra. The PAH EWs show a bimodal distribution, which might be related to the selection effect of the sample. The starburst and AGN-dominated sources form two clumps when comparing the continuum slopes and PAH EWs, while there is little discernible correlation within each group. Average spectra binned with the 6.2 μm PAH EWs, the continuum slopes of log(f₃₀/f₁₅) and log(f₇₀/f₂₄) have been derived to show the typical SED shapes. The variation in PAH EW and L_PAH/L_IR ratios when galaxy color changes have also been inspected. The galaxy color provides essential constraint on estimating the total infrared luminosity from broadband photometry.

We have also inspected the band-to-band PAH intensity ratios with regard to different spectral types. The L_PAH7.7 μm/L_{PAH11.3 μm} ratios in AGN-dominated sources in 5MUSES are on average lower than the SB or composite sources. The SB, composite, and AGN-dominated sources have mean log(L_PAH7.7 μm/L_{PAH11.3 μm}) ratios of 0.53 ± 0.08, 0.54 ± 0.15 and 0.32 ± 0.18, respectively. The mean log(L_PAH7.7 μm/L_{PAH11.3 μm}) ratio for the SB-dominated sources in 5MUSES is lower than the mean ratio derived from the nuclear spectra of SB galaxies in SINGS (0.63 ± 0.06), which might indicate a difference in the physical conditions near the nucleus versus over the entire galaxy. At the median redshift of our sample, the IRS SL slit width corresponds to a few kpc, thus even if the ionization state or grain size distribution is different at the nuclear level, the signal might get diluted when we study the integrated spectrum and would result in the different log(L_PAH7.7 μm/L_{PAH11.3 μm}) ratio distribution.

Finally, we provide our calibration of using PAH luminosity or mid-IR continuum luminosity to estimate L_IR in the Appendix. We have shown that single-band luminosities trace the L_IR differently in SB or AGN-dominated sources and we provide calibrations for each object type. This technique will be useful for luminosity estimates when no multi-wavelength data are available.

We thank the anonymous referee whose comments have helped to improve this paper. This work was based on observations made with the Spitzer Space Telescope, which is operated by JPL/Caltech under a contract with NASA. The observations are associated with the Spitzer Legacy Program 40539. The authors acknowledge support by NASA through awards issued by JPL/Caltech. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

APPENDIX: ESTIMATING THE TOTAL INFRARED LUMINOSITY FROM PAH OR MONOCHROMATIC CONTINUUM LUMINOSITIES

In Section 3, we have discussed in detail our method to estimate the total infrared luminosities for the 5MUSES sources. The empirical library of SED templates built from Spitzer observations, as well as the availability of photometric and spectroscopic data from mid-IR to FIR for 5MUSES, allows us to have precise estimates on their L_IR. We have shown in Figure 5 the importance of having FIR data in determining the total energy output in the infrared. However, for high redshift galaxies, FIR observations are not always available. Herschel Space Observatory will provide FIR measurements from 70 to 500 μm to reveal the properties of cold dust in many systems. For now, we provide our calibration of estimating L_IR from several bands in the mid-IR and discuss its applications. The following correlations are derived by performing a linear fit to the 5MUSES data with equal weight on each object because the dispersion of the data point in the x–y plane is larger than the measurement errors.

As has been shown in many studies, the infrared SED of a starburst galaxy is drastically different from that of an AGN (Brandl et al. 2006; Hao et al. 2007; Armus et al. 2007). Because of these substantial variations in the SED shapes, it is crucial to calibrate the luminosity estimates for each spectral type. Here, we provide our luminosity calibrations based on the three spectral types: starburst, composite, and AGN. The following PAH luminosities are derived from the PAHFIT method.

1.
6.2 μm PAH: with a wavelength cut at 28 μm for the James Webb Space Telescope (JWST), the 6.2 μm PAH feature might be the only PAH band that could be observed to quantify star formation activities in z ∼ 3 sources when JWST is launched.For SB sources:
$\begin{equation} \log L_{\mathrm{IR}}=(2.40\,{\pm}\, 0.22)\,{+}\,(0.96\,{\pm}\, 0.03)\log L_{\mathrm{PAH6.2\;\mu m}}. \end{equation} \tag{ A1 }$
For composite sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.76\,{\pm}\, 0.32)\,{+}\,(1.04\,{\pm}\, 0.04)\log L_{\mathrm{PAH6.2\;\mu m}}. \end{equation} \tag{ A2 }$
For AGN sources:
$\begin{equation} \log L_{\mathrm{IR}}=(-0.58\,{\pm}\, 0.58)\,{+}\,(1.30\,{\pm}\, 0.06)\log L_{\mathrm{PAH6.2\;\mu m}}. \end{equation} \tag{ A3 }$
2.
7.7 μm PAH: the 7.7 μm PAH complex is the strongest band among the various PAH features. It is often used to estimate the total infrared luminosities for the z ∼ 1–2 sources pursued in IRS observations of 24 μm selected sources.For SB sources:
$\begin{equation} \log L_{\mathrm{IR}}=(2.30\,{\pm}\, 0.26)\,{+}\,(0.91\,{\pm}\, 0.003)\log L_{\mathrm{PAH7.7\;\mu m}}. \end{equation} \tag{ A4 }$
For composite sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.80\,{\pm}\, 0.44)\,{+}\,(0.98\,{\pm}\, 0.05)\log L_{\mathrm{PAH7.7\;\mu m}}. \end{equation} \tag{ A5 }$
For AGN sources:
$\begin{equation} \log L_{\mathrm{IR}}=(3.45\,{\pm}\, 0.90)\,{+}\,(0.83\,{\pm}\, 0.09)\log L_{\mathrm{PAH7.7\;\mu m}}. \end{equation} \tag{ A6 }$
3.
11.3 μm PAH: the 11.3 μm band is another strong PAH band in the mid-IR that is relatively isolated from other PAH bands. However, the integrated fluxes from this band might be affected by the 9.7 μm silicate feature.For SB sources:
$\begin{equation} \log L_{\mathrm{IR}}=(2.18\,{\pm}\, 0.22)\,{+}\,(0.98\,{\pm}\, 0.03)\log L_{\mathrm{PAH11.3\;\mu m}}. \end{equation} \tag{ A7 }$
For composite sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.49\,{\pm}\, 0.43)\,{+}\,(1.07\,{\pm}\, 0.05)\log L_{\mathrm{PAH11.3\;\mu m}}. \end{equation} \tag{ A8 }$
For AGN sources:
$\begin{equation} \log L_{\mathrm{IR}}=(2.22\,{\pm}\, 0.36)\,{+}\,(1.00\,{\pm}\, 0.04)\log L_{\mathrm{PAH11.3\;\mu m}}. \end{equation} \tag{ A9 }$
4.
6.2+7.7+11.3 μm PAH: in normal star-forming galaxies, the PAH emission accounts for ∼10%–15% of the total infrared luminosities (Smith et al. 2007), while this fraction is smaller for local ULIRGs (Armus et al. 2007). Here we use the sum of the three strongest PAH bands, the 6.2, 7.7, and 11.3 μm PAH luminosities to represent the total PAH luminosities. However, when using the correlation provided here, one needs to keep in mind that the properties of PAHs studied in the local universe might be different at high z, as has already been revealed in the study of several z ∼ 2 luminous infrared galaxies (Sajina et al. 2007; Pope et al. 2008). Understanding the PAH contribution in our intermediate-redshift sample would also be instrumental for tackling the problem of whether and how PAH emission evolves with redshift in future studies.For SB sources:
$\begin{eqnarray} \log L_{\mathrm{IR}}&=& (1.82\,{\pm}\, 0.25)\,{+}\,(0.95\,{\pm}\, 0.03)\nonumber\\ &&\times\log L_{\mathrm{PAH6.2+7.7+11.3\;\mu m}}. \end{eqnarray} \tag{ A10 }$
For composite sources:
$\begin{eqnarray} \log L_{\mathrm{IR}}&=&(0.73\,{\pm}\, 0.36)\,{+}\,(1.06\,{\pm}\, 0.04)\nonumber\\ &&\times\log L_{\mathrm{PAH6.2+7.7+11.3\;\mu m}}. \end{eqnarray} \tag{ A11 }$
For AGN sources:
$\begin{eqnarray} \log L_{\mathrm{IR}}&=& (-2.13\,{\pm}\, 1.01)\,{+}\,(1.35\,{\pm}\, 0.10)\nonumber\\ &&\times\log L_{\mathrm{PAH6.2+7.7+11.3\;\mu m}}. \end{eqnarray} \tag{ A12 }$
5.
5.8 μm monochromatic continuum luminosity: the 5.8 μm continuum luminosity provides a crude estimate of L_IR. In AGN-dominated sources, the 5.8 μm continuum will be elevated due to the presence of very hot dust component. This is also a band that is available for most of the high-redshift samples observed by Spitzer, and for JWST when it is launched.For SB sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.94\,{\pm}\, 0.25)\,{+}\,(0.95\,{\pm}\, 0.03)\log L_{\mathrm{5.8\;\mu m}}. \end{equation} \tag{ A13 }$
For composite sources:
$\begin{equation} \log L_{\mathrm{IR}}=(2.68\,{\pm}\, 0.45)\,{+}\,(0.87\,{\pm}\, 0.05)\log L_{\mathrm{5.8\;\mu m}}. \end{equation} \tag{ A14 }$
For AGN sources:
$\begin{equation} \log L_{\mathrm{IR}}=(2.34\,{\pm}\, 0.29)\,{+}\,(0.85\,{\pm}\, 0.03)\log L_{\mathrm{5.8\;\mu m}}. \end{equation} \tag{ A15 }$
6.
IRAC 8 μm: the rest-frame IRAC 8.0 μm band has included both dust continuum emission and PAH emission from the 7.7, 8.3, and 8.6 μm PAH band (if present). It provides a useful channel for estimating L_IR from PAH features when no spectroscopy is available.For SB sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.60\,{\pm}\, 0.21)\,{+}\,(0.93\,{\pm}\, 0.02)\log L_{\mathrm{IRAC 8\;\mu m}}. \end{equation} \tag{ A16 }$
For composite sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.45\,{\pm}\, 0.26)\,{+}\,(0.95\,{\pm}\, 0.03)\log L_{\mathrm{IRAC 8\;\mu m}}. \end{equation} \tag{ A17 }$
For AGN sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.70\,{\pm}\, 0.26)\,{+}\,(0.90\,{\pm}\, 0.02)\log L_{\mathrm{IRAC 8\;\mu m}}. \end{equation} \tag{ A18 }$
7.
14 μm monochromatic continuum luminosity: the 14 μm is an important band in the mid-IR that is still sensitive to the AGN emission.For SB sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.44\,{\pm}\, 0.16)\,{+}\,(0.97\,{\pm}\, 0.02)\log L_{\mathrm{14\;\mu m}}. \end{equation} \tag{ A19 }$
For composite sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.76\,{\pm}\, 0.37)\,{+}\,(0.93\,{\pm}\, 0.04)\log L_{\mathrm{14\;\mu m}}. \end{equation} \tag{ A20 }$
For AGN sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.62\,{\pm}\, 0.29)\,{+}\,(0.90\,{\pm}\, 0.03)\log L_{\mathrm{14\;\mu m}}. \end{equation} \tag{ A21 }$
8.
24 μm monochromatic continuum luminosity: here, we refer to the 24 μm continuum luminosity averaged in 1 μm range, instead of the rest-frame MIPS 24 μm band. This is because if we use the MIPS 24 μm band, sources at z > ∼ 0.3 will be eliminated from this study due to the limited wavelength coverage of its rest-frame mid-IR spectra. The sources we use in the calibration mostly have 10¹⁰ L_☉ < L_IR < 10¹² L_☉ and no quasars have been included in this calibration because of the wavelength cut. Since our sample is selected at 24 μm, it tends to favor warmer sources, which also needs to be kept in mind when using these relations.For SB sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.56\,{\pm}\, 0.23)\,{+}\,(0.93\,{\pm}\, 0.02)\log L_{\mathrm{24\;\mu m}}. \end{equation} \tag{ A22 }$
For composite sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.64\,{\pm}\, 0.44)\,{+}\,(0.91\,{\pm}\, 0.04)\log L_{\mathrm{24\;\mu m}}. \end{equation} \tag{ A23 }$
For AGN sources:
$\begin{equation} \log L_{\mathrm{IR}}=(1.67\,{\pm}\, 0.47)\,{+}\,(0.89\,{\pm}\, 0.05)\log L_{\mathrm{24\;\mu m}}. \end{equation} \tag{ A24 }$