CLASSY V: The impact of aperture effects on the inferred nebular properties of local star-forming galaxies

Strong nebular emission lines are an important diagnostic tool for tracing the evolution of star-forming galaxies across cosmic time. However, different observational setups can affect these lines, and the derivation of the physical nebular properties. We analyze 12 local star-forming galaxies from the COS Legacy Spectroscopy SurveY (CLASSY) to assess the impact of using different aperture combinations on the determination of the physical conditions and gas-phase metallicity. We compare optical spectra observed with the SDSS aperture, which has a 3"of diameter similar to COS, to IFU and longslit spectra, including new LBT/MODS observations of five CLASSY galaxies. We calculate the reddening, electron densities and temperatures, metallicities, star formation rates, and equivalent widths (EWs). We find that measurements of the electron densities and temperatures, and metallicity remained roughly constant with aperture size, indicating that the gas conditions are relatively uniform for this sample. However, using the IFU observations of 3 galaxies, we find that the E(B-V) values derived from the Balmer ratios decrease ( by up to 53%) with increasing aperture size. The values change most significantly in the center of the galaxies, and level out near the COS aperture diameter of 2.5". We examine the relative contributions from the gas and stars using the H$\alpha$ and [OIII] $\lambda$5007 EWs as a function of aperture light fraction, but find little to no variations within a given galaxy. These results imply that the optical spectra provide nebular properties appropriate for the FUV CLASSY spectra, even when narrow 1.0"long-slit observations are used.


INTRODUCTION
A key goal of galaxy evolution is to understand the main processes shaping the stellar and nebular gas content of galaxies across cosmic time. In the coming years, the new generation of space and ground-based telescopes, such as the James Web Space Telescope (JWST) and the Extremely Large Telescopes (ELTs) will provide our the first probes of the physical conditions in the first galaxies. In this context, the study of nearby, chemically-young, high-ionization dwarf galaxies provide a more detailed view of conditions similar to these high-z systems (e.g., Senchyna et al. 2017;Berg et al. 2021), and, thus, help to constrain and interpret their physical properties. In particular, optical emission spectra of local, star-forming, dwarf galaxies provide a rich source of information about the physical properties of their interstellar medium (ISM), such as dust content, electron density and temperature structure, gas-phase metallicity, and the ionization state of the gas (e.g., Lequeux et al. 1979;Campbell et al. 1986;Skillman et al. 1989;Pagel et al. 1992;Vilchez 1995;Izotov & Thuan 1999;Kunth & Östlin 2000;Berg et al. 2012;Berg et al. 2016;Sánchez Almeida et al. 2016;Guseva et al. 2017;James et al. 2017;Berg et al. 2019;McQuinn et al. 2020; and many more).
Recently, Berg et al. (2022; hereafter, Paper I) presented the COS Legacy Archive Spectroscopic SurveY (CLASSY) treasury, obtained with Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST). CLASSY comprises a sample of 45 local (0.002 < z < 0.182) star-forming galaxies with high-resolution (R ∼ 15, 000) far-ultraviolet (FUV) COS spectra and moderate-resolution (R ∼ 2, 000) optical spectra. Most of the optical observations are archival spectra from the Sloan Digital Sky Survey Data Release 12 (SDSS) (Eisenstein et al. 2011), but is complimented by long-slit and integral field unit spectroscopy (IFU) spectroscopy for some CLASSY galaxies (e.g., ESO 096.B-0923; PI Östlin, ESO 0103.B-0531; PI Erb and Senchyna et al. (2019); Sanders et al. (2022)). The CLASSY sample covers a broad range of physical properties such as reddening (0.02 < E(B − V ) < 0.67), nebular density, (10 < n e (cm −3 ) < 1120), gas-phase metallicity (7.0 < 12+log(O/H) < 8.7), ionization parameter (0.5 < [O III] λ5007/[O II] λ3727 < 38.0), stellar mass (6.2 < log M (M ) < 10.1), and star formation rate (−2.0 < log SFR (M yr −1 ) < +1.6). One of the main purposes of CLASSY is to create a database of local star-forming galaxies to study and interpret the physical properties of the stel-lar and gas-phase content of star-forming galaxies across all redshifts. However, in contrast to distant galaxies, a large fraction of the light of these very nearby objects can fall out of the aperture of the fiber or slit used, resulting in aperture effect issues.
While optical spectra of individual H II regions in nearby galaxies have provided the foundation for diagnosing the physical conditions in nebular gas, it is not yet clear whether the same diagnostics are appropriate for the integrated-light spectra observed from distant galaxies (e.g., Kobulnicky et al. 1999;Moustakas & Kennicutt 2006). Several studies have focused their attention on the combined impact of aperture size with different galaxy morphologies on the inferred physical properties of local and high-redshift galaxies (e.g, Zaritsky et al. 1995;Pérez-González et al. 2003;Gómez et al. 2003;Hopkins et al. 2003;Brinchmann et al. 2004;Kewley et al. 2005). For example, Kewley et al. (2005) presented an analysis of the aperture effects on the computation of SFR, reddening (E(B −V )), and gas-phase metallicity for different Hubble-type galaxies. These authors concluded that apertures capturing < 20% of the total galaxy's light show significant differences in the determination of the global galaxy properties. Therefore, aperture effects can strongly bias comparisons among different surveys Kewley et al. (2005). As such, aperture corrections are fundamental for small apertures to avoid biases (Hopkins et al. 2003;Nakamura et al. 2004;Brinchmann et al. 2004).
Recently, Mannucci et al. (2021) analyzed the impact of the different aperture sizes (e.g., representative apertures for long-slit and IFU spectroscopy) from pc to kpc scales in nearby galaxies. These authors found significant differences in the flux ratios involving low-ionization emission lines (i.e., [S II] λλ6717,6731/Hβ) mainly due to the internal structure of H II regions. While we cannot resolve individual H II regions in most dwarf star-forming galaxies, aperture effects may still play an important role when different instruments/apertures sample different physical sizes of the same galaxy. Therefore, aperture effects can lead to significant biases that affect the computation of physical properties in both local star-forming galaxies and high redshift galaxies (Kewley et al. 2005;Pérez-González et al. 2003;Gómez et al. 2003;Brinchmann et al. 2004). For this reason, it is important to understand and characterize the effects of aperture size on the interpretation of galaxy properties derived from rest-frame optical spectra.
In this paper, we present an analysis of the 12 CLASSY galaxies for which multiple optical spectra exist with different apertures. The variations in spatial scales probed by these different spectra provide an ideal laboratory to assess the variations of physical properties. Therefore, this sample provides an excellent opportunity to assess whether differences in aperture size or instrument produce significantly different, optically-derived properties. In the local Universe, optical emission lines are the main source of information to obtain reliable measurements of the gas-phase metallicity, the ionization state of the gas, star formation rate, and other valuable nebular properties. However, the study of FUV spectra is crucial to fully characterize the young stellar populations and their impact of the nebular properties. Therefore, a deeper understanding of galaxy evolution requires a joint analysis of the FUV+optical CLASSY spectra. Given the different instruments and apertures used for the CLASSY FUV+optical spectra, it is important to evaluate the potential bias introduced by such observations. With our sub-sample of 12 CLASSY star-forming galaxies, we investigate the effect of aperture sizes on optical spectra derived nebular properties. Further, this analysis is crucial to determine whether our optically-derived nebular properties are appropriate for the 2. 5-diameter aperture of the HST/COS spectra.
The structure of this paper is as follows. We describe our sample and the optical observation in Section 2. In Section 3, we present the analysis of observations, the computation of the reddening, and aperture comparison. In Sections 4, we calculate physical conditions, metallicities and equivalent widths (EWs), and the ionization parameter of the gas for the multiple apertures. In Section 5, we compare and discuss the results and finish with a summary and conclusion in Section 6.

OPTICAL SPECTRA
The ancillary optical spectra of CLASSY comprises observations of APO/SDSS (Eisenstein et al. 2011) of 38 out of 45 objects, and multiple observations of Keck/ESI and VLT/MUSE IFU (Sanders et al. 2022;Senchyna et al. 2019) for a small sub-sample of the CLASSY galaxies ). In addition, seven CLASSY galaxies were observed using long-slit spectroscopy with the Large Binocular Telescope (LBT) (Hill et al. 2010) to ensure the accurate measurement of the physical properties of these galaxies (see Section 2.1). In summary, the CLASSY sample is fully covered by optical spectra for different observational sets available James et al. 2021) and follow-up observations. The telescope and instruments used for the optical observations in this paper are listed in Table 1.
In this work, we have selected the 12 star-forming galaxies from the CLASSY sample having optical spectra with multiple aperture sizes (1.0 -3.0 ), observational modes (long-slit and IFU model), and spectral resolutions. In particular, the IFU data allow us to map the gas emission using different aperture sizes, which provides a better comparison between the different observations of this sample, e.g., to analyze the results obtained using the same aperture as in HST/COS James et al. 2021).
In Figure 1, we show the optical images of Pan-STARRS 1 in the r-band for the 12 galaxies of this study. We also overlay the aperture at the observed position angle. SDSS and MUSE observations are indicated with circular apertures of 3 and 2.5 of diameter, respectively. ESI and LBT apertures have an size of 1 wide with an 1D extraction box of ∼ 1 × 2 and 1 × 2.5 respectively. In Fig. 1, we show the extraction sampling for each aperture. Although most of the galaxies show extended emission, the multiple aperture are covering the bright emission region of each galaxy.
To identify and compare the different aperture observations, we simply refer to the observations as SDSS, LBT, MUSE and ESI for the rest of the paper.

LBT/MODS Observations
Here we present new optical spectra for seven CLASSY galaxies using the Multi-Object Double Spectographs (MODS, Pogge et al. 2010) mounted on the LBT (Hill et al. 2010). The LBT spectra of two of these galaxies (J1044+0353 and J1418+2102) was already reported in Berg et al. (2021). The optical LBT/MODS spectra of the remaining five CLASSY galaxies were obtained on the UT dates of Feb 11th-12th and March 17th-18th, 2021, respectively. MODS has a large wavelength coverage from 3200 Å to 10000 Å with a moderate spectral resolution of R ∼ 2000. The blue and red spectra were obtained simultaneously using the G400L (400 lines mm −1 ) at R ≈ 1850 and G670L (250 lines mm −1 ) at R ≈ 2300 gratings. The slit length was 60 arcsec with a width of 1 arcsec. To minimize flux losses due to atmospheric differential refraction (Filippenko 1982), the slit was oriented along the parallactic angle at half the total integration at airmasses ranging between 1.05 and 1.31. Each object was observed with a total exposure time of 45 min (3×900s exposures). Fig. 1 shows the slit position and orientation of the LBT/MODS observations for J0808+3948, J0944-0038, J1148+2546 (SB 182), J1323-0132 and J1545+0858 (1725-54266-068). For comparison purposes, the LBT/MODS slit has been truncated (1 × 2.5 ) to show the extraction region of the observation. The slit was centered on the highest surface brightness knots of optical emission based on SDSS r-band images, following the position of HST/COS aperture of each CLASSY galaxy in the UV   Figure 1. Field of View -optical images of Pan-STARRS in r-band for 12 star-forming galaxies of CLASSY. The 3 SDSS aperture used for the optical spectra is shown as a cyan circle and the 2.5 MUSE aperture as a magenta circle, whose diameter and pointing is the same as the HST/COS 2.5 aperture. We highlight for a comparison also the 1 × 2.5 LBT/MODS slit (green box) and 1 × 2 Keck/ESI slit (orange box). The position of the apertures is centred at the brightest emission knot of each galaxy using SDSS r-images. The labels show the ID of each galaxy used in this study and the alternative name for some objects. North up and East to the left.
We use the CHAOS project's data reduction pipeline (Berg et al. 2015;Croxall et al. 2016;Rogers et al. 2021) to reduce LBT/MODS observations. To correct for bias and flat field we apply the modsCCDRed 2 Python programs to the standard stars, science objects and calibration lamps. The resulting CCD images are used in the beta version of the MODS reduction pipeline 3 which runs within the XIDL 4 reduction package. We perform sky subtraction, wavelength calibration and flux calibration using the standard stars Feige 34, Feige 67 and G191-B2B. In Fig. 2, we show the one-dimensional spectra for these galaxies. We have labeled the main emission line features. Note that with the exception of J0808+3948, the rest of the galaxies shows the very high ionization emission line He II λ4686   Berg et al. (2022) provide a detailed description of the optical observations for CLASSY, while the scaling of the optical data to UV data is presented in Mingozzi et al. (2022). Here, we give a brief summary of the main characteristics of the CLASSY galaxies relevant for this study. In Table 1, we list the optical observations of the selected galaxies. It includes the identification of the galaxy that we use in this work, the alternative names used in the literature, the coordinates, the observational ancillary, aperture size extraction of the observations and the optical size of each galaxy represented as the total galaxy radius, (∼ R 100 /2) (see Sec. 5.1).
APO/SDSS: SDSS sample comprises 12 observations of 3 fiber diameter with a range in wavelength of 3800-9200 Å and spectral resolution of R ≈ 1500 − 2500 (Eisenstein et al. 2011). This wavelength range allows to measure the main emission lines necessary for the analysis of the physical properties of these galaxies. We use this sample as reference to compare with the rest of the observations since the aperture size and center are similar to those of HST/COS data   Figure 2. New optical LBT/MODS spectra of five CLASSY galaxies. The dotted lines indicate the main emission lines used in this study. F λ is units of 10 −16 ergs −1 s −1 cm −2 Å −1 . We added an offset vertically for display with exception of J1545+0858. The offset corresponds to 4, 8, 12, 14 for J1323-0132, J1148+2546, J0944-0038 and J0808+3948, respectively. The emission lines for these spectra used in this study are reported in Table 3, and the complete version of all emission lines of MODS/LBT spectra are reported in Mingozzi et al. (2022).
VLT/MUSE: we gathered archival VLT/MUSE IFU data for three CLASSY galaxies J0021+0052 (PI: Anderson), J1044 and J1418 (PI: Dawn Erb) (see Table 1). These observations cover a wavelength from 4300 Å to 9300 Å at a spectral resolution of R ≈ 2000 − 3500, and a field of view (FoV ) of of 1' ×1'. For the analysis of this sample, we have extracted one dimensional spectrum using the same 2.5 HST/COS aperture. As an extra analysis, we have extracted one-dimensional spectra using different aperture sizes ranging from 1 to 4 of diameter in steps of 0.5 . With such spectra, we study the variations of the physical properties with respect to the aperture size. This analysis is discussed in Section 5.5.
We refer to this sample as VLT/MUSE or IFU to distinguish from long-slit spectra. Note that we have extracted the integrated flux using an aperture size of 2.5 resulting in onedimensional spectra.
Keck/ESI: This sample comprises six CLASSY galaxies with high spectral resolution using the Echellette Spectrograph and Imager (ESI) on Keck II. These spectra cover a rest frame wavelength from 3800 Å to 10000 Å approximately, at a spectral resolution of R ≈ 4700 at 1 slit width. The long-slit spectra of these galaxies were obtained from Senchyna et al. (2019) and Sanders et al. (2022).

Emission Line Fluxes
To prepare the spectra for emission line measurements, the optical spectra were corrected by Galactic extinction using the Green et al. (2015) extinction maps included in the PYTHON DUSTMAPS package (Green 2018), and the Cardelli et al. (1989) reddening law. Next, since the Balmer lines are affected by stellar absorption, we model the stellar continuum using Starlight 5 spectral synthesis code (Cid Fernandes et al. 2005) and subtract it. To do so, we follow the successful continuum-subtraction method of the CHAOS survey (Berg et al. 2015) and assume the stellar population models of Bruzual & Charlot (2003) with an initial mass function (IMF) of Chabrier (2003). We use a set of simple stellar populations that span 25 ages (1 Myr-18 Gyr) and six metallicities (0.05 Z < Z < 2.5 Z ).
Using the continuum-subtracted spectra, we fit the emission lines with Gaussian profiles using the Python package LMFIT 6 . Specifically, we simultaneously fit sections of nearby lines (< 200 Å), while constraining the offset from (1) galaxy ID, (2) alternative name, (3-4) coordinates of the objects (J2000), (5) redshift, (6) telescope, instrument or survey for each observation, (7) aperture extraction size, (8) physical size within an aperture size of 3 for SDSS, 2.5 for MUSE and 1 for LBT/MODS, Keck/ESI, and IFU aperture of 2.5 and 3.0 apertures for VLT/MUSE and APO/SDSS, (9) the total galaxy radius represented as (∼ R100/2) and derived using r-band images of Pan-STARRS ) (see also Sec. 5.1) , and (10) references of the sample. line centers and the line width. This method also allows us to simultaneously fit weak and blended lines with a higher degree of accuracy. Since the [O II] λλ3726, 3729 lines are blended in LBT and SDSS observations, we have fitted two Gaussian profiles to constrain the flux measurements in such lines. The errors in the flux were calculated using the expression reported in Berg et al. (2013) and Rogers et al. (2021). Note that for the LBT/MODS spectra of J1044+0353 and J1418+2102, we have adopted the line fluxes reported in Berg et al. (2021). To ensure significant emission line detections, we only use lines with S/N> 3.
The auroral emission lines used to measure temperatures are intrinsically faint and so require careful consideration. Therefore, we inspected the [O III]  λ4363 line can lead differences in metallicity up to 0.08 dex. However, most of objects in the present sample are metal-poor galaxies, but, we Table 2. Physical properties of the 12 CLASSY star-forming galaxies from different apertures analyzed in this work. (1) galaxy ID, (2) instrument/telescope of the observations, (3)-(5) the E(B − V ) values derived using Balmer line ratios Hα/Hβ, Hγ/Hβ and Hδ/Hβ, respectively, (6) the adopted extinction value, E(B − V ), calculated using the weighted mean, (7) the star formation rate derived using Hα luminosity and (8) Fig. 3, we show the resulting spectrum for SDSS, LBT and ESI of J0944-0038 (or SB 2). We have subtracted the continuum from the underlying stellar population, and we have added a small offset for a better comparison of the different spectra.
The different observations for J0944-0038 show the main emission lines used to compute the physical conditions of the nebular gas, namely the electron density and temperature and metallicity. These spectra contain significant He II λ4686, [Ar IV] λλ4711,4740, and [Fe V] λ4227 emission, indicative of a very-high-ionization gas in this galaxy (see dashed lines in Fig. 3). Such very-high-ionization conditions of the gas were reported by Berg et al. (2021) for J1044+0353 and J1418+2102. Additionally, 11 galaxies in our sample have He II and [Ar IV] line detections, but no [Fe V] λ4227 detections. Note that for J0944-0038 (see Fig. 3), there is an odd artefact at ≈5100 Å in the SDDS spectrum that is not detected in the LBT or ESI spectra. This feature is likely an artefact of the SDSS reduction process, but it does not affect our emission-line flux measurements.

Reddening Corrections
Before calculating nebular properties, emission lines must first be corrected for reddening due to dust with the galaxy. To do so, we calculate the color-excess, E(B − V ), for three Balmer decrements (Hα/Hβ, Hγ/Hβ, and Hδ/Hβ) using the expression: where κ(λ) is the value of the attenuation curve at the corresponding wavelength, and (I λ /I Hβ ) theo. and (I λ /I Hβ ) obs. are the theoretical and observed Balmer ratios, respectively. We adopt the reddening law of Cardelli et al. (1989) to calculate κ(λ).
To calculate the color excesses, we use three Balmer ratios, Hα/Hβ, Hγ/Hβ, and Hδ/Hβ, for each galaxy, with a few exceptions (see Sec. 2): • For the MUSE spectra of J1044+0353 and J1418+2102, the limited spectral coverage limits the E(B −V ) calculations to only the Hα/Hβ ratio.
• For the SDSS spectra of J0944-0038, the Hα emission line shows an asymmetric odd extension previously reported by Senchyna et al. (2017), which is not visible in MUSE and ESI spectra.
• For the ESI spectra of J1129+2034, the Hα emission line is saturated and so cannot be used.
• For the ESI spectra of J1148+2546, the Hγ emission line is affected by a detector artifact and so cannot be used.
• For the ESI spectra of J1024+0524, both the Hγ and [O III] λ4363 emission lines are affected by a detector artifact and so cannot be used.
• For the LBT spectra of J1148+2546, the Hδ is affected by an artifact and so cannot be used.
We calculate E(B − V ) values following the approach of , which iteratively calculates the electron temperature and density and E(B − V ) values. We calculate the initial electron temperature using T e [O III] [O III] (λλ4959,5007)/λ4363 when measured, and other available temperature diagnostics when not (e.g., T e [S III] for MUSE). Using this temperature, and assuming the [S II] densities reported in Berg et al. (2022) and Case B recombination, we calculated the theoretical ratios of Hα, Hβ, Hγ and Hδ relative to Hβ. The iterative process stops when the difference in T e ≤ 20 K. Note that in each iteration, the line intensities used to calculate temperature and density were corrected for reddening. For comparison, we have also calculated the E(B − V ) values for the SDSS sample assuming an unique value of T e = 10000 K and n e = 100 cm −3 to derive the theoretical Hα/Hβ, Hγ/Hβ, and Hδ/Hβ ratios (a typical approach for star-forming regions). We find that the difference between this approach and our iterative procedure are up to ∼0.04 dex, in particular, when T e > 10000 K. The uncertainties of the E(B −V ) values were estimated using a Monte Carlo simulation, generating 500 random values and assuming a Gaussian distribution with a sigma equal to the uncertainty of the associated Balmer ratio. The final adopted value of E(B −V ) for each spectrum is the weighted mean after discarding any negative E(B −V ).
In table 2, we list the galaxy ID, the observational data, the E(B − V ) values for each Balmer line ratio (Columns 3-5), and the adopted E(B −V ) value (Column 6). In Section 5, we discuss the differences in E(B − V ) implied by the different Balmer lines with respect to Hβ and other physical properties of CLASSY galaxies.
Finally, emission lines relative to Hβ (I λ /I H β ) were corrected for reddening using the final E(B −V ) values reported in Table 2 and the reddening function f (λ) normalized to Hβ by Cardelli et al. (1989). Note that at optical wavelengths, the variation of extinction with λ are small (Shivaei et al. 2020;Reddy et al. 2016). Therefore, our results are not affected by our choice of the extinction law selected for this sample. The final errors are the result of adding in quadrature the uncertainties in the measurement of the fluxes and the error associated with the fits. We report the resulting emission line intensities for optical spectra analyzed in this work in Table 3. Note that the optical emission lines are reported for the entire CLASSY sample in Mingozzi et al. (2022), but only for a single spectrum per galaxy. Given the comparison of multiple spectra per galaxy in this work, we have remeasured the emission lines of spectra in Mingozzi et al. (2022) for consistency.

PHYSICAL CONDITIONS AND CHEMICAL ABUNDANCES
We use the PyNeb package (version 1.1.14) (Luridiana et al. 2015) in Python to calculate the physical conditions and chemical abundances. We use atomic data for a 5-level atom model (De Robertis et al. 1987). We use the transition probabilities of Froese Fischer & Tachiev (2004) for O + , O 2+ , N + and, S + and of Podobedova et al. (2009) Figure 3. Comparison of the optical spectra of J0944 (or SB 2). These spectra were observed using different instruments with different aperture sizes (APD/SDSS: 3 diameter, LBT/MODS: 1 slit, and Keck/ESI: 1 slit). For a better visual comparison, the flux scale is arbitrarily offset between the spectra. The labels indicate the emission lines used to calculate the physical properties of star-forming galaxies. In the SDSS spectrum, we identify an unknown emission artefact (red x), but note that it does not affect the flux measurements of the emission lines around.
garwal & Keenan (1999) for O 2+ , Tayal (2011)   We also inspected [O II] λλ7320,7330 for possible contamination by telluric absorption bands (Stevenson 1994). For the observations considered here, absorption bands were not detected around the red [O II] lines. Note that due to the redshift of these galaxies, some other lines can also be affected by absorption bands. The [S II] λ6731 line of J1323-0132 of LBT is contaminated by a telluric absorption band, which might impact the results of n e measurement (see Sec 5 for more discussion). Additionally, the strongest emission lines in the optical spectra are at risk of saturating. We, therefore, carried out a visual inspection of the [O III] λ5007 line and also compared its flux to the theoretical ratio of using the theoretical ratio of 2.89 from PyNeb.
In Table 4, we present the results of n e in columns 2-3 and T e in columns 3-7 for the whole sample. The uncertainties were calculated using Monte Carlo simulations in the similar way as E(B −V ).

O/H Abundance
The total oxygen abundance was calculated by summing the contribution of O + /H + + O 2+ /H + . We neglected any contribution of O 3+ /H + to O/H at it is negligible ). The uncertainties were calculated using Monte Carlo simulations by generating 500 random values assuming a Gaussian distribution with sigma associated with the uncertainty. In Table 4, we list the results of 12+log(O/H) in column 12 for the whole sample. In addition, in Table 5, we present the results of metallicity for the multiple apertures in columns 2-5, and the differences in metallicity, ∆O/H = O/H IFU, long−slit − O/H SDSS in columns 6-8.
For the rest of the sample (ESI and MUSE spectra and some SDSS spectra), we obtained O 32 using the emissivities of [O II] λ3727 and [O II] λλ7320,7330 using PyNeb. Such emissivities were calculated using T e (low) associated to the low ionization emitting zone (see Table 8). We derived a representative factor between both [O II] lines in the red and blue ranges for each galaxy. To estimate the intensity of [O II] λ3727 estimated , we used the observed emission lines of [O II] λλ7320,7330 multiplied for the factor calculated from the emissivity ratio of j[O II] λ3727/ j[O II] λλ7320,7330, for each galaxy. In Table 6, we list the results of O 32 for our sample of galaxies. We have identified those galaxies of SDSS sample with estimates of [O II] λ3727 with an asterisk, ' * '.

DISCUSSION
In this section, we discuss the results implied for the different apertures obtained for CLASSY galaxies in Secs. 3 and 4, related to EW, ionization parameter, extinction, SFR, and metallicity.
In panels (a) and (b) of Fig. 5, we show the comparison between EWs of [O III] and Hα derived using SDSS spectra and those results using long-slit and IFU spectra of LBT, ESI and MUSE. Overall, we find consistent results among the different setups with differences lower than 0.07 dex for EW(Hα) with respect to SDSS EW(Hα), except for J1132+5722 that shows a difference of 0.2 dex. However, for EW([O III]), the differences can reach up to 0.2 dex for ESI and LBT spectra, and for MUSE the differences can reach up to 0.1 dex with respect to SDSS EW([O III]). These differences can be due to the different apertures collecting different relative amounts of nebular emission and stellar continuum.
We also find that in most galaxies, the percentage of light covered is larger than 60% for apertures of 3 and 2. 5. For long-slit LBT and ESI spectra, the light enclosed within such aperture ranges between 20% and 60%. We also note that for J1129+2034 and J1132+5722, their percentage is lower than 20% for either IFU (∼ 30%) of long-slit apertures. In fact, those galaxies have an elongated form (see top panel of Fig. 6). However, the observations for those galaxies are where the peak of star formation is located.

Ionization parameter comparison
We have analyzed the variations of the ionization parameter with aperture size. Overall, we find that differences in log(O 32 ) can reach values up to ∼0.14 dex. There are some exceptions with differences larger than 0.2 dex. Note that part of these large differences might be due to the estimate of [O II] λ3727 using the [O II] λλ7320,7330 lines.
To check this, we compare the values of O 32 for the galaxies of the SDSS and LBT sample for which the [O II] λ3727 emission lines are available. Such galaxies are J0808+3948, J1148+2546, and J1545+0858. We find that the differences calculated are up to 0.14 dex, except for J1148+2546 that shows a differences of 0.08 dex. In this case, the LBT spectrum provides higher values of O 32 than the SDSS spectrum. Part of these differences might be due to the sampled region within the galaxy. However, we find the same result for J1148+2546 using the ESI spectrum (see Table 6).

E(B −V ) aperture comparison
The results presented in Table 2 provide a broad picture of the variations derived using Balmer ratios to calculate the reddening of this sample of star-forming galaxies. In . Fig 7, we show the behavior of Hα/Hβ, Hγ/Hβ, and Hδ/Hβ and the adopted value of E(B −V ) for SDSS, ESI, and LBT apertures. The X-axis shows the 12 galaxies studied here ordered by increasing metallicity. The different symbols indicate the Balmer ratio used to estimate E(B − V ) using Eq. 1. We discarded the results of MUSE because of the missing coverage of Hγ/Hβ and Hδ/Hβ for J1044+0353 and J1418+2102.
In general, SDSS, ESI, and LBT observations show no variation distribution of E(B − V ) with respect to metallicity for the different estimates of E(B −V ) using Balmer lines. The dashed lines in the top panels of Fig. 7 indicate the mean values of E(B −V ) for each set of observations in color code with the symbols, including the adopted values of E(B − V ). Such values, mean, and dispersion for the results of E(B −V ) using Balmer ratios are reported in Table 7. Note those estimates of the dispersion of E(B −V ) in Table 7 depends on the  Fig. 7. The E(B − V ) shows the mean and dispersion value for the whole sample of observations in each instrument, SDSS, LBT, and ESI. number of galaxies with measurements of Hα/Hβ, Hγ/Hβ, and Hδ/Hα available in the observed spectra. For the SDSS sample, we find similar values within the uncertainties implied for the different Balmer ratios used. In Fig. 7, it is observed that the SDSS spectra with an aperture size of 3 show less scatter and lower uncertainties in the E(B − V ) implied by the different Balmer line ratios in comparison to those obtained using long-slit spectra. In addition, it seems LBT results show systematic effects for individual E(B − V ) results, but the adopted E(B − V ) is consistent with SDSS results.
For LBT spectra, E(B − V ) derived using Hγ/Hβ and Hδ/Hβ show higher values with respect to Hα/Hβ in comparison to SDSS and ESI. For example, such differences implied in the E(B −V ) estimate might be due to stellar continuum subtraction. In H II regions of local disk galaxies, the discrepancy between Hα/Hβ and Hγ/Hβ and Hδ/Hβ have been reported in different works, impliying that this issue is common in other environments (Croxall et al. 2016;Rogers et al. 2021).
On the other hand, some of the results of E(B − V ) provide negative reddening calculated for some spectra of SDSS and ESI (see Fig. 7 and Table 2), derived using Hγ/Hβ and Hδ/Hβ. Previously, Kewley et al. (2005) found similar behavior for some galaxies of their sample. These authors pointed out as possible cause the errors in the stellar subtraction, flux calibrations and uncertain measurements due to noise. However, those values should agree within the errors. We have revised the emission lines fitting in those spectra with negative E(B − V ) around Hγ and Hδ. In general, the range in a wavelength where those lines are located shows no apparent issues in the flux measurements of those Balmer lines. However, we do not exclude that stellar continuum subtraction might affect the flux measured in those lines as was suggested by Groves et al. (2012). In an incoming pa- 12- Figure 6. Top: The SDSS r-band images of four galaxies of this sample (see also Fig. 1). The 2.5 MUSE aperture and the 1 LBT and ESI apertures are shown as a magenta circle and green and orange boxes, respectively. The 3 SDSS aperture is also shown as a cyan circle, and the dotted circle represents the total galaxy radius defined as R100/2 (see Table 1 and Sec. 5.1). Bottom: Comparison of log EW of [O III] (a) and Hα (b) for the SDSS, MUSE, LBT, and ESI apertures versus the fraction of total optical light enclosed by the respective spectral aperture, Aaper/A R 100 /2 . The results of the EWs are reported in Table 2. The numbers identify the ID number of the galaxy listed in Table 1. per, we will assess the impact of the reddening correction implied by Balmer and Paschen lines calculating E(B − V ) (Rogers et al. 2021;Méndez-Delgado et al. 2021;Aver et al. 2021) using a different set of observations of CLASSY. In particular, the LBT observations of this paper (see Fig. 2), which cover a wide range in wavelength. It allows analyzing the in much more detail the reddening correction, dust geometry (Scarlata et al. 2009), the ionization structure of the gas, the electron density and temperature using different diagnostics, chemical abundances of different ions and the very high ionization emission lines ). Now, we show the comparison of different apertures implied in the results of the adopted E(B −V ) with respect to the SDSS results, which it shown in Fig. 8. The symbols represent the observations implied for the different apertures, and the dashed line indicates the 1:1 relationship. In general, the differences, ∆E(B − V ) = E(B − V ) IFU, long−slit − E(B − V ) SDSS are lower than 0.1 dex for most of the observations (see also Table 2).
Finally, we also compare the reddening derived by averaging the values from three different Balmer line ratios E(B-V) adopted ) as a function [O III] λ5007 and Hα EWs. In Fig. 9, we show the comparison between the differences between the E(B-V) adopted values and the EWs of [O III] λ5007 (a) and Hα (b) with respect to the SDSS results. We find that at least for the range implied for this sample, E(B − V ) versus EWs seems to be constant. Note that the E(B −V ) versus EW([O III]) shows a larger dispersion than EW([Hα]), although for a different number of galaxies (see Table 2). However, the difference for LS and IFU sample are lower than 0.1 dex for most of the galaxies for either IFU or LS apertures.

Density, temperature, and metallicity comparison
Here, we analyze if the use of different apertures impacts the physical condition and chemical abundance determinations. In principle, both density and temperature di- , and ESI (c) spectra, where the symbols represent each instrument, stars, circles, and squares, respectively. The galaxies are ordered at increasing metallicity, see Table 5. The symbols indicate the E(B − V ) values derived using the Balmer decrement (teal, orange, and blue) and the final E(B − V ) values (purple, see Table 2). The dashed lines represent the mean values of E(B − V ) derived using the Balmer lines and the adopted E(B −V ) value for each observation (see Table 7). observations (see also Sec. 4). It is important to evaluate only the differences indicated for aperture effects. For density, it was possible to obtain measurements for all the multiple apertures using [S II] intensities (see Table 4 and Sec.4). In principle, We use SDSS observations as a comparison sample for our results from the other instruments. The reason is that for SDSS, we can measure most of the physical properties of each galaxy, and because the aperture implied in SDSS (3 ) sample is mapping a similar emission region to that of the HST/COS aperture (2.5 ). For the SDSS sample, we obtain densities of 50 < n e (cm −3 ) < 1100. J0808+3948, J1044+0353, and J1323-0132 show high values of n e > 300 cm −3 in comparison with the rest of the sample. In panel (a) of Fig. 10, we show the comparison of the results for n e < 300 using SDSS spectra versus the densities calculated using the multiple spectra (we discard the high-density values for display purposes corresponding to J0808+3849 and J1323-0132). We find that at low density, n e < 150 cm −3 , where more of the CLASSY galaxies are located, long-slit observations show consistent results within the uncertainties with the SDSS sample. For J0808+3948 and J1044+0353, with high-density values, LBT and SDSS observations show small differences of 40 and 100 cm −3 , respectively.
In our first analysis of the electron density for J1323-0132 of LBT, we find a difference of 370 cm −3 in comparison to SDSS aperture. We note that the observed wavelengths of the [S II] lines in J1323-0132 are affected by telluric absorption. We fitted those lines again, taking into account the absorption respectively. Note that the results for EWs(Hα) correspond to those spectra with measurements of Hα (see Table 2).
feature. For J1323-0132, we calculate a new value of n e = 640 +800 −500 cm −3 , which implies a difference of 50 cm −3 with respect to the previous contaminated value. In Table 8, we show the differences in density, temperature and metallicities of IFU and LS apertures concerning SDSS measurements. Those galaxies with multiple apertures using IFU and LS are also indicated in Table 8 for comparison (J1044+0353 and J1418+2102). In general, we find that n e [S II] implied for the different apertures are in good agreement with those results of SDSS aperture with differences lower than 100 cm −3 .
On the other hand, we have calculated n e [ O II] cm −3 for some galaxies. It includes the whole sample of the LBT observations and four galaxies of SDSS (J0021+0052, J1024+0524, J1044+0353, and J1545+0858, see also Table 4). Firstly, we compare the results between the density diagnostics of n e [ O II] and n e [ S II] derived for the LBT spectra. Overall, we find differences lower than 100 cm −3 for most of the LBT sample. The exception is J0021+0052 and J0808+3948 whose difference is up 470 cm −3 . In similar way, the four galaxies with n e [ O II] show differences of up to ∼ 210 cm −3 . Note that the density diagnostic of n e [ O II] provides values higher than the results implied by n e [ S II] in both samples. Next, we compare the results implied by n e [ O II] for two galaxies in common in the LBT and SDSS sample (J1148+2546 and J1548+0858). We find differences lower than 80 cm −3 .
Concerning the electron temperature, we have calculated T e ([O III]) and T e ([S III]) for most of the spectra of CLASSY galaxies (see Table 4). T e ([O III]) was measured in the whole SDSS sample (with the exception of J0808+3948) and in some galaxies for the rest of the observations with different apertures. In panel (b) of Fig. 10 for IFU and long-slit apertures are consistent with SDSS results with differences lower than 700 K for most of the objects (see Table 8). J1132+5722 of ESI sample show a difference of −1500 K in T e ([O III]) with respect to SDSS measurements. This large discrepancy might be related to the measurement of [O III] λ4363 or due to spatial variations. Note that our comparison to SDSS results is due to analysis of the variations of the physical properties in each galaxy with respect to other apertures. Therefore, it does not imply that the temperatures or the different physical conditions of the SDSS sample are the true values since they might also be affected by different bias (i.e., observational problems). For the objects with S/N ([S III]) > 3, we computed T e ([S III]) implied by SDSS, LBT, ESI, and MUSE apertures. We find that T e ([S III]) calculated using MUSE spectra provides higher temperatures with respect to SDSS results (see Table 8). In particular, J1044+0353 shows a difference of up to 6100 K with respect to T e ([S III]) implied by SDSS and LBT spectra. In fact, T e ([S III]) derived using LBT also shows a higher value than SDSS. In panel (c) of Fig. 10, we show the comparison between T e ([S III]) derived using SDSS sample and IFU and long-slit apertures. In that figure, the results using MUSE and LBT for J1044+0353 are represented by a rhomboid and circle, which are joined by a dotted line. We find that the difference between these two measurements and the results of SDSS is up to 6100 K (see Table 8). These discrepancies might be due to telluric absorption affecting [S III] λ9069, the only line available in the MUSE spectra. In general, we find differences in T e ([S III]) lower than 800 K.
Since metallicity is an important measure in star-forming galaxies, we analyze the impact to use multiple aperture sizes for the same galaxy in the computation of metallicity. One of the main advantages of the sample of CLASSY galaxies studied here is the availability of measurements of electron temperature, which allows a better constraint on the estimated chemical abundance determinations. In Fig. 11, we show the comparison between the metallicities calculated by the different apertures and those by SDSS aperture. Long-slit spectra correspond to the squares and circles, while the rhomboids correspond to an aperture similar to SDSS and HST/COS. In general, our results show that LS apertures (most of the sample have aperture sizes of ≈ 1 × 2 ) are consistent with the results implied by the 3.0 aperture of SDSS sample within the uncertainties with differences generally lower than 0.08 dex. However, we find a difference in metallicity in using ESI spectra. Such discrepancies are mainly related to the larger differences that we found for T e ([O III]) (see Table 8).
In principle, it is expected that results obtained from MUSE agree with SDSS given that the apertures map similar emission. For the three galaxies with MUSE observations, J0021+0052, J1044+0353, and J1148+2546, we find differences in metallicity lower than 0.06 dex, with the exception of J1044+0353 with a difference of 0.16 dex (see Table 8). The reason for this difference might due to the estimate of T e ([O III]) by the temperature relation in Eq. 3. J1044+0353 is an extremely high ionization galaxy showing a large amount of high ionization species  In summary, we find a good agreement between IFU and LS apertures for the different physical properties derived for this sample of CLASSY galaxies. The galaxies studied here are mainly dominated by a single bright star formation cluster. Therefore, it is expected that such differences be minimal. Another point is that despite instrumental effects and systematic differences between instruments, we are getting the same results.
On the other hand, since the computation of T e depends on the T e -diagnostic available in the emission spectra of each galaxy, it is important to have a reliable constraint of the temperature and ionization structure of the nebular gas. Therefore, this analysis supports comparing the physical properties obtained using optical data with those results used to constrain UV analysis for the aperture of different sizes with similar characteristics to the CLASSY sample (Mingozzi et al. 2022).

Aperture analysis using MUSE
As an extra analysis, we have taken advantage of the integrated spectra obtained from MUSE using different aperture sizes for J0021+0052, J1044+0353, and J1418+2102. This new set of spectra comprises sizes between 1.0 and 7.5 of diameter with steps of 0.5 . We analyzed the variations of E(B − V ), n e , T e , ionization parameter, metallicities, SFR, and EWs as result of the different aperture sizes derived from MUSE.
We have calculated the SFR using the Hα flux measurements obtained in each MUSE apertures. We use E(B-V) adopted values in each aperture to correct Hα fluxes for extinction. The luminosity distances were taken from Berg et al. (2022; see their Table 5), which consider peculiar motions due to the low redshift of the CLASSY galaxies. To estimate SFR, we use the expression reported by Kennicutt & Evans (2012): log SFR(L(Hα)) = log L(Hα) -41.27. This expression is based on updated stellar models and initial mass function fit by Chabrier (2003) (mass range 0.1-100 M ). SFR uncertainties were calculated using error propagation.
In Fig. 12, we show the results for the integrated MUSE spectra using a different aperture size. The triangles, circles, and squares represent J0021+0052, J1044+0353, and J1418+2102, respectively. For comparison, we have added the results derived from SDSS spectra, which are shown in each panel of Fig. 12 with empty stars with the same color as their respective galaxy. The two vertical bars represent the aperture size of HST/COS and SDSS of 2.5 and 3.0 respectively. Overall, Fig. 12 shows that the variations of the galaxy properties convergent at an aperture size of 4 , implying that most of the flux can be in-closed at similar aperture sizes to SDSS (3 ) and COS (2.5 ) apertures for these galaxies. In panels (a) to (e), we compared each individual spectrum as a function of the extinction, the physical conditions (n e and T e ) and metallicity. In general, we find consistent results through the multiple aperture sizes. We note that for J0021+0052 the extinction calculated using Hα/Hβ shows a difference of 0.15 dex when 1.0 and 3.0 aperture are compared, increasing such difference as the aperture becomes bigger. However, we find a smooth variation of E(B − V ) for J10144+0353 and J1418+2102 with respect to the different aperture sizes. We also calculated E(B − V ) using Hγ/Hβ for J0021+0052 (see blue triangles in panel (a) of Fig. 12.), showing a similar behavior in comparison to the other two galaxies in this analysis. In fact, the results for SDSS show a good agreement with those obtained using 2.5 aperture size.
We also find that the electron density and temperature, and metallicity show slight variations in their results for the different aperture sizes (see panels (b)-(e) of Fig. 12). For J1044+0353 and J1418+2102, the only temperature diagnostic available is T e ([S III]), whose results are in excellent agreement with the rest of MUSE aperture sizes implied in this analysis. For J1044+0353, the result for T e ([S III] show a large difference between MUSE and SDSS data (see Table 8). In Sec. 5.4, we stress that such a difference could be due attributed to the telluric features affecting the [S III] λ9069 emission line.
In Panel (d) of Fig. 12 (e) shows small variations of metallicity as the aperture size increases. Moreover, SDSS spectra show a good agreement with the values of O/H derived either using an aperture of 2.5 or 3.0 . In panel (f) of Fig. 12, we compare the variations of the ionization parameter measured as a proxy of S3S2 = [S III] (λ9069+ λ9532)/[S II] (λ6717 + λ6731) (see e.g., Berg et al. 2021;Mingozzi et al. 2022), which trace the low ionization emitting zone of the nebula. We have used this approach because [S II] and [S III] are directly available for J1044+0353 and J1418+2102 in MUSE spectra. We find that log(S3S2) decreases until reach a convergence when the aperture size is also ∼ 4 of diameter. For J1418+0858, we find a small difference between the MUSE and SDSS results of 0.03 dex for an aperture size of 3 . However, the log(S3S2) obtained with MUSE shows a large difference with respect to the SDSS value (see also panel (c) in Fig. 12), probably associanted with the measurement of the [S III] (λ9069) line as we have discussed in Sec. 5.4.
Finally, we compare SFR and EWs of Hα and [O III] for each aperture, see panels (f) to (h) of Fig. 12. Although, we find small changes in the inferred SFRs at a given aperture size, note that for apertures smaller than 1.5 we obtained slightly lower values of SFR for J0021+0052, J1044+0353, and J1418+2102. Moreover, the SFR and EWs converge  Fig. 12 such a structure is not visible) followed by an increase of EW at an aperture of 1.5 . Such behavior might be related to the complex structure into the core of J0021+0052.

SUMMARY AND CONCLUSIONS
A key goal of the CLASSY sample is to provide a unified picture of the stars and gas with in nearby star-forming galaxies, which is largely derived from their FUV spectra. However, optical spectra that are well matched to the FUV spectra are also needed to derive a number of important nebular properties. We, therefore, analyzed the impact of aperture differences on the determination of nebular properties of 12 local star-forming galaxies at z < 0.098 for the CLASSY sample. This sample was chosen to have multiple optical spectra, including circular aperture, long-slit, and IFU spectroscopy. Specifically, we investigated the nebular properties of reddening, electron density and temperature, metallicities, ionization, and nebular to stellar emission as probed by Hα and [O III] λ5007 equivalent width. In principle, the 3 diameter SDSS aperture is expected to cover most of the emission of CLASSY galaxies and is well-matched to the FUV spectra observed with the HST/COS 2. 5 aperture. Therefore, we use the SDSS spectra as our base of comparison for our the other optical spectra. Additionally, the IFU spectra allow us to inspect how the derived properties change as a function of aperture-extraction size, while eliminating any instrument effects. We summarize our main conclusions as follows.
1. We have calculated the reddening using three different Balmer ratios (Hα/Hβ, Hγ/Hβ, and Hδ/Hβ) and found that the error-weighted average E(B-V) value was insensitive to aperture size of different spectra for our sample, with a median difference of less than 0.1 dex.
However, using the IFU observations of 3 CLASSY galaxies, we find that the E(B-V) values derived from individual Balmer line ratios decrease (by up to 53%) with increasing aperture size, with the most significant change occurring in the center of the galaxies.
2. We calculated electron densities [S II] λλ6717,6731 and temperatures from multiple auroral lines and found them to be insensitive to aperture size for our sample. In particular, investigating a range of aperture-extraction sizes from the IFU observations, we find that values change most significantly in the center of the galaxies, and level out near the COS aperture radius of 2. 5. Similar results were found for reddening and metallicity, 3. We find a good agreement between the metallicities derived using the various aperture spectra for the same galaxy, with differences of <0.1 dex. Such small differences imply that the metallicity calculated from the optical spectra is representative of the region sampled in the FUV with COS for our CLASSY sample of the star-forming galaxies.
To summarize, we find that the aperture effects on inferred nebular properties are minimal for the CLASSY sample of star-forming galaxies. Here we want to stress that despite the specific instrumental effects imprinted on the spectra, we find quite similar results. These results demonstrate the appropriateness of comparing the physical properties obtained in the optical for compact, highly-star-forming galaxies with those using the 2.5 aperture of HST/COS (Mingozzi et al. 2022). Figure 12. MUSE IFU aperture variations. Integrated MUSE spectra using aperture sizes from 1.0 to 7.5 of diameter in steps of 0.5 for J0021+0052, J1044+0353, and J1418+2102. The different symbols indicate the results for J0021+0052 (triangles), J1044+0353 (circles), and J1418+2102 (squares). For comparison, we add the results using SDSS aperture of 3.0 (stars and cyan bar) spectra for those galaxies. We identify the aperture size of HST/COS of 2.5 (pink bar). Panel (a) shows the reddening derived using Hα/Hβ and Hγ/Hβ (only for J0021+0052 in blue triangles). Panels (b)-(e) show the variation of electron density (ne), electron temperature ( The CLASSY team thanks the referee for thoughtful feedback that improved the paper. KZA-C and DAB are grateful for the support for this program, HST-GO-15840, that was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Associations of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. The CLASSY collaboration extends special gratitude to the Lorentz Center for useful discussions during the "Characterizing Galaxies with Spectroscopy with a view for JWST" 2017 workshop that led to the formation of the CLASSY collaboration and survey. The CLASSY collaboration thanks the COS team for all their assistance and advice in the reduction of the COS data. KZA-C also thanks Noah Rogers for his help with the MODS data reduction for LBT spectra and Víctor Patiño-Álvarez and Héctor Ibarral-Medel for their helpful discussions in the use of STARLIGHT code. BLJ is thankful for support from the European Space Agency (ESA). JB acknowledges support by Fundação para a Ciência e a Tecnologia (FCT) through the research grants UIDB/04434/2020 and UIDP/04434/2020, through work contract No. 2020.03379.CEECIND, and through FCT project PTDC/FISAST/4862/2020. RA acknowledges support from ANID Fondecyt Regular 1202007.
This work also uses observations obtained with the Large 11 Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society,The Leibniz Institute for Astrophysics Potsdam, and Hei-delberg University; The Ohio State University, University of 19 Notre Dame, University of Minnesota, and University of Virginia.
The STARLIGHT project is supported by the Brazilian agencies CNPq, CAPES and FAPESP and by the France-Brazil CAPES/Cofecub program. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science.
The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan Table 11. Deredened emission line intensities measured for the VLT/MUSE spectra for Three CLASSY galaxies.