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{"Abstract":["This file contains simple stellar population (SSP) model spectra constructed from a version of the SDSS-IV MaNGA Stellar Library (MaStar; Yan et al. 2019, Abdurro'uf et al. 2022) that has been corrected for the effects of absorption in the CaII 3934, 3969 and NaI D 5891, 5897 transitions arising in the Milky Way's interstellar medium (ISM).  These corrections are described in full in Rubin et al. (2025), and our approach to constructing these SSP models is described in Maraston et al. (2020) and Rubin et al. (2025).  In brief, our models are calculated with the evolutionary population synthesis code of Maraston (2005), which is based on the fuel consumption theorem for the evaluation of the energetics of post-Main Sequence phases.  We use the calibrated median values of the stellar parameters calculated for the MaStar sample to generate representative stellar spectra as functions of effective temperature, surface gravity, and chemical composition.  These representative spectra are then used as input for the stellar population models.  The stellar parameter estimates are described in R. Yan et al. (2025, in preparation) and at https://www.sdss4.org/dr17/mastar/mastar-stellar-parameters/.  \n\nWe calculate SSPs using stars in metallicity bins centered at [Z/H] = -1.35, -0.33, 0.0, and +0.35 with an approximate bin width of 0.1 dex assuming a Salpeter IMF.  The SSP ages span 3 Myr to 15 Gyr and are calculated at 51 gridpoints.  For comparison, we also calculate the equivalent SSPs using the uncorrected MaStar spectra.  The datamodel is described below.\n\nHDU1: 51 x 4 x 1 x 3 matrix describing the parameters of each SSP spectrum.  Each gridpoint (i,j,k) contains a 3-element array listing the age (in Gyr), metallicity, and IMF slope (in linear mass units)\n\nHDU2: 2 x 4563 array containing the vacuum wavelength and spectral resolution (R) grids for models constructed from the uncorrected (original) stellar library.  The wavelength sampling is logarithmic and the wavelengths have units of Angstroms.  R = wave / (FWHM dwave)\n\nHDU3: 51 x 4 x 1 x 4563 matrix containing the SSPs constructed from the uncorrected (original) stellar library in units of erg/s/Ang/Msun  \n\nHDU4: 2 x 4542 array containing the vacuum wavelength and spectral resolution (R) grids for models constructed from the corrected (cleaned) stellar library.  The wavelength sampling is logarithmic and the wavelengths have units of Angstroms.  R = wave / (FWHM dwave)\n\nHDU5: 51 x 4 x 1 x 4542 matrix containing the SSPs constructed from the corrected (cleaned) stellar library in units of erg/s/Ang/Msun  "],"Other":["Preferred Citation\n\nIf you use these model spectra in your research, we ask that you please cite our article, "Sloan Digital Sky Survey IV MaStar: Quantification and Abatement of Interstellar Absorption in the Largest Empirical Stellar Spectral Library," Rubin et al. (2025), ApJ, 981 31, doi:10.3847/1538-4357/ad8eb6.  Please also cite this Zenodo deposit."]} 

Abstract We assess the impact of Caiiλλ3934, 3969 and Naiλλ5891, 5897 absorption arising in the interstellar medium (ISM) on the Sloan Digital Sky Survey-IV MaNGA Stellar Library (MaStar) and produce corrected spectroscopy for 80% of the 24,162-star catalog. We model the absorption strength of these transitions as a function of the stellar distance, Galactic latitude, and dust reddening based on high-spectral resolution studies. With this model, we identify 6342 MaStar stars that have negligible ISM absorption (W^ISM(CaiiK) < 0.07 Å andW^ISM(Nai5891) < 0.05 Å). For 12,110 of the remaining stars, we replace their NaiD profile (and their Caiiprofile for effective temperaturesT_eff> 9000 K) with a coadded spectrum of low-ISM stars with similarT_eff, surface gravity, and metallicity. For 738 additional stars withT_eff> 9000 K, we replace these spectral regions with a matching ATLAS9-based BOSZ model. This results in a mean reduction inW(CaiiK) (W(NaiD)) of 0.4–0.7 Å (0.6–1.1 Å) for hot stars (T_eff> 7610 K), and a mean reduction inW(NaiD) of 0.1–0.2 Å for cooler stars. We show that interstellar absorption in the simple stellar population (SSP) model spectra constructed from the original library artificially enhancesW(CaiiK) by ≳20% at young ages (<400 Myr); dramatically enhances the strength of stellar NaiD in starbursting systems (by ≳50%); and enhances stellar NaiD in older stellar populations (≳10 Gyr) by ≳10%. We provide SSP spectra constructed from the cleaned library and discuss the implications of these effects for stellar population synthesis analyses constraining the stellar age, [Na/Fe] abundance, and initial mass function. 

{"Abstract":["This file contains a version of the SDSS-IV MaNGA Stellar Library (MaStar) which has been corrected for the effects of absorption in the CaII 3934, 3969 and NaI D 5891, 5897 transitions arising in the Milky Way's interstellar medium (ISM).  These corrections are described in full in Rubin et al. (2025).  In brief, we first develop a model of the absorption strengths of these transitions as a function of stellar distance, Galactic latitude, and dust reddening based upon high-spectral resolution studies.  We use this model to identify 6342 MaStar stars with negligible ISM absorption.  For 12110 of the remaining stars, we replace their NaI D profile (and their CaII profile for effective temperatures > 9000 K) with a coadded spectrum of low-ISM stars with similar effective temperature, surface gravity, and metallicity.  For 738 additional stars with effective temperatures > 9000 K, we replace these spectral regions with a matching ATLAS9-based BOSZ model.  This procedure yields corrected spectroscopy for 80% of the 24162-star catalog.\n\nThe spectra in this file are identical to those which have been unified to the 99.5th-percentile spectral resolution curve for MaStar and made available at https://www.sdss4.org/dr17/mastar/mastar-spectra (with the exception of the corrected spectral regions described above).  The datamodel is described below.    \n\nMANGAID - The XX-XXXXXX format MaNGA IDWAVE - Vacuum wavelength grid. The wavelength sampling is logarithmic (Angstroms)FLUX - Observed flux, corrected for Milky Way ISM contamination.  Extinction-corrected to above the Earth's atmosphere but not corrected for Galactic extinction (10^-17 erg/s/cm^2/Ang)IVAR - Inverse variance of the flux (10^34 s^2cm^4Ang^2/erg^2)PREDISP - Instrumental broadening sigma.  Does not include the effect of pixel integration (Angstroms)SRES - Spectral resolution = WAVE/(sqrt(8*ln(2)) * PREDISP)REPLACEMENT_CAII_FLG - Flag indicating treatment of the CaII spectral region.  Described in Table 3REPLACEMENT_NAID_FLG - Flag indicating treatment of the NaID spectral region.  Described in Table 3NSIG_THRESH - Maximum 3D distance in stellar parameter space from stars included in empirical replacement stack, if one was constructed.  Described in Sec. 3.1 and 3.2 (Psi_thresh)ewCaIIK_pred - Interstellar CaII K EW predicted by model described in Sec. 2.2 (Angstroms)ewNaI5891_pred - Interstellar NaI D 5891 EW predicted by model described in Sec. 2.2 (Angstroms)ewNaI5897_pred - Interstellar NaI D 5897 EW predicted by model described in Sec. 2.2 (Angstroms)"],"Other":["Preferred Citation\n\nIf you use these library spectra in your research, we ask that you please cite our article, "Sloan Digital Sky Survey IV MaStar: Quantification and Abatement of Interstellar Absorption in the Largest Empirical Stellar Spectral Library," Rubin et al. (2025), ApJ, 981 31, doi:10.3847/1538-4357/ad8eb6.  Please also cite this Zenodo deposit."]}