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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."]} 

Abstract The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are the closest massive satellite galaxies of the Milky Way. They are probably on their first passage on an infalling orbit towards our Galaxy 1 and trace the continuing dynamics of the Local Group 2 . Recent measurements of a high mass for the LMC ( M halo  ≈ 10 11.1–11.4   M ⊙ ) 3–6 imply that the LMC should host a Magellanic Corona: a collisionally ionized, warm-hot gaseous halo at the virial temperature (10 5.3–5.5  K) initially extending out to the virial radius (100–130 kiloparsecs (kpc)). Such a corona would have shaped the formation of the Magellanic Stream 7 , a tidal gas structure extending over 200° across the sky 2,8,9 that is bringing in metal-poor gas to the Milky Way 10 . Here we show evidence for this Magellanic Corona with a potential direct detection in highly ionized oxygen (O +5 ) and indirectly by means of triply ionized carbon and silicon, seen in ultraviolet (UV) absorption towards background quasars. We find that the Magellanic Corona is part of a pervasive multiphase Magellanic circumgalactic medium (CGM) seen in many ionization states with a declining projected radial profile out to at least 35 kpc from the LMC and a total ionized CGM mass of log 10 ( M H II,CGM / M ⊙ ) ≈ 9.1 ± 0.2. The evidence for the Magellanic Corona is a crucial step forward in characterizing the Magellanic group and its nested evolution with the Local Group. 

Abstract This study addresses how the incidence rate of strong Oviabsorbers in a galaxy’s circumgalactic medium (CGM) depends on galaxy mass and, independently, on the amount of star formation in the galaxy. We use Hubble Space Telescope/Cosmic Origins Spectrograph absorption spectroscopy of quasars to measure Oviabsorption within 400 projected kpc and 300 km s⁻¹of 52 galaxies withM_*∼ 3 × 10¹⁰M_⊙. The galaxies have redshifts 0.12 <z< 0.6, stellar masses 10^10.1M_⊙<M_*< 10^10.9M_⊙, and spectroscopic classifications as star-forming or passive. We compare the incidence rates of high column density Oviabsorption (N_OVI≥ 10^14.3cm⁻²) near star-forming and passive galaxies in two narrow ranges of stellar mass and, separately, in a matched range of halo mass. In all three mass ranges, the Ovicovering fraction within 150 kpc is higher around star-forming galaxies than around passive galaxies with greater than 3σ-equivalent statistical significance. On average, the CGM of star-forming galaxies withM_*∼ 3 × 10¹⁰M_⊙contains more Ovithan the CGM of passive galaxies with the same mass. This difference is evidence for a CGM transformation that happens together with galaxy quenching and is not driven primarily by halo mass. 

Abstract We combine data sets from the CGM²and CASBaH surveys to model a transition point,R_cross, between circumgalactic and intergalactic media (CGM and IGM, respectively). In total, our data consist of 7244 galaxies atz< 0.5 with precisely measured spectroscopic redshifts, all having impact parameters of 0.01–20 comoving Mpc from 28 QSO sightlines with high-resolution UV spectra that cover HiLyα. Our best-fitting model is a two-component model that combines a 3D absorber–galaxy cross-correlation function with a simple Gaussian profile at inner radii to represent the CGM. By design, this model gives rise to a determination ofR_crossas a function of galaxy stellar mass, which can be interpreted as the boundary between the CGM and IGM. For galaxies with 10⁸≤M_⋆/M_⊙≤ 10^10.5, we find thatR_cross(M_⋆) ≈ 2.0 ± 0.6R_vir. Additionally, we find excellent agreement betweenR_cross(M_⋆) and the theoretically determined splashback radius for galaxies in this mass range. Overall, our results favor models of galaxy evolution atz< 0.5 that distributeT≈ 10⁴K gas to distances beyond the virial radius. 

Abstract We present the KODIAQ-Z survey aimed to characterize the cool, photoionized gas at 2.2 ≲z≲ 3.6 in 202 Hi-selected absorbers with 14.6 ≤ $\log N_{\mathrm{H}\mathrm{I}}$< 20 that probe the interface between galaxies and the intergalactic medium (IGM). We find that gas with $14.6\le \log N_{\mathrm{H}\mathrm{I}}<20$at 2.2 ≲z≲ 3.6 can be metal-rich (−1.6 ≲ [X/H] ≲ − 0.2) as seen in damped Lyαabsorbers (DLAs); it can also be very metal-poor ([X/H] < − 2.4) or even pristine ([X/H] < − 3.8), which is not observed in DLAs but is common in the IGM. For $16<\log N_{\mathrm{H}\mathrm{I}}<20$absorbers, the frequency of pristine absorbers is about 1%–10%, while for $14.6\le \log N_{\mathrm{H}\mathrm{I}}\le 16$absorbers it is 10%–20%, similar to the diffuse IGM. Supersolar gas is extremely rare (<1%) at these redshifts. The factor of several thousand spread from the lowest to highest metallicities and large metallicity variations (a factor of a few to >100) between absorbers separated by less than Δv< 500 km s⁻¹imply that the metals are poorly mixed in $14.6\le \log N_{\mathrm{H}\mathrm{I}}<20$gas. We show that these photoionized absorbers contribute to about 14% of the cosmic baryons and 45% of the cosmic metals at 2.2 ≲z≲ 3.6. We find that the mean metallicity increases withN_Hi, consistent with what is found inz< 1 gas. The metallicity of gas in this column density regime has increased by a factor ∼8 from 2.2 ≲z≲ 3.6 toz< 1, but the contribution of the $14.6\le \log N_{\mathrm{H}\mathrm{I}}<19$absorbers to the total metal budget of the universe atz< 1 is a quarter of that at 2.2 ≲z≲ 3.6. We show that FOGGIE cosmological zoom-in simulations have a similar evolution of [X/H] withN_Hi, which is not observed in lower-resolution simulations. In these simulations, very metal-poor absorbers with [X/H] < − 2.4 atz∼ 2–3 are tracers of inflows, while higher-metallicity absorbers are a mixture of inflows and outflows. 

Abstract We combine 126 new galaxy-Oviabsorber pairs from the CGM²survey with 123 pairs drawn from the literature to examine the simultaneous dependence of the column density of Oviabsorbers (N_OVI) on galaxy stellar mass, star-formation rate, and impact parameter. The combined sample consists of 249 galaxy-Oviabsorber pairs coveringz= 0–0.6, with host galaxy stellar massesM_*= 10^7.8–10^11.2M_⊙and galaxy-absorber impact parametersR_⊥= 0–400 proper kiloparsecs. In this work, we focus on the variation ofN_OVIwith galaxy mass and impact parameter among the star-forming galaxies in the sample. We find that the averageN_OVIwithin one virial radius of a star-forming galaxy is greatest for star-forming galaxies withM_*= 10^9.2–10¹⁰M_⊙. Star-forming galaxies withM_*between 10⁸and 10^11.2M_⊙can explain most Ovisystems with column densities greater than 10^13.5cm⁻². Sixty percent of the Ovimass associated with a star-forming galaxy is found within one virial radius, and 35% is found between one and two virial radii. In general, we find that some departure from hydrostatic equilibrium in the CGM is necessary to reproduce the observed Oviamount, galaxy mass dependence, and extent. Our measurements serve as a test set for CGM models over a broad range of host galaxy masses.