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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."]} 

Classification is a general tool of science; it is used to sort and categorize biological organisms, chemical elements, astronomical objects, and many other things. In scientific classification, taxonomy often reflects shared physical properties that, in turn, may indicate shared origins and/or evolution. A “hands-on” galaxy-classification activity developed and implemented by Professional Development Program (PDP) participants, for a high-school summer STEM enrichment program, has been adopted for various age groups and venues, from young (K–3) to college students. We detail the basic tools required, outline the general activity, and describe the modifications to the activity based on learners’ ages and learning objectives. We describe the facilitation strategies learned through PDP training and used when implementing the activity, including prompts to motivate the students. We also discuss how we connected the classification process to astronomy and science more broadly during the concluding remarks. 

Abstract The circumgalactic medium (CGM) plays a vital role in the formation and evolution of galaxies, acting as a lifeline between galaxies and the surrounding intergalactic medium. In this study, we leverage a unique sample of quasar pairs to investigate the properties of the CGM with absorption line tomography. We present a new sample of medium-resolution Keck/ESI, Magellan/MagE, and VLT/XSHOOTER spectra of 29 quasar pairs at redshift 2 <z< 3. We supplement the sample with additional spectra of 32 pairs from the literature, creating a catalog of 61 quasar pairs with angular separations between 1.″7 and 132.″9 and projected physical separations (r_⊥) between 14 kpc and 887 kpc. We construct a catalog of 906 metal-line absorption doublets of Civ(λλ1548, 1550) with equivalent widths ranging from 6 m Å ≤W_r,1550≤ 2053 m Å. The best-fit linear model to the log-space equivalent width frequency distribution ( $\log f\left(W_r\right)=m\log \left(W_r\right)+b$) of the sample yields coefficients ofm= −1.44 ± 0.16 andb= −0.43 ± 0.16. To constrain the projected extent of Civ, we calculate the transverse autocorrelation function. The flattening of the autocorrelation function at lowr_⊥provides a lower limit for the coherence length of the metal enriched CGM—on the order of 200h⁻¹comoving kpc. This physical size constraint allows us to refine our understanding of the metals in the CGM, where the extent of Civin the CGM depends on gas flows, feedback, timescale of metal injection and mixing, and the mass of the host galaxies. 

Abstract We use medium-resolution Keck/Echellette Spectrograph and Imager spectroscopy of bright quasars to study cool gas traced by Caiiλλ3934, 3969 and Naiλλ5891, 5897 absorption in the interstellar/circumgalactic media of 21 foreground star-forming galaxies at redshifts 0.03 <z< 0.20 with stellar masses 7.4 ≤ logM_*/M_⊙≤ 10.6. The quasar–galaxy pairs were drawn from a unique sample of Sloan Digital Sky Survey quasar spectra with intervening nebular emission, and thus have exceptionally close impact parameters (R_⊥< 13 kpc). The strength of this line emission implies that the galaxies’ star formation rates (SFRs) span a broad range, with several lying well above the star-forming sequence. We use Voigt profile modeling to derive column densities and component velocities for each absorber, finding that column densitiesN(Caii) > 10^12.5cm⁻²(N(Nai) > 10^12.0cm⁻²) occur with an incidencef_C(Caii) = 0.63^+0.10_−0.11(f_C(Nai) = 0.57^+0.10_−0.11). We find no evidence for a dependence off_Cor the rest-frame equivalent widthsW_r(CaiiK) orW_r(Nai5891) onR_⊥orM_*. Instead,W_r(CaiiK) is correlated with local SFR at >3σsignificance, suggesting that Caiitraces star formation-driven outflows. While most of the absorbers have velocities within ±50 km s⁻¹of the host redshift, their velocity widths (characterized by Δv₉₀) are universally 30–177 km s⁻¹larger than that implied by tilted-ring modeling of the velocities of interstellar material. These kinematics must trace galactic fountain flows and demonstrate that they persist atR_⊥> 5 kpc. Finally, we assess the relationship between dust reddening andW_r(CaiiK) (W_r(Nai5891)), finding that 33% (24%) of the absorbers are inconsistent with the best-fit Milky WayE(B−V)-W_rrelations at >3σsignificance. 

Abstract We present spatially resolved spectroscopy from the Keck Cosmic Web Imager (KCWI) of a star-forming galaxy at z = 0.6942, which shows emission from the Mg ii λ λ 2796, 2803 doublet in the circumgalactic medium (CGM) extending ∼37 kpc at 3 σ significance in individual spaxels (1 σ detection limit 4.8 × 10 −19 erg s −1 cm −2 arcsec −2 ). The target galaxy, selected from a near-UV spectroscopic survey of Mg ii line profiles at 0.3 < z < 1.4, has a stellar mass log ( M * / M ⊙ ) = 9.9, a star formation rate of 50 M ⊙ yr −1 , and a morphology indicative of a merger. After deconvolution with the seeing, we obtain 5 σ detections of Mg ii line emission extending for ∼31 kpc measured in 7-spaxel (1.1 arcsec 2 ) apertures. Spaxels covering the galaxy stellar regions show clear P Cygni−like emission/absorption profiles, with the blueshifted absorption extending to relative velocities of v = −800 km s −1 ; however, the P Cygni profiles give way to pure emission at large radii from the central galaxy. We have performed 3D radiative transfer modeling to infer the geometry and velocity and density profiles of the outflowing gas. Our observations are most consistent with an isotropic outflow rather than biconical wind models with half-opening angles ϕ ≤ 80°. Furthermore, our modeling suggests that a wind velocity profile that decreases with radius is necessary to reproduce the velocity widths and strengths of Mg ii line emission profiles at large circumgalactic radii. The extent of the Mg ii emission we measure directly is further corroborated by our modeling, where we rule out outflow models with extent <30 kpc. 

Abstract This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys.