We present a spectroscopic catalog of the 1,564 brightest (J < 9) M dwarf candidates in the northern sky, as selected from the SUPERBLINK proper motion catalog. Observations confirm 1,408 of the candidates to be late-K and M dwarfs with spectral subtypes K7-M6. From the low (µ >40 mas yr −1 ) proper motion limit and high level of completeness of the SUPERBLINK catalog in that magnitude range, we estimate that our spectroscopic census most likely includes > 90% of all existing, northern-sky M dwarfs with apparent magnitude J < 9. Only 682 stars in our sample are listed in the Third Catalog of Nearby Stars (CNS3); most others are relative unknowns and have spectroscopic data presented here for the first time. Spectral subtypes are assigned based on spectral index measurements of CaH and TiO molecular bands; a comparison of spectra from the same stars obtained at different observatories however reveals that spectral band index measurements are dependent on spectral resolution, spectrophotometric calibration, and other instrumental factors. As a result, we find that a consistent classification scheme requires that spectral indices be calibrated and corrected for each observatory/instrument used. After systematic corrections and a recalibration of the subtype-index relationships for the CaH2, CaH3, TiO5, and TiO6 spectral indices, we find that we can consistently and reliably classify all our stars to a half-subtype precision. The use of corrected spectral indices further requires us to recalibrate the ζ parameter, a metallicity indicator based on the ratio of TiO and CaH optical bandheads. However, we find that our ζ values are not sensistive enough to diagnose metallicity variations in dwarfs of subtypes M2 and earlier (±0.5dex accuracy) and are only marginally useful at later M3-M5 subtypes (±0.2dex accuracy). Fits of our spectra to the Phoenix atmospheric model grid are used to estimate effective temperatures. These suggest the existence of a plateau in the M1-M3 subtype range, in agreement with model fits of infrared spectra but at odds with photometric determinations of T e f f . Existing geometric parallax measurements are extracted from the literature for 624 stars, and are used to determine spectroscopic and photometric distances for all the other stars. Active dwarfs are identified from measurements of Hα equivalent widths, and we find a strong correlation between Hα emission in M dwarfs and detected X-ray emission from ROSAT and/or a large UV excess in the GALEX point source catalog. We combine proper motion data and photometric distances to evaluate the (U,V,W) distribution in velocity space, which is found to correlate tighly with the velocity distribution of G dwarfs in the Solar Neighborhood. However, active stars show a smaller dispersion in their space velocities, which is consistent with those stars being younger on average. Our catalog will be most useful to guide the selection of the best M dwarf targets for exoplanet searches, in particular those using high-precision radial velocity measurements.

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.

We present initial results from the Cosmic Origins Spectrograph (COS) and Gemini Mapping the Circumgalactic Medium (CGMCGM ≡ CGM2) survey. The CGM2 survey consists of 1689 galaxies, all with high-quality Gemini-GMOS spectra, within 1 Mpc of 22 z ≲ 1 quasars, all with a signal-to-noise ratio of ∼10 Hubble Space Telescope/COS G130M+G160M spectra. For 572 of these galaxies with stellar masses 107 M ⊙ < M ⋆ < 1011 M ⊙ and z ≲ 0.5, we show that the H i covering fraction above a threshold of N HI > 1014cm−2 is ≳0.5 within 1.5 virial radii (R vir ∼ R 200m). We examine the H i kinematics and find that the majority of absorption lies within ±250 km s−1 of the galaxy systemic velocity. We examine H i covering fractions over a range of impact parameters to infer a characteristic size of the CGM, , as a function of galaxy mass. is the impact parameter at which the probability of observing an absorber with N HI >1014 cm−2 is >50%. In this framework, the radial extent of the CGM of M ⋆ > 109.9 M ⊙ galaxies is kpc or . Intermediate-mass galaxies with 109.2 < M ⋆/M ⊙ < 109.9 have an extent of kpc or . Low-mass galaxies, M ⋆ < 109.2 M ⊙, show a smaller physical scale of kpc and extend to . Our analysis suggests that using R vir as a proxy for the characteristic radius of the CGM likely underestimates its extent.

We combine 126 new galaxy-O vi absorber pairs from the CGM2 survey with 123 pairs drawn from the literature to examine the simultaneous dependence of the column density of O vi absorbers (N O VI) on galaxy stellar mass, star-formation rate, and impact parameter. The combined sample consists of 249 galaxy-O vi absorber pairs covering z = 0–0.6, with host galaxy stellar masses M * = 107.8–1011.2 M ⊙ and galaxy-absorber impact parameters R ⊥ = 0–400 proper kiloparsecs. In this work, we focus on the variation of N O VI with galaxy mass and impact parameter among the star-forming galaxies in the sample. We find that the average N O VI within one virial radius of a star-forming galaxy is greatest for star-forming galaxies with M * = 109.2–1010 M ⊙. Star-forming galaxies with M * between 108 and 1011.2 M ⊙ can explain most O vi systems with column densities greater than 1013.5 cm−2. Sixty percent of the O vi mass 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 O vi amount, galaxy mass dependence, and extent. Our measurements serve as a test set for CGM models over a broad range of host galaxy masses.

Retinal vein occlusions (RVOs), including central retinal vein occlusions (CRVOs) and branch retinal vein occlusions (BRVOs), are a common cause of morbidity in elderly patients. We present the case of a healthy 74-year-old female patient who initially presented with blurry vision in her left eye in the setting of a symptomatic COVID-19 infection. She was diagnosed with a branch retinal vein occlusion that did not immediately require treatment. Three months later, she again presented with worsening vision and was found to have cystoid macular edema (CME) secondary to the vein occlusion, thus was treated with an intravitreal dexamethasone implant. This case serves to highlight the growing evidence of increased thromboembolic risk associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the possible correlation of COVID-19 infections with ocular pathology, including retinal vein occlusions.