Characterizing the abundance, properties, and kinematics of the cool circumgalactic medium of galaxies in absorption with SDSS DR16

Abstract

In order to study the circumgalactic medium (CGM) of galaxies we develop an automated pipeline to estimate the optical continuum of quasars and detect intervening metal absorption line systems with a matched kernel convolution technique and adaptive S/N criteria. We process ∼ one million quasars in the latest Data Release 16 (DR16) of the Sloan Digital Sky Survey (SDSS) and compile a large sample of ∼ 160,000 Mg absorbers, together with ∼ 70,000 Fe systems, in the redshift range 0.35 < 𝑧 𝑎𝑏𝑠 < 2.3. Combining these with the SDSS DR16 spectroscopy of ∼ 1.1 million luminous red galaxies (LRGs) and ∼ 200, 000 emission line galaxies (ELGs), we investigate the nature of cold gas absorption at 0.5 < 𝑧 < 1. These large samples allow us to characterize the scale dependence of Mg with greater accuracy than in previous work. We find that there is a strong enhancement of Mg absorption within ∼ 50 kpc of ELGs, and the covering fraction within 0.5𝑟 vir of ELGs is 2-5 times higher than for LRGs. Beyond 50 kpc, there is a sharp decline in Mg for both kinds of galaxies, indicating a transition to the regime where the CGM is tightly linked with the dark matter halo. The Mg covering fraction correlates strongly with stellar mass for LRGs, but weakly for ELGs, where covering fractions increase with star formation rate. Our analysis implies that cool circumgalactic gas has a different physical origin for star forming versus quiescent galaxies.

A Big Ring on the sky

“…(1) Each of the visually-identified BR+filament absorbers was confirmed visually in the corresponding spectra, establishing that JCAP07(2024)055 20 and the other similar figures that follow it. The rest-frame equivalent widths (EW) and their associated uncertainties (σ EW , taken from the Mg II database of [3], are for the λ 2796 component of the Mg II doublet; the units are Å. Note that the EW for point 12 is likely to be enhanced by the superimposed λ 2803 component from point 11.…”

“…Here, in figure 25, we show a corresponding figure but with the points now colour-coded according to the rest-frame equivalent widths (in Å) of the λ 2796 component of the Mg II doublet. The equivalent widths and their uncertainties, both taken from the Mg II database of [3], are tabulated in table 5. In figure 25 there is no obvious pattern for the lower equivalent widths, but we note that the higher equivalent widths tend to be concentrated on the r.h.s.…”

“…We continue to make use of the method of intervening Mg II absorbers in the spectra of quasars to trace faint matter at intermediate redshifts [1,2]. The Mg II method relies on both the spectroscopic measurement of luminous, high redshift quasars from the Sloan Digital Sky Survey (SDSS), and the highly accurate, spectroscopic redshifts of the intervening Mg II absorption doublets present in the quasar spectra, documented by independent authors [3,4]. The intervening Mg II absorption doublet indicates the presence of galaxies and galaxy clusters [5][6][7].…”

“…During the discovery of the Giant Arc (GA) [2] (hereafter Lopez22), the SDSS Data Release 16 quasar database (DR16Q) became available [23]. Then, independent authors created the most up-to-date Mg II database from the DR16Q quasars [3] (hereafter Anand21). Following the discovery of the GA, made using the older Mg II database from [4] (hereafter Z&M, also the corresponding DR7QSO and DR12Q quasar catalogues from [24,25]), we are now in a position to continue LSS investigations with the new DR16Q database and corresponding DR16Q Mg II database.…”

“…of the figure indicates the rest-frame equivalent widths (in Å) of the λ 2796 component of the absorbers associated by the colours, and the small numbers paired with each data point indicate their unique ID number. The equivalent widths are taken from the Mg II database of[3].…”