The CGM² Survey: Circumgalactic O vi from Dwarf to Massive Star-forming Galaxies

Abstract

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.

The longstanding galaxy missing-baryon problem is solved by a large reservoir of hot gas permeating their halos

“…4, for NOVII and NVI, respectively. We find NOVII=(4.1±3.4)×10 16 cm -2 , NNVI=(3.1±1.5)×10 15 cm -2 , and a common bO,N=33-75 km s -1 .…”

“…4; see Methods for details). We find NOVII=(4.1±3.4)×10 16 cm -2 , NNVI=(3.1±1.5)×10 15 cm -2 , and bO,N=33-75 km s -1 . By combining our measured OVII and NVI column densities with the average X-ray-halo OVI column density measured in the FUV (column 7 of last row of ED Table 1), we infer the temperature and hydrogenequivalent column density of the hot gas permeating the X-ray-halo associated to LLS absorbers (Fig.…”

“…Observationally, the presence of this hot phase is currently only hinted through Sunyaev-Zeldovich [21] and low-resolution X-ray [22] measurements of the surroundings of local L* galaxy or pioneering X-ray absorption [23] studies (see below), and more ubiquitously through absorption by moderately-ionized ions of oxygen (e.g. [13,[16][17][18]) and neon (e.g. [19]).…”

“…Pioneering single-target X-ray spectroscopic studies of these transitions from the halos of optimally-selected LLSs have indeed been recently performed [23] , but are hampered by the limited resolution and throughput of current X-ray spectrometers, and did not produce conclusive results [23] . Detailed surveys of galaxyhigh-ionization X-ray-absorber associations, comparable to low-or moderate-ionization FUV studies like the COS-Halos Survey [12] or the CGM 2 Survey [16] , will have to wait for the next generation of high-throughput X-ray spectrometers (e.g. the Athena-XIFU [24] or Arcus [25] ).…”

The scaling relation between galaxy luminosity and WHIM density from EAGLE simulations with application to SDSS data

“…FUV studies do provide evidence that at least a portion of these O VI absorption lines are associated with the galaxies themselves (e.g. Stocke et al 2006 ;Tchern yshyo v et al 2022 ). It is therefore possible that the warm WHIM (i.e.…”