Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-line Spectroscopy
Abstract
The circumgalactic medium (CGM) of late-type galaxies is characterized using UV spectroscopy of 11 targeted QSO/galaxy pairs at z <= 0.02 with the Hubble Space Telescope Cosmic Origins Spectrograph (COS) and ~60 serendipitous absorber/galaxy pairs at z <= 0.2 with the Space Telescope Imaging Spectrograph. CGM warm cloud properties are derived, including volume filling factors of 3%-5%, cloud sizes of 0.1-30 kpc, masses of 10-108 M ⊙, and metallicities of ~0.1-1 Z ⊙. Almost all warm CGM clouds within 0.5 R vir are metal-bearing and many have velocities consistent with being bound, "galactic fountain" clouds. For galaxies with L >~ 0.1 L*, the total mass in these warm CGM clouds approaches 1010 M ⊙, ~10%-15% of the total baryons in massive spirals and comparable to the baryons in their parent galaxy disks. This leaves >~ 50% of massive spiral-galaxy baryons "missing." Dwarfs (<0.1 L*) have smaller area covering factors and warm CGM masses (<=5% baryon fraction), suggesting that many of their warm clouds escape. Constant warm cloud internal pressures as a function of impact parameter (P/k ~ 10 cm-3 K) support the inference that previous COS detections of broad, shallow O VI and Lyα absorptions are of an extensive (~400-600 kpc), hot (T ≈ 106 K), intra-cloud gas which is very massive (>=1011 M ⊙). While the warm CGM clouds cannot account for all the "missing baryons" in spirals, the hot intra-group gas can, and could account for ~20% of the cosmic baryon census at z ~ 0 if this hot gas is ubiquitous among spiral groups.
Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2013
- DOI:
- 10.1088/0004-637X/763/2/148
- arXiv:
- arXiv:1212.5658
- Bibcode:
- 2013ApJ...763..148S
- Keywords:
-
- galaxies: dwarf;
- galaxies: groups: general;
- galaxies: halos;
- galaxies: spiral;
- intergalactic medium;
- quasars: absorption lines;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- 34 pages, 14 figures, 8 tables