OBSERVING THE END OF COLD FLOW ACCRETION USING HALO ABSORPTION SYSTEMS

Journal Article · Fri Jul 01 04:00:00 EDT 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/735/1/L1· OSTI ID:21562580

Stewart, Kyle R ^[1]; Kaufmann, Tobias ^[2]; Bullock, James S; Barton, Elizabeth J ^[3]; Maller, Ariyeh H ^[4]; Diemand, Juerg ^[5]; Wadsley, James ^[6]

---

1. Jet Propulsion Laboratory, Pasadena, CA 91109 (United States)
2. Institute for Astronomy, ETH Zurich, CH-8093 Zurich (Switzerland)
3. Center for Cosmology, Department of Physics and Astronomy, The University of California at Irvine, Irvine, CA 92697 (United States)
4. Department of Physics, New York City College of Technology, 300 Jay St., Brooklyn, NY 11201 (United States)
5. Institute for Theoretical Physics, University of Zurich, 8057 Zurich (Switzerland)
6. Department of Physics and Astronomy, McMaster University, Main Street West, Hamilton L85 4M1 (Canada)

We use cosmological smoothed particle hydrodynamic simulations to study the cool, accreted gas in two Milky Way size galaxies through cosmic time to z = 0. We find that gas from mergers and cold flow accretion results in significant amounts of cool gas in galaxy halos. This cool circum-galactic component drops precipitously once the galaxies cross the critical mass to form stable shocks, M{sub vir} = M{sub sh} {approx} 10{sup 12} M{sub sun}. Before reaching M{sub sh}, the galaxies experience cold mode accretion (T < 10{sup 5} K) and show moderately high covering fractions in accreted gas: f{sub c} {approx} 30%-50% for R < 50 comoving kpc and N{sub Hi}>10{sup 16} cm{sup -2}. These values are considerably lower than observed covering fractions, suggesting that outflowing gas (not included here) is important in simulating galaxies with realistic gaseous halos. Within {approx}500 Myr of crossing the M{sub sh} threshold, each galaxy transitions to hot mode gas accretion, and f{sub c} drops to {approx}5%. The sharp transition in covering fraction is primarily a function of halo mass, not redshift. This signature should be detectable in absorption system studies that target galaxies of varying host mass, and may provide a direct observational tracer of the transition from cold flow accretion to hot mode accretion in galaxies.

• OSTI ID: 21562580
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 735; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
EVOLUTION
FLUID MECHANICS
GALACTIC EVOLUTION
GALAXIES
HYDRODYNAMICS
MECHANICS
MILKY WAY
SIMULATION