1 / 17

Cool Halo Gas in a Cosmological Context

Cool Halo Gas in a Cosmological Context. Kyle Stewart “Team Irvine” UC Santa Cruz Galaxy Formation Workshop 8-20-09. Collaborators: James Bullock, Betsy Barton (UCI) Tobias Kaufman, Lucio Mayer (UZH) Jürg Diemand, Piero Madau (UCSC) James Wadsley (McMaster), Ari Maller (NYCCT).

otto
Download Presentation

Cool Halo Gas in a Cosmological Context

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cool Halo Gas in a Cosmological Context Kyle Stewart “Team Irvine” UC Santa Cruz Galaxy Formation Workshop 8-20-09 Collaborators: James Bullock, Betsy Barton (UCI) Tobias Kaufman, Lucio Mayer (UZH) Jürg Diemand, Piero Madau (UCSC) James Wadsley (McMaster), Ari Maller (NYCCT)

  2. Outline • Theoretical Motivations • Baryonic content of DM halos • Gas accretion via gas-rich mergers • Observing Cool Halo Gas • Unresolved / open questions • The Simulation: VL2 + GASOLINE • Covering Fraction • Kinematics: Halo Gas vs. Galaxy

  3. Motivations • How do galaxies acquire their cool gas? • Cold flows? Cloud Fragmentation? (e.g. Keres et al. ‘09, Dekel & Birnboim ‘06, Maller & Bullock ’04, most of Tuesday’s talks…) • Gas rich mergers? • Stewart et al. 09

  4. Small halos have a lot of gas and few stars (especially at z~1) Stewart 2009 Abundance matching (Conroy & Wechsler ‘09) + baryonic TF

  5. Gas-rich mergers & galaxy assembly Stewart et al. 2009 ~30% of an L* galaxy’s baryons accreted in Major, gas-rich mergers over it’s history (since z=2). ~20% of bright galaxies at z~1 have had a Major, gas-rich merger in last Gyr (not based on this plot)

  6. Motivations • How do galaxy acquire their cool gas? • How can we test ideas? • Absorption-systems as probes of cool halo gas…

  7. Observing Gas Around Galaxies: QSO (Mg II) D ~ 100 kpc (or less) Image from Tripp & Bowen (2005) 2) Cloud vs. Galaxy Kinematics • Covering Fraction

  8. Observing Gas Around Galaxies: • Covering Fraction Mg II Cf ~20-80% 2) Cloud vs. Galaxy Kinematics But what ARE they? Spherical halo gas? Cold Filaments? Pressure-confined gas clouds? Outflowing winds? Tidal Streams? e.g. Tripp & Bowen ’05; Tinker & Chen ‘08; Kackprzak et al. '08

  9. Observing Gas Around Galaxies: Kacprzak et al. ‘09 (submitted) • Covering Fraction 2) Cloud vs. Galaxy Kinematics 7/10 Mg II absorbers show velocities that co-rotate with galaxy

  10. Galaxies Probing Galaxies Rubin et al. ‘09 z~0.5 z~0.7 Keck/LRIS absorption spectrum Spatially-extended complex of cool clouds at d>17kpc from galaxy (with high velocity width) Cool gas ejected from host galaxy during past merger?

  11. Our Simulation: Log rHI [Msun/pc3 ]= [-8, -1] + Diemand et al. ‘08 Wadsley et al. ‘04 VL2 (initial conditions) GASOLINE (sph code) Some stats: WMAP3 cosmo: W0=0.24, L=0.76, h=0.73, σ8=0.77, Wb=0.042 mDM, mgas, mstar ~3e5, 4e5, 1e5 Msun, Np~4 million. Sph smooth len: 332 pc. Final halo mass Mvir~2.e12 Msun ‘Blast-wave’ feedback of Stinson et al. ‘06; Haardt & Madau ‘96 UV field; NOTE: no strong blow-out winds Log rstars [Msun/pc3 ] = [-7, 1]

  12. Results: Covering Fraction Router ~ 50 kpc (comoving) Ngrid ~ 1000 Rinner ~ 5 kpc (comoving) LOS “covered” if N(HI) >1016,18,20 atoms/cm2

  13. Results: Covering Fraction (averaged over 3 projections) Fragmented Flows + Mergers Covering Fraction Depends on Recent Gas Accretion! Cold flows (and mergers) Note: VL2 chosen to be quiescent at late times

  14. Gas and Galaxy Kinematics: LOS velocity [-250 to +250 km/s] Log rHI = [-7, 1]

  15. Gas and Galaxy Kinematics: LOS velocity [-250 to +250 km/s] Log rHI = [-7, 1]

  16. Summary: • High-res SPH simulation of VL2 halo with gas + stars • Extended cool halo gas betrays a complex assembly history: • Gas-rich & star-poor mergers are common and responsible for much of the halo gas (especially at z<2) • These mergers would be invisible to pair-counts at fixed luminosity • Cool halo gas tends to co-rotate with the galaxy, as indicated by observations. This gas includes clouds, streams, and other complex structures – the gas that will build the galaxy itself. • Covering Fraction for cool gas depends on recent gas accretion: smooth (or fragmented) filaments, mergers, etc. • Covering fraction in VL2 remains high well past the time associated with the canonical cold flow epoch, as a result of mergers and infalling fragments.

  17. Extra Slides:

More Related