Does Gas Cool From the Hot Phase? (onto galaxies). Hot Gas in/around Ellipticals: Lessons Learned Hot Gas Environment of the Milky Way and Local Group: Limits on Accretion Missing Baryons in Galaxies and Galaxy Groups. The MPA/ESO/MPE/USM 2007 Joint Astronomy Conference
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Hot Gas in/around Ellipticals: Lessons Learned
Hot Gas Environment of the Milky Way and Local Group: Limits on Accretion
Missing Baryons in Galaxies and Galaxy Groups
The MPA/ESO/MPE/USM 2007 Joint Astronomy Conference
Gas Accretion and Star Formation in Galaxies
Joel Bregman (Univ. of Michigan)
This is known as
The last Cooling Flow Meeting
X-Ray Observations (XMM-Newton)
Fe is about Solar ([Fe] = 0)
[O/Fe] = -0.3
Metallicity like stars
Not like Cluster/group [Fe] = -0.5
Gas from Stellar Mass Loss
Not dominated by accretion from cluster/group
XMM RGS spectrum of NGC 4636 (Xu et al. 2003)
Far Ultraviolet Spectroscopic Explorer (RIP)
OVI is detected in about 40% of galaxies
Some cooling gas at 3x105 K
Cooling rates of 0.1-0.5 Msun/yr
In central region; not distributed.
Bregman et al. (2005)
Chandra ACIS-S; 108 ksec of cleaned data
Point sources removed; smoothed
Hot gas easily seen to a height of 4.5 kpc from disk (1.6’) Fainter emission goes to a height of 9 kpc (3’)
Extent along disk similar to Halpha, FIR
Thermal emission; 4E39 erg/s
Mdot = 0.1 Msun/yr
Oosterloo et al. 2007; NGC 891 HI
Z = 0.1 Solar
N = 1019 cm-2
OVII, OVIII have X-ray resonance lines; best sensitivity
Detect Hot Gas by X-ray Absorption Lines
Group simulation like the Local Group (Moore) shows elongation of matter .
Column enhancement along major axis ~2-3x perpendicular to axis
26 Target AGNs; mean EW = 22 mÅ; 17 with rms < 10 mÅ
These are the 4 best.
Bregman and Lloyd-Davies (2007; arXiv:0707.1699)
An AGN toward M31 (long axis of Local Group)
One of the smallest columns, not one of the largest
The OVII data don’t fit a Local Group Model
Central Line Velocities close to MW
Supports a Galatic Halo Origin (10-100 kpc)
Gas Mass of 108 – 1010 Msun
Compare to NGC 5746 (Rasmussen & Ponman 2004): 109 Msun for similar metallicity
This would reveal the fraction of X-ray emission beyond these clouds
Help determine the hot gas component of the Local Group
JNB, Birgit Otte, J. Irwin, M. Putman, E. Lloyd-Davies, C. Breuns (2007)
We see a brightening, not a shadow toward both clouds.
Clouds are interacting with a hot medium within 100 kpc of the MW.
Density/Temp of the hot medium is model-dependent.