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The Structure and Kinematics of the Circum-Galactic Medium from Far-UV Spectra of z~2-3 Galaxies | | C. C. Steidel
; D. K. Erb
; A. E. Shapley
; M. Pettini
; N. A. Reddy
; M. Bogosavljević
; G. C. Rudie
; O. Rakic
; | | Date: |
2 Mar 2010 | | Abstract: | We present new results on the kinematics and spatial distribution of
metal-enriched gas within 125 kpc (physical) of Lyman Break galaxies at
redshifts z~2-3. In particular, we demonstrate how rest-UV galaxy spectra can
be used to obtain key spatial and spectral information more efficiently than
possible with QSO sightlines. After recalibrating the measurement of galaxy
systemic redshifts from their UV spectra, we investigate the kinematics of
galaxy-scale outflows via the strong interstellar (IS) absorption and Lya
emission lines (when present), as well as their dependence on other physical
properties of the galaxies. We construct a sample of 512 close (1-15 arcsec)
angular pairs of z~2-3 LBGs in which the spectra background galaxies probe the
circumgalactic gas surrrounding those in the foreground. The close pairs,
together with spectra of the foreground galaxies themselves, sample
galactocentric impact parameters b=0-125 kpc (physical) at <z>=2.2. The
ensemble provides a spatial map of cool gas as a function of galactocentric
distance for a well-characterized population of galaxies. We propose a simple
model that simultaneously matches the kinematics, depth, and profile shape of
IS absorption and Lya emission lines, as well as the observed variation of
absorption line strength (of HI, CII, CIV, SiII, SiIV) versus galactocentric
impact parameter. We discuss the results of the observations in the context of
"cold accretion", in which cool gas accretes via filamentary streams directly
onto the central regions of galaxies. At present, we find little observational
support for cool infalling material, whereas evidence supporting the
large-scale effects of outflows is strong. Reconciling theory and observation
on the subject of gas flows into and out of forming galaxies seems necessary. | | Source: | arXiv, 1003.0679 | | Services: | Forum | Review | PDF | Favorites | |
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