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THE COS-HALOS SURVEY: RATIONALE, DESIGN, AND A CENSUS OF CIRCUMGALACTIC NEUTRAL HYDROGENBased on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO11598.
- Source :
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Astrophysical Journal . 11/1/2013, Vol. 777 Issue 1, p59-91. 33p. - Publication Year :
- 2013
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Abstract
- We present the design and methods of the COS-Halos survey, a systematic investigation of the gaseous halos of 44 z = 0.15-0.35 galaxies using background QSOs observed with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. This survey has yielded 39 spectra of zem ≃ 0.5 QSOs with S/N ∼10-15 per resolution element. The QSO sightlines pass within 150 physical kpc of the galaxies, which span early and late types over stellar mass log M*/M☼ = 9.5-11.5. We find that the circumgalactic medium exhibits strong H I, averaging ≃ 1 Å in Lyα equivalent width out to 150 kpc, with 100% covering fraction for star-forming galaxies and 75% covering for passive galaxies. We find good agreement in column densities between this survey and previous studies over similar range of impact parameter. There is weak evidence for a difference between early- and late-type galaxies in the strength and distribution of H I. Kinematics indicate that the detected material is bound to the host galaxy, such that ≳ 90% of the detected column density is confined within ±200 km s–1 of the galaxies. This material generally exists well below the halo virial temperatures at T ≲ 105 K. We evaluate a number of possible origin scenarios for the detected material, and in the end favor a simple model in which the bulk of the detected H I arises in a bound, cool, low-density photoionized diffuse medium that is generic to all L* galaxies and may harbor a total gaseous mass comparable to galactic stellar masses. [ABSTRACT FROM AUTHOR]
- Subjects :
- *GALACTIC halos
*HYDROGEN
*INTERSTELLAR medium
*STELLAR mass
*ASTROPHYSICS research
Subjects
Details
- Language :
- English
- ISSN :
- 0004637X
- Volume :
- 777
- Issue :
- 1
- Database :
- Academic Search Index
- Journal :
- Astrophysical Journal
- Publication Type :
- Academic Journal
- Accession number :
- 94288697
- Full Text :
- https://doi.org/10.1088/0004-637X/777/1/59