ALMACAL V: absorption-selected galaxies with evidence for excited ISMs
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ALMACAL V : absorption-selected galaxies with evidence for excited ISMs. / Klitsch, A.; Zwaan, M. A.; Péroux, C.; Smail, I.; Oteo, I.; Popping, G.; Swinbank, A. M.; Ivison, R. J.; Biggs, A. D.
In: Royal Astronomical Society. Monthly Notices, Vol. 482, 01.2019, p. L65-L69.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - ALMACAL V
T2 - absorption-selected galaxies with evidence for excited ISMs
AU - Klitsch, A.
AU - Zwaan, M. A.
AU - Péroux, C.
AU - Smail, I.
AU - Oteo, I.
AU - Popping, G.
AU - Swinbank, A. M.
AU - Ivison, R. J.
AU - Biggs, A. D.
PY - 2019/1
Y1 - 2019/1
N2 - Gas-rich galaxies are selected efficiently via quasar absorption lines. Recently, a new perspective on such absorption-selected systems has opened up by studying the molecular gas content of absorber host galaxies using ALMA CO emission line observations. Here, we present an analysis of multiple CO transitions (L^' }_CO ̃ 10^9 K km s-1) in two z ̃ 0.5 galaxies associated with one Ly α absorber towards J0238+1636. The CO spectral line energy distributions (CO SLEDs) of these galaxies appear distinct from that of typical star-forming galaxies at similar redshifts and is comparable with that of luminous infrared galaxies or active galactic nucleus (AGN). Indeed, these galaxies are associated with optically identified AGN activity. We infer that the CO line ratios and the αCO conversion factor differ from the Galactic values. Our findings suggest that at least a fraction of absorption-selected systems shows interstellar medium conditions deviating from those of normal star-forming galaxies. For a robust molecular gas mass calculation, it is therefore important to construct the CO SLED. Absorption line selection identifies systems with widely distributed gas, which may preferentially select interacting galaxies, which in turn will have more excited CO SLEDs than isolated galaxies. Furthermore, we raise the question whether quasar absorbers preferentially trace galaxy overdensities....
AB - Gas-rich galaxies are selected efficiently via quasar absorption lines. Recently, a new perspective on such absorption-selected systems has opened up by studying the molecular gas content of absorber host galaxies using ALMA CO emission line observations. Here, we present an analysis of multiple CO transitions (L^' }_CO ̃ 10^9 K km s-1) in two z ̃ 0.5 galaxies associated with one Ly α absorber towards J0238+1636. The CO spectral line energy distributions (CO SLEDs) of these galaxies appear distinct from that of typical star-forming galaxies at similar redshifts and is comparable with that of luminous infrared galaxies or active galactic nucleus (AGN). Indeed, these galaxies are associated with optically identified AGN activity. We infer that the CO line ratios and the αCO conversion factor differ from the Galactic values. Our findings suggest that at least a fraction of absorption-selected systems shows interstellar medium conditions deviating from those of normal star-forming galaxies. For a robust molecular gas mass calculation, it is therefore important to construct the CO SLED. Absorption line selection identifies systems with widely distributed gas, which may preferentially select interacting galaxies, which in turn will have more excited CO SLEDs than isolated galaxies. Furthermore, we raise the question whether quasar absorbers preferentially trace galaxy overdensities....
U2 - 10.1093/mnrasl/sly187
DO - 10.1093/mnrasl/sly187
M3 - Journal article
VL - 482
SP - L65-L69
JO - Royal Astronomical Society. Monthly Notices
JF - Royal Astronomical Society. Monthly Notices
SN - 0035-8711
ER -
ID: 280890636