2007A&A...472L..33M -
Astronomy and Astrophysics, volume 472, L33-37 (2007/9-3)
Molecular gas in QSO host galaxies at z>5.
MAIOLINO R., NERI R., BEELEN A., BERTOLDI F., CARILLI C.L., CASELLI P., COX P., MENTEN K.M., NAGAO T., OMONT A., WALMSLEY C.M., WALTER F. and WEISS A.
Abstract (from CDS):
We present observations with the IRAM Plateau de Bure Interferometer of three QSOs at z>5 aimed at detecting molecular gas in their host galaxies as traced by CO transitions. CO (5-4) is detected in
SDSS J033829.31+002156.3 at z=5.0267, placing it amongst the most distant sources detected in CO. The CO emission is unresolved with a beam size of ∼1'', implying that the molecular gas is contained within a compact region, less than ∼3kpc in radius. We infer an upper limit on the dynamical mass of the CO emitting region of ∼3x10
10M
☉/sin(i)
2. The comparison with the Black Hole mass inferred from near-IR data suggests that the BH-to-bulge mass ratio in this galaxy is significantly higher than in local galaxies. From the CO luminosity we infer a mass reservoir of molecular gas as high as M(H
2)=2.2x10
10M
☉, implying that the molecular gas accounts for a significant fraction of the dynamical mass. When compared to the star formation rate derived from the far-IR luminosity, we infer a very short gas exhaustion timescale (∼10
7years), comparable to the dynamical timescale. CO is not detected in the other two QSOs (
SDSS J083643.85+005453.3 and
SDSS J163033.90+401209.6) and upper limits are given for their molecular gas content. When combined with CO observations of other type 1 AGNs, spanning a wide redshift range (0<z<6.4), we find that the host galaxy CO luminosity (hence molecular gas content) and the AGN optical luminosity (hence BH accretion rate) are correlated, but the relation is not linear: L'
CO∝[λL
λ(4400Å)]
0.72. Moreover, at high redshifts (and especially at z>5) the CO luminosity appears to saturate. We discuss the implications of these findings in terms of black hole-galaxy co-evolution.
Abstract Copyright:
∼
Journal keyword(s):
galaxies: high-redshift - galaxies: ISM - galaxies: quasars: general - infrared: galaxies - submillimeter
Simbad objects:
6
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