Host galaxies of bright high redshift quasars: Luminosities and colours - AstrophysicsReport as inadecuate

Host galaxies of bright high redshift quasars: Luminosities and colours - Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We present the results of a near-infrared imaging study of high redshiftz~3 quasars using the ESO-VLT. Our targets were selected to have luminositiesamong the highest known absolute magnitude M B <~ -28. We searched forresolved structures underlying the bright point-source nuclei by comparing theQSO images with stars located in the same fields. Two QSOs HE2348-1444 atz=2.904 and HE2355-5457 at z=2.933 are clearly resolved in K S, and withsomewhat lower significance also in H; one object is resolved only in K S. Atthese redshifts, H and K S correspond almost exactlly to rest-frame B and V,respectively, with virtually no K-correction. We also report briefly thenon-detection of some additional QSOs. The detected host galaxies are extremelyluminous with M V ~ -25. Their rest-frame B-V colours, however, are close tozero in the Vega system, indicating substantial contributions from young starsand a stellar mass-to-light ratio below 1 in solar units. Tentativelyconverting M V and B-V into rough estimates of stellar masses, we obtain valuesof M star in the range of several 10^11 M sun, placing them within thehigh-mass range of recent high-redshift galaxy surveys. We present opticalspectra and use CIV line width measurements to predict virial black holemasses, obtaining typical values of M bh ~ 5x10^9 M sun. With respect to theknown correlation between host galaxy luminosity L Vhost and M bh, ourmeasurements reach to higher luminosities and redshifts than previous studies,but are completely consistent with them. Comparing our objects with the localz~0 M bh - M bulge relation and taking also the low stellar mass-to-lightratios into account, we find tentative evidence for an excess in theM bh-M bulge mass ratio at z~3.

Author: M. Schramm 1, L. Wisotzki 1, K. Jahnke 2 1 Astrophysikalisches Institut Potsdam, 2 Max-Planck Institut für Astronomie Heidelberg


Related documents