A QSO host galaxy and its Lyα emission at z = 6.43
Abstract
Host galaxies of highest redshift quasi-stellar objects (QSOs) are of interest; they provide us with a valuable opportunity to investigate physics relevant to the starburst-active galactic nuclei (AGN) connection at the earliest epoch of the Universe, with the most luminous black holes.
Here, we report an optical detection of an extended structure around a QSO at z = 6.43 in deep z'- and zr-band images of the Subaru/Suprime-Cam. Our target is CFHQS J2329-0301 (z = 6.43), the highest redshift QSO currently known. We have carefully subtracted a point spread function (PSF) constructed using nearby stars from the images. After the PSF (QSO) subtraction, a structure in the z' band extends more than 4arcsec on the sky (Re = 11 kpc), and, thus, is well resolved (16σ detection). The PSF-subtracted zr-band structure is in a similar shape to that in the z' band, but less significant with a 3σ detection. In the z' band, a radial profile of the QSO+host shows a clear excess over that of the averaged PSF in 0.8-3 arcsec radius. Since the z' band includes a Lyα emission at z = 6.43, we suggest the z' flux is a mixture of the host (continuum light) and its Lyα emission, whereas the zr-band flux is from the host. Through a SED modelling, we estimate 40 per cent of the PSF-subtracted z'-band light is from the host (continuum) and 60 per cent is from Lyα emission. The absolute magnitude of the host is M1450 = -23.9 (cf. M1450 = -26.4 for the QSO). A lower limit of the SFR(Lyα) is 1.6Msolar yr-1 with stellar mass ranging from 6.2 × 108 to 1.1 × 1010Msolar when 100 Myr of age is assumed. The detection shows that a luminous QSO is already harboured by a large, star-forming galaxy in the early Universe only after ~840 Myr after the big bang. The host may be a forming giant galaxy, co-evolving with a super-massive black hole. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. E-mail: tomo@ifa.hawaii.edu ‡ JSPS SPD Fellow.- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2009
- DOI:
- 10.1111/j.1365-2966.2009.15486.x
- arXiv:
- arXiv:0908.4079
- Bibcode:
- 2009MNRAS.400..843G
- Keywords:
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- black hole physics;
- galaxies: high-redshift;
- early Universe;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Accepted for publication in MNRAS. A higher resolution pdf is at http://ifa.hawaii.edu/~tomo/QSOhost/QSOhost_v7.pdf