How much of the extreme luminosity of IRAS F10214+4724 can be attributed to gravitational lensing?
Abstract
The galaxy IRAS F10214+4724, discovered in a spectroscopic survey of a 0.2-Jy sample by Rowan-Robinson and collaborators in 1991, is significantly more luminous than any other known galaxy. Its bolometric luminosity is 2x10^14 L_solar, which is comparable to the luminosities of the most luminous quasars. Recent observations have revealed a candidate foreground group of galaxies, which might gravitationally lense F10214+4724, thus explaining much of its luminosity. High-resolution imaging of F10214+4724 has revealed that most of its near-IR flux comes from a circularly symmetric arc; this also supports the gravitational lens interpretation. In such a scenario, F10214+4724 would be the high-redshift analogue of the ultraluminous IRAS galaxies observed locally. This work presents a simple statistical lensing model to investigate this possibility. We show that, on statistical grounds alone, the probability that F10214+4724 is a gravitational lens system with magnification 2<mu<10 is approximately 25 per cent, if nearby determinations of the luminosity function phi(L) for ultraluminous IRAS galaxies can be extrapolated to both high redshifts z and high luminosities L. If phi(L) steepens with either increasing z or increasing L, we predict a substantial increase in the probability of F10214+4724 being a lens system. Very large magnifications (mu<~20) are ruled out by this model, unless phi(L) is very steep, e.g., a power law with index alpha<-6. These results therefore suggest that F10214+4724 is indeed the most luminous galaxy known. However, if it is a lens system with mu<~2, it would not have been discovered had it not been lensed.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- November 1995
- DOI:
- 10.1093/mnras/277.2.616
- arXiv:
- arXiv:astro-ph/9506073
- Bibcode:
- 1995MNRAS.277..616T
- Keywords:
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- METHODS: STATISTICAL;
- GALAXIES: INDIVIDUAL: IRAS F10214+4724;
- GRAVITATIONAL LENSING;
- Astrophysics
- E-Print:
- 30 pages, available by at ftp://hubble.ifa.hawaii.edu/pub/nat