The apparently normal galaxy hosts for two luminous quasars

John N. Bahcall, Sofia Kirhakos, Donald P. Schneider

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HST images (with WFPC2) of PHL 909 (z = 0.171) and PG 0052 + 251 (z = 0.155) show that these luminous radio-quiet quasars each occur in an apparently normal host galaxy. The host galaxy of PHL 909 is an elliptical galaxy (∼E4), and the host of PG 0052 + 251 is a spiral (∼Sb). Both host galaxies are several tenths of a magnitude brighter than L*, the characteristic Schechter luminosity of field galaxies. The images of PHL 909 and PG 0052 + 251, when compared with HST images of other objects in our sample of 20 luminous, small-redshift (z ≤ 0.30) quasars, show that luminous quasars occur in a variety of environments. The local environments of the luminous quasars range from luminous ellipticals, to apparently normal host galaxies, to complex systems of interacting components, to faint (and as yet undetected) hosts. The bright H II regions of the host galaxy of PG 0052 + 251 provide an opportunity to measure directly the metallicity of the host of a luminous quasar, to establish an upper limit to the mass of the nuclear AGN (i.e., the putative black hole source), and to test stringently the cosmological hypothesis that the galaxy and the quasar are both at the distance indicated by the quasar redshift. The moderately luminous host galaxies of PHL 909 and PG 0052 + 251 are obvious on the HST images. Normalizing the limits of detectability using short exposures in which the host galaxies of PHL 909 and PG 0052 + 251 are easily observed, we estimate that we could have detected similar host galaxies as faint as 0.5 magnitudes less than L* in the longer exposure HST images that have not yet shown host galaxies. The details of the PSF subtraction are unimportant for the determination of the host galaxy morphologies and luminosities; the major and minor axes measured by subtracting very different stellar PSFs are the same to ± 5% and the host galaxy magnitudes are the same to ±0.1 mag.

Original languageEnglish (US)
Pages (from-to)557-564
Number of pages8
JournalAstrophysical Journal
Issue number2 PART I
StatePublished - 1996

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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