• DOI:10.1086/308616
• Corpus ID: 17721022

The Hubble Space Telescope Survey of BL Lacertae Objects. II. Host Galaxies

@article{Urry1999TheHS,
  title={The Hubble Space Telescope Survey of BL Lacertae Objects. II. Host Galaxies},
  author={C. Megan Urry and Riccardo Scarpa and Matthew J. O'Dowd and Renato Falomo and Joseph E. Pesce and Aldo Treves},
  journal={The Astrophysical Journal},
  year={1999},
  volume={532},
  pages={816-829}
}

• C. Urry, R. Scarpa, +3 authors A. Treves
• Published 7 November 1999
• Physics
• The Astrophysical Journal

We have used the Hubble Space Telescope (HST ) WFPC2 camera to survey 132 BL Lac objects com- prising seven complete radio-, X-ray¨, and optically selected samples. We obtained useful images for 110 targets spanning the redshift range These represent an unbiased subsample of the original 0 ( z ( 1.3. 132 since they were snapshots selected to —ll random holes in the HST schedule. The exposure times ranged from a few hundred to D1000 s, increasing with redshift. Most images were taken in the F702W —lter; those already observed in F814W during Cycle 5 were reobserved in F606W to give broader wave- length coverage. The data were analyzed uniformly, and both statistical and systematic errors were esti- mated (the latter dominate). In of the BL Lac images, host galaxies are detected, including nearly all 2 for z \ 0.5 (58 of 63). In contrast, only one-quarter of the BL Lac objects with z ( 0.5 (six of 22) were resolved because of the relatively short exposure times, and these tend to be very luminous host galaxies. The highest redshift host galaxy detected is in a BL Lac object at z \ 0.664. HST data add critical mor- phological information in the range a few tenths to a few arcseconds. In 58 of the 72 resolved host galaxies, a de Vaucouleurs pro—le is signi—cantly preferred, at con—dence, over a pure exponential Z99% disk; the two —ts are comparable in the remaining 14 cases because of their generally lower signal-to- noise ratios. These results limit the number of disk systems to at most 8% of BL Lac objects (at 99% con—dence) and are consistent with all BL Lac host galaxies being ellipticals. The detected host galaxies are luminous ellipticals with a median absolute K-corrected magnitude of mag (rms M R D (23.7 ^ 0.6 dispersion), at least 1 mag brighter than M* and comparable to brightest cluster galaxies. The galaxy morphologies are generally smooth and undisturbed, with small or negligible ellipticities