The Theta-z Relationship for HST bulges and disks out to z$\leq$0.6
Previous
abstract
Next
abstract
- Session 57 -- Galaxies III
- Oral presentation, Thursday, January 13, 10:15-11:45, Salon IV Room (Crystal Gateway)
[57.05] The Theta-z Relationship for HST bulges and disks out to z$\leq$0.6
S. Mutz, R. Windhorst, P. C. Schmidtke, B. Franklin, S. M. Pascarelle (Arizona State University), R. E. Griffiths, K. U. Ratnatunga, L. W. Neuschaefer (Johns Hopkins University), R. S. Ellis, G. Gilmore (IoA, Cambridge), R. F. Green (NOAO), J. P. Huchra (CfA), G. D. Illingworth, D. C. Koo (UCSC), A. Tyson (Bell Labs)
We present a systematic project as part of the HST Medium-Deep Survey (``MDS'')
to determine scale-lengths for about 72 galaxies down to V$\le$22.5 (I$\le$21)
mag with the Wide Field/Planetary Camera (at deconvolved FWHM$\le$0.2''). We
measured redshifts with the MMT and the 100 inch duPont out to z=0.6. The HST
galaxies have scale-lengths in the range 0.3$
We compare the sample of HST galaxy bulges with $r^{1/4}$ profiles to the Seven
Samurai sample of nearby ellipticals (Burstein et al. 1987). For $H_{o}$=75
km/s/Mpc, the latter follow the $\Theta$-z relation out to z=0.03 for a best fit
$r_{e}$=5.7 kpc. In the redshift range 0.2$< z<$0.6 our HST/MDS sample shows a
lack of bulges with scale-lengths larger than the $r_{e}$=5.7 kpc models for
$q_{o}$=0.01---1.0. We discuss various possible selection effects, such as the
selection against faint low surface brightness galaxies in both HST images and
MMT spectra at the faintest magnitudes. Our result may nontheless indicate that
elliptical galaxy scale-lengths have evolved with cosmic time, in that they were
smaller in the past, due to e.g. an epoch dependent merger rate or dynamical
evolution. We similarly analyzed our HST/MDS sample of galaxy disk
scale-lengths out to z=0.6, and compared this to the RC3 catalog of nearby
spirals. The latter has more complicated selection effects due to its limits in
both diameter and $B_{T}$-mag. Taking as best value for the local disk
scale-length $r_{e}$=3.4 kpc (for $H_{o}$=75km/s/Mpc), we find a more
symmetrical distribution of disk scale-lengths around the models out to z=0.6.
This implies that galaxy disks may have been stable since z$\sim$1.0.
This work was supported by NASA/HST grants GO-2684-0*-87A from STScI, which is
operated by AURA, Inc., under NASA contract NAS5-26555.
Thursday
program listing