102 research outputs found
Hubble Space Telescope Imaging of Star-Forming Galaxies at Redshifts z>3
We present HST images of star-forming galaxies at redshifts z>3. These
galaxies have been color selected for having a Lyman discontinuity in the
otherwise flat (in f_\nu units) UV spectra of unreddened star formation. The
spectroscopic confirmation of these z>3 galaxies is reported in a companion
paper (Steidel et al. 1996). The HST images probe the rest-frame UV at
1400--1900 Ang and show that the morphologies of the z>3 galaxies are generally
compact, although we find a few cases of more diffuse light profiles and
objects comprised of multiple compact structures. Overall, the dispersion of
morphologies is relatively narrow, in contrast to the variety found in
star-forming galaxies at intermediate redshifts (z~1). The galaxies with
compact morphology are typically characterized by a small but resolved
``core'', approximately <0.7 arcsec in radius, or about 5 h_50 (8.5 h_50) kpc
with q_0=0.5 (0.05), and half-light radii of 0.2--0.3 arcsec, or 1.4--2.1 h_50
(2.4--3.6 h_50) kpc. These sizes and scale lengths are similar to those of
present-day bulges or intermediate-luminosity spheroids. The ``cores'' are
often surrounded by lower surface-brightness nebulosities, generally
asymmetrically distributed. The minority of more diffuse galaxies do not
possess this core, and an exponential function provides a very good fit to
their light profiles. In contrast to highly elongated or irregular structures,
such as ``chain galaxies'', that are found at , the z>3 galaxies are
characterized by a relatively high degree of spherical symmetry. Morphology,
space density, star-formation rates, masses, and epoch of the star-formation
phase all support the hypothesis that we have identified the progenitors of
present-day luminous galaxies at the epoch when they were forming the stars ofComment: 15 pages; The Astrophysical Journa
Filaments and Ionized Gas in the Vicinity of 3C 244.1
We present results of Hubble Space Telescope observations of the radio galaxy
3C 244.1. The broadband F702W (R) and F555W (V) images (WFPC2/PC) show an
elliptical galaxy and gaseous filaments and blobs surrounding it. In the
narrow-band ramp filter, dominated by [OIII]lambda5007, these filaments are
bright and have the same morphology as the broad band images. To the south, the
filaments have a cone-shaped structure and the radio jet is located at the
center of this cone. To the north of the galaxy, the structure is found near
the nucleus of the galaxy within its elliptical profile. From the photometry,
the two brighter structures seem to be extended narrow line emission regions
(ENLRs). The comparison with diagnostic line ratios shows that the observed
emission is consistent with interactions between the expanding radio-jet and
the local denser medium.Comment: 10 pages and 3 figures, accepted for publication in Ap
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