This paper presents NICMOS images of the nucleus and emission line regions in
NGC 1068. The location of the nucleus relative to the emission line features is
established and the physics underlying ...the morphology is discussed.
We use the ultraviolet and optical WFPC2 and near-infrared NICMOS images of
the Hubble Deep Field North to measure and statistically compare an array of
parameters for over 250 of the galaxies it ...contains. These parameters include
redshift, rest-frame visible asymmetry and concentration, bolometric luminosity
and extinction-corrected star formation rate. We find only one strong
correlation, between bolometric luminosity and star formation rate, from which
early-type galaxies noticeably deviate. When our asymmetry measurements are
combined with those of a sample of nearby galaxies covering the full Hubble
sequence, we find a weak correlation between redshift and rest-frame visible
asymmetry, consistent with the qualitative evidence of galaxy morphological
evolution from these and other deep Hubble Space Telescope images. The mean
values of these asymmetry measurements show a monotonic increase with redshift
interval over the range 0 < z < 2, increasing by a factor of approximately
three. If this trend is real, it suggests that galaxy morphological evolution
is a gradual process that is continuing through the present cosmological epoch.
There is evidence that the dominant source of this evolution is the "minor"
mergers of disk galaxies with smaller companions, which could also transform
late-type spiral galaxies into early-type spiral galaxies. Interestingly, in
contrast to local galaxies we find no correlations between star formation rate
and either UV or visible asymmetry. This could arise if the star formation of
high-redshift galaxies proceeds in episodes that are short (~ 100 Myr) relative
to the time scales over which galaxy mergers produce strong asymmetries (~ 500
Myr), a result suggested by the high star formation rates of Lyman break
galaxies.
We present a photometric analysis of all high Galactic lattitude (|b| > 20d)
broad-band parallel images taken by the Near Infrared Camera and Multi-Object
Spectrometer (NICMOS) instrument during its ...initial lifetime in HST Cycle 7.
These images, taken through the F110W and F160W filters, reach a mean 3-sigma
limiting magnitude of approximately 22 in both bands, and cover a total area of
approximately 92 square arcminutes. The reddest of the 358 galaxies detected
have F110W-F160W colors and F160W magnitudes consistent with being a
combination of both dusty star-forming and evolved early-type galaxies at 1 < z
< 2. The surface density of these galaxies is comparable to that of the
population of Extremely Red Objects (EROs) discovered in ground-based surveys
(~ 100 deg-2), suggesting that EROs also represent a combination of both galaxy
types in this redshift range. Roughly 10% of the detected galaxies appear to be
blue compact dwarf galaxies at z < 1, a result consistent with studies of the
HST Medium Deep Survey Fields. The surface density of these objects down to
magnitude of 22 in F160W is ~ 300 deg-2. None of the 681 point sources detected
have F110W-F160W colors matching those expected for QSOs whose continua have
been significantly reddened by internal dust. Our data limit the surface
density of such QSOs to be < 50 deg-2 down the mean limiting magnitudes of the
sample images. Since the surface density of QSOs detected on the basis of
ultraviolet excess in optical surveys to comparable depth is ~ 100 deg-2, this
argues against the suggestion that dust-reddened QSOs comprise the undetected
majority of the QSO population. The F110W-F160W color can also be used to
identify unreddened QSOs at z > 8, but we find no such candidates. This is
consistent with the evidence that QSO space density declines sharply at z > 5.
Astron.J. 119 (2000) 1062 We present positions, magnitudes, sizes and morphological classifications for
111 galaxies discovered in the Hubble Space Telescope NICMOS Camera 1 and
Camera 2 parallel ...fields. We combine the magnitudes measured in the JHK-analog
filters with those from deep ground-based images in V and/or R to measure
photometric redshifts for 71 objects using Bruzual-Charlot population synthesis
models. We find that these objects fall in the range z ~ 0.0 - 2.7, with a mean
redshift of 0.8 and a mean luminosity of 1.6 L*. The NICMOS images reveal many
of the objects to be ordered spirals and ellipticals similar to those in the
local universe. However, we find a higher fraction (~ 14%) of morphologically
peculiar and/or interacting galaxies than is observed among local galaxies (~
3% - 4%). This is consistent with the results from other deep HST images
including the Hubble Deep Field and Hubble Medium Deep Survey Field that the
fraction of peculiar and interacting galaxies increases with redshift. As the
NICMOS images of the sample galaxies cover their rest-frame near infrared and
optical emission, this result increases confidence that such changes in
morphology are genuine, as opposed to an effect produced by viewing galaxies in
the rest-frame ultraviolet. We also find that at least 26 of the sample
galaxies appear to be members of (non-interacting) pairs or groups, based on
their proximity to one another and photometric redshifts. This is consistent
with the results of recent ground-based optical surveys covering larger areas,
and with the detection of galaxy groups and filaments at redshifts higher than
those covered by our sample.
This paper presents NICMOS images of the nucleus and emission line regions in NGC 1068. The location of the nucleus relative to the emission line features is established and the physics underlying ...the morphology is discussed.
We use the ultraviolet and optical WFPC2 and near-infrared NICMOS images of the Hubble Deep Field North to measure and statistically compare an array of parameters for over 250 of the galaxies it ...contains. These parameters include redshift, rest-frame visible asymmetry and concentration, bolometric luminosity and extinction-corrected star formation rate. We find only one strong correlation, between bolometric luminosity and star formation rate, from which early-type galaxies noticeably deviate. When our asymmetry measurements are combined with those of a sample of nearby galaxies covering the full Hubble sequence, we find a weak correlation between redshift and rest-frame visible asymmetry, consistent with the qualitative evidence of galaxy morphological evolution from these and other deep Hubble Space Telescope images. The mean values of these asymmetry measurements show a monotonic increase with redshift interval over the range 0 < z < 2, increasing by a factor of approximately three. If this trend is real, it suggests that galaxy morphological evolution is a gradual process that is continuing through the present cosmological epoch. There is evidence that the dominant source of this evolution is the "minor" mergers of disk galaxies with smaller companions, which could also transform late-type spiral galaxies into early-type spiral galaxies. Interestingly, in contrast to local galaxies we find no correlations between star formation rate and either UV or visible asymmetry. This could arise if the star formation of high-redshift galaxies proceeds in episodes that are short (~ 100 Myr) relative to the time scales over which galaxy mergers produce strong asymmetries (~ 500 Myr), a result suggested by the high star formation rates of Lyman break galaxies.
We present a photometric analysis of all high Galactic lattitude (|b| > 20d) broad-band parallel images taken by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) instrument during its ...initial lifetime in HST Cycle 7. These images, taken through the F110W and F160W filters, reach a mean 3-sigma limiting magnitude of approximately 22 in both bands, and cover a total area of approximately 92 square arcminutes. The reddest of the 358 galaxies detected have F110W-F160W colors and F160W magnitudes consistent with being a combination of both dusty star-forming and evolved early-type galaxies at 1 < z < 2. The surface density of these galaxies is comparable to that of the population of Extremely Red Objects (EROs) discovered in ground-based surveys (~ 100 deg-2), suggesting that EROs also represent a combination of both galaxy types in this redshift range. Roughly 10% of the detected galaxies appear to be blue compact dwarf galaxies at z < 1, a result consistent with studies of the HST Medium Deep Survey Fields. The surface density of these objects down to magnitude of 22 in F160W is ~ 300 deg-2. None of the 681 point sources detected have F110W-F160W colors matching those expected for QSOs whose continua have been significantly reddened by internal dust. Our data limit the surface density of such QSOs to be < 50 deg-2 down the mean limiting magnitudes of the sample images. Since the surface density of QSOs detected on the basis of ultraviolet excess in optical surveys to comparable depth is ~ 100 deg-2, this argues against the suggestion that dust-reddened QSOs comprise the undetected majority of the QSO population. The F110W-F160W color can also be used to identify unreddened QSOs at z > 8, but we find no such candidates. This is consistent with the evidence that QSO space density declines sharply at z > 5.
We present positions, magnitudes, sizes and morphological classifications for 111 galaxies discovered in the Hubble Space Telescope NICMOS Camera 1 and Camera 2 parallel fields. We combine the ...magnitudes measured in the JHK-analog filters with those from deep ground-based images in V and/or R to measure photometric redshifts for 71 objects using Bruzual-Charlot population synthesis models. We find that these objects fall in the range z ~ 0.0 - 2.7, with a mean redshift of 0.8 and a mean luminosity of 1.6 L*. The NICMOS images reveal many of the objects to be ordered spirals and ellipticals similar to those in the local universe. However, we find a higher fraction (~ 14%) of morphologically peculiar and/or interacting galaxies than is observed among local galaxies (~ 3% - 4%). This is consistent with the results from other deep HST images including the Hubble Deep Field and Hubble Medium Deep Survey Field that the fraction of peculiar and interacting galaxies increases with redshift. As the NICMOS images of the sample galaxies cover their rest-frame near infrared and optical emission, this result increases confidence that such changes in morphology are genuine, as opposed to an effect produced by viewing galaxies in the rest-frame ultraviolet. We also find that at least 26 of the sample galaxies appear to be members of (non-interacting) pairs or groups, based on their proximity to one another and photometric redshifts. This is consistent with the results of recent ground-based optical surveys covering larger areas, and with the detection of galaxy groups and filaments at redshifts higher than those covered by our sample.
