150 research outputs found
The social behaviours of visually impaired preschool children.
Dept. of Psychology. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1989 .C763. Source: Masters Abstracts International, Volume: 40-07, page: . Thesis (M.A.)--University of Windsor (Canada), 1989
Disk Growth in Bulge-Dominated Galaxies: Molecular Gas and Morphological Evolution
Substantial numbers of morphologically regular early-type (elliptical and
lenticular) galaxies contain molecular gas, and the quantities of gas are
probably sufficient to explain recent estimates of the current level of star
formation activity. This gas can also be used as a tracer of the processes that
drive the evolution of early-type galaxies. For example, in most cases the gas
is forming dynamically cold stellar disks with sizes in the range of hundreds
of pc to more than one kpc, although there is typically only 1% of the total
stellar mass currently available to form young stars. The numbers are still
small, but the molecular kinematics indicate that some of the gas probably
originated from internal stellar mass loss while some was acquired from
outside. Future studies will help to quantify the role of molecular gas
(dissipational processes) in the formation of early-type galaxies and their
evolution along the red sequence.Comment: 4 pages. To appear in the proceedings of IAU Symposium 245,
"Formation and Evolution of Galaxy Bulges," M. Bureau, E. Athanassoula, and
B. Barbuy, ed
ISM chemistry in metal rich environments: molecular tracers of metallicity
In this paper we use observations of molecular tracers in metal rich and
alpha-enhanced galaxies to study the effect of abundance changes on molecular
chemistry. We selected a sample of metal rich spiral and star bursting objects
from the literature, and present here new data for a sample of early-type
galaxies (ETGs). We conducted the first survey of CS and methanol emission in
ETGs, detecting 7 objects in CS, and 5 in methanol emission. We find evidence
to support the hypothesis that CS is a better tracer of dense star-forming gas
than HCN. We suggest that the methanol emission in these sources is driven by
dust mantle destruction due to ionisation from high mass star formation, but
cannot rule out shocks dominating in some sources. The derived source averaged
CS/methanol column densities and rotation temperatures are similar to those
found in normal spiral and starburst galaxies, suggesting dense clouds are
little affected by the differences between galaxy types. Finally we used the
total column density ratios for our galaxy samples to show for the first time
that some molecular tracers do seem to show systematic variations that appear
to correlate with metallicity, and that these variations roughly match those
predicted by chemical models. Using this fact, the chemical models of Bayet et
al. (2012b), and assumptions about the optical depth we are able to roughly
predict the metallicity of our spiral and ETG sample, with a scatter of ~0.3
dex. We provide the community with linear approximations to the relationship
between the HCN and CS column density ratio and metallicity. Further study will
clearly be required to determine if this, or any, molecular tracer can be used
to robustly determine gas-phase metallically, but that a relationship exists at
all suggests that in the future it may be possible to calibrate a metallicity
indicator for the molecular interstellar medium (abridged).Comment: 14 pages, 9 figures. MNRAS, accepte
Inter-informant agreement and childhood depression.
In the present study, the influence of several variables on parent-child agreement for child, mother, and father reports of child functioning were investigated. Variables included the specificity of the depression measure used, child self-reports of global self-worth, and parent reported pathology. Harter\u27s (Harter, Marold, & Whitesell, 1991) model of the mediational role of self-worth as a risk factor of depression and suicidal ideation was also examined. This model was originally developed for use with adolescents but was tested with elementary school age children in this study. Ninety-two elementary school children (9 to 12 years of age), their mothers, and a subgroup of their fathers completed parent and child versions of the Self-Perception Profile for Children (SPPC: Harter, 1985a), the Social Support Scale for Children and Adolescents (SSSC: Harter, 1985b), the Dimensions of Depression Profile for Children and Adolescents (DDPC: Harter & Nowakowski, 1987), and the Children\u27s Depression Inventory (CDI: Kovacs, 1992). Parents also provided self-reports of depression by completing the Beck Depression Inventory (BDI: Beck & Steer, 1987). Compared to previous research (e.g., see Achenbach, McConaughy, & Howell, 1987), agreement was not improved for children and mothers, children and fathers, or mothers and fathers. For example, the domain specific nature of the DDPC did not result in an improvement in agreement between informants over the more global CDI. In addition, children with low global self-worth and their parents were not observed to report greater parent-child agreement compared to children and their parents with high global self-worth on the SPPC, SSSC, DDPC, and CDI. While parent self-reports of depression on the BDI were positively related to parent reports of child functioning on two measures of depression, they were not related to child self-reports. Last, child and mother reports provided partial support for Harter\u27s model of self-worth and risk factors associated with depression and suicidal ideation. These results support the use of child self-reports in the assessment process and in school-based screening programs for the early identification of children at risk for depression or other school related difficulties.Dept. of Psychology. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1994 .C76. Source: Dissertation Abstracts International, Volume: 56-01, Section: A, page: 0141. Adviser: Julie Hakim-Larson. Thesis (Ph.D.)--University of Windsor (Canada), 1994
Evidence of boosted 13CO/12CO ratio in early-type galaxies in dense environments
We present observations of CO(1-0) in 17 Combined Array for Research
in Millimeter Astronomy (CARMA) Atlas3D early-type galaxies (ETGs), obtained
simultaneously with CO(1-0) observations. The CO in six ETGs is
sufficiently bright to create images. In these 6 sources, we do not detect any
significant radial gradient in the CO/CO ratio between the
nucleus and the outlying molecular gas. Using the CO channel maps as 3D
masks to stack the CO emission, we are able to detect 15/17 galaxies to
(and 12/17 to at least 5) significance in a spatially
integrated manner. Overall, ETGs show a wide distribution of
CO/CO ratios, but Virgo cluster and group galaxies preferentially
show a CO/CO ratio about 2 times larger than field galaxies,
although this could also be due to a mass dependence, or the CO spatial extent
(). ETGs whose gas has a morphologically-settled
appearance also show boosted CO/CO ratios. We hypothesize that
this variation could be caused by (i) the extra enrichment of gas from
molecular reprocessing occurring in low-mass stars (boosting the abundance of
C to C in the absence of external gas accretion), (ii) much
higher pressure being exerted on the midplane gas (by the intracluster medium)
in the cluster environment than in isolated galaxies, or (iii) all but the
densest molecular gas clumps being stripped as the galaxies fall into the
cluster. Further observations of CO in dense environments, particularly
of spirals, as well as studies of other isotopologues, should be able to
distinguish between these hypotheses.Comment: 13 pages, 3 tables, 7 figures, accepted by MNRA
Cold Molecular Gas in Merger Remnants. I. Formation of Molecular Gas Disks
We present the 1 kpc resolution 12CO imaging study of 37 optically selected local merger remnants using new and archival interferometric maps obtained with ALMA, CARMA, the Submillimeter Array, and the Plateau de Bure Interferometer. We supplement a sub-sample with single-dish measurements obtained at the Nobeyama Radio Observatory 45 m telescope for estimating the molecular gas mass (107 – 11 M ☉) and evaluating the missing flux of the interferometric measurements. Among the sources with robust CO detections, we find that 80% (24/30) of the sample show kinematical signatures of rotating molecular gas disks (including nuclear rings) in their velocity fields, and the sizes of these disks vary significantly from 1.1 kpc to 9.3 kpc. The size of the molecular gas disks in 54% of the sources is more compact than the K-band effective radius. These small gas disks may have formed from a past gas inflow that was triggered by a dynamical instability during a potential merging event. On the other hand, the rest (46%) of the sources have gas disks that are extended relative to the stellar component, possibly forming a late-type galaxy with a central stellar bulge. Our new compilation of observational data suggests that nuclear and extended molecular gas disks are common in the final stages of mergers. This finding is consistent with recent major-merger simulations of gas-rich progenitor disks. Finally, we suggest that some of the rotation-supported turbulent disks observed at high redshifts may result from galaxies that have experienced a recent major merger
Down but not out: properties of the molecular gas in the stripped Virgo Cluster early-type galaxy NGC4526
We present ALMA data on the 3mm continuum emission, CO isotopologues (12CO,
13CO, C18O), and high-density molecular tracers (HCN, HCO+, HNC, HNCO, CS, CN,
and CH3OH) in NGC4526. These data enable a detailed study of the physical
properties of the molecular gas in a longtime resident of the Virgo Cluster;
comparisons to more commonly-studied spiral galaxies offer intriguing hints
into the processing of molecular gas in the cluster environment. Many molecular
line ratios in NGC4526, along with our inferred abundances and CO/H2 conversion
factors, are similar to those found in nearby spirals. One striking exception
is the very low observed 12CO/13CO(1-0) line ratio, , which is
unusually low for spirals though not for Virgo Cluster early-type galaxies. We
carry out radiative transfer modeling of the CO isotopologues with some
archival (2-1) data, and we use Bayesian analysis with Markov chain Monte Carlo
techniques to infer the physical properties of the CO-emitting gas. We find
surprisingly low [12CO/13CO] abundance ratios of and
at radii of 0.4 kpc and 1 kpc. The emission from the
high-density tracers HCN, HCO+, HNC, CS and CN is also relatively bright, and
CN is unusually optically thick in the inner parts of NGC4526. These features
hint that processing in the cluster environment may have removed much of the
galaxy's relatively diffuse, optically thinner molecular gas along with its
atomic gas. Angular momentum transfer to the surrounding intracluster medium
may also have caused contraction of the disk, magnifying radial gradients such
as we find in [13CO/C18O]. More detailed chemical evolution modeling would be
interesting in order to explore whether the unusual [12CO/13CO] abundance ratio
is entirely an environmental effect or whether it also reflects the relatively
old stellar population in this early-type galaxy.Comment: Submitted to ApJ. Comments are welcome
Quantifying non-star formation associated 8um dust emission in NGC 628
Combining Ha and IRAC images of the nearby spiral galaxy NGC 628, we find
that between 30-43% of its 8um dust emission is not related to recent star
formation. Contributions from dust heated by young stars are separated by
identifying HII regions in the Ha map and using these areas as a mask to
determine the 8um dust emission that must be due to heating by older stars.
Corrections are made for sub-detection-threshold HII regions, photons escaping
from HII regions and for young stars not directly associated to HII regions
(i.e. 10-100 Myr old stars). A simple model confirms this amount of 8um
emission can be expected given dust and PAH absorption cross-sections, a
realistic star-formation history, and the observed optical extinction values. A
Fourier power spectrum analysis indicates that the 8um dust emission is more
diffuse than the Ha emission (and similar to observed HI), supporting our
analysis that much of the 8um-emitting dust is heated by older stars. The 8um
dust-to-Ha emission ratio declines with galactocentric radius both within and
outside of HII regions, probably due to a radial increase in disk transparency.
In the course of this work, we have also found that intrinsic diffuse Ha
fractions may be lower than previously thought in galaxies, if the differential
extinction between HII regions and diffuse regions is taken into account.Comment: 14 pages, 11 figures, accepted in Ap
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