19 research outputs found
Predicting dust extinction from the stellar mass of a galaxy
We investigate how the typical dust extinction of H-alpha luminosity from a
star-forming galaxy depends upon star formation rate (SFR), metallicity and
stellar mass independently, using a sample of ~90,000 galaxies from Data
Release 7 of the Sloan Digital Sky Survey (SDSS). We measure extinctions
directly from the Balmer decrement of each source, and while higher values of
extinction are associated with an increase in any of the three parameters, we
demonstrate that the fundamental property that governs extinction is stellar
mass. After this mass-dependent relationship is removed, there is very little
systematic dependence of the residual extinctions with either SFR or
metallicity, and no significant improvement is obtained from a more general
parameterisation. In contrast to this, if either a SFR-dependent or
metallicity-dependent extinction relationship is applied, the residual
extinctions show significant trends that correlate with the other parameters.
Using the SDSS data, we present a relationship to predict the median dust
extinction of a sample of galaxies from its stellar mass, which has a scatter
of ~0.3 mag. The relationship was calibrated for H-alpha emission, but can be
more generally applied to radiation emitted at other wavelengths. These results
have important applications for studies of high-redshift galaxies, where
individual extinction measurements are hard to obtain but stellar mass
estimates can be relatively easily estimated from long-wavelength data.Comment: Accepted for publication in MNRAS. 12 pages. Dedicated to the memory
of Timothy Gar
Radio source stacking and the infrared / radio correlation at microJy flux densities
We investigate the infrared / radio correlation using the technique of source
stacking, in order to probe the average properties of radio sources that are
too faint to be detected individually. We compare the two methods used in the
literature to stack sources, and demonstrate that the creation of stacked
images leads to a loss of information. We stack infrared sources in the Spitzer
extragalactic First Look Survey (xFLS) field, and the three northern Spitzer
Wide-area Infrared Extragalactic survey (SWIRE) fields, using radio surveys
created at 610 MHz and 1.4 GHz, and find a variation in the absolute strength
of the correlation between the xFLS and SWIRE regions, but no evidence for
significant evolution in the correlation over the 24-um flux density range 150
uJy - 2 mJy. We carry out the first radio source stacking experiment using
70-um-selected galaxies, and find no evidence for significant evolution over
the 70-um flux density range 10 mJy - 100 mJy.Comment: 11 pages, 12 figures. Accepted for publication in MNRA
Comparative Analysis Between Physical Activity Affect and Discrete Emotions in College Students
Objective: The purpose of this study was to investigate empirical distinctness and overlap between physical activity (PA) affect and emotions as well as potential unique relationships with PA beliefs and behaviors. Specifically, researchers wanted to explore the level of shared variance amongst discrete emotions and affect, which in effect tested the jingle-jangle fallacy that can be present in psychometric evaluation of related constructs.
Participants: College students (N=519; Mage= 20.47) enrolled in PA courses at two universities in the Southeastern United States completed questionnaires concerning their PA related emotions, affect, self-efficacy, and self-reported PA.
Methods: Confirmatory factor analysis and structural modeling were used to evaluate factor structure and hypothesized relationships.
Results: Sound factor analysis was identified with affect related to several emotions, including strong correlations between enjoyment and positive affect, suggesting some construct and measurement intersection. Regression results showed emotions produced stronger relationships with self-efficacy and PA compared to affect.
Conclusions: While conceptual overlap did exist, measuring several discrete emotions over the dichotomous affective measure may be more insightful and provide specificity in explaining PA decisions. More research is needed on the use of PA emotions
HiZELS: the High Redshift Emission Line Survey with UKIRT
In these proceedings we report on HiZELS, the High-z Emission Line Survey,
our successful panoramic narrow-band Campaign Survey using WFCAM on UKIRT to
detect and study emission line galaxies at z~1-9. HiZELS employs the H2(S1)
narrow-band filter together with custom-made narrow-band filters in the J and
H-bands, with the primary aim of delivering large, identically-selected samples
of H-alpha emitting galaxies at redshifts of 0.84, 1.47 and 2.23. Comparisons
between the luminosity function, the host galaxy properties, the clustering,
and the variation with environment of these H-alpha-selected samples are
yielding unique constraints on the nature and evolution of star-forming
galaxies, across the peak epoch of star-formation activity in the Universe. We
provide a summary of the project status, and detail the main scientific results
obtained so far: the measurement of the evolution of the cosmic star-formation
rate density out to z > 2 using a single star-formation indicator,
determination of the morphologies, environments and dust-content of the
star-forming galaxies, and a detailed investigation of the evolution of their
clustering properties. We also summarise the on-going work and future goals of
the project.Comment: To appear in proceedings of "UKIRT at 30: A British Success Story"
A 610-MHz survey of the ELAIS-N1 field with the Giant Metrewave Radio Telescope - Observations, data analysis and source catalogue
Observations of the ELAIS-N1 field taken at 610 MHz with the Giant Metrewave
Radio Telescope are presented. Nineteen pointings were observed, covering a
total area of 9 square degrees with a resolution of 6" x 5", PA +45 deg. Four
of the pointings were deep observations with an rms of 40 microJy before
primary beam correction, with the remaining fifteen pointings having an rms of
70 microJy. The techniques used for data reduction and production of a
mosaicked image of the region are described, and the final mosaic is presented,
along with a catalogue of 2500 sources detected above 6 sigma. This work
complements the large amount of optical and infrared data already available on
the region. We calculate 610-MHz source counts down to 270 microJy, and find
further evidence for the turnover in differential number counts below 1 mJy,
previously seen at both 610 MHz and 1.4 GHz.Comment: 12 pages, 18 figures, two tables. Table 1 can be found in full via
http://www.mrao.cam.ac.uk/surveys/ . Accepted for publication in MNRA
DOES "CENTRAL" OBESITY PREDICT CORONARY ARTERY DISEASE?
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26676/1/0000220.pd
PROPORTION OF NEWLY OBESE AND CHRONIC OBESE AT DIFFERENT AGES
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27877/1/0000291.pd
A population of high-redshift type-2 quasars-II. Radio Properties
We present multi-frequency radio observations of a sample of z~2 obscured
(type-2) quasars in the Spitzer extragalactic First Look Survey area. We
combine the public data at 1.4 GHz, used in the selection of these sources,
with new observations at 610 MHz (GMRT) and at 4.9 GHz (VLA). We find the
sample includes sources with steep, flat and gigahertz-peaked spectra. There
are no strong correlations between the presence or absence of emission lines in
the optical spectra and the radio spectral properties of the sample. However,
there are no secure flat-spectrum type-2 quasars with narrow emission lines
which would be problematic for unified schemes. Most of the population have
straight radio spectra with spectral index alpha~1 as is expected for
developed, potentially FRI-like, jets in which continous injection of
relativistic electrons is accompanied by inverse-Compton losses against the
cosmic microwave background.Comment: 6 pages, 2 colour figures, submitted to MNRA
WHICH TRANSFORMATION FOR NORMALISING SKINFOLD AND FATNESS DISTRIBUTIONS?
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26472/1/0000007.pd