153 research outputs found
An Infrared Comparison of Type-1 and Type-2 Quasars
We model the optical to far-infrared SEDs of a sample of six type-1 and six
type-2 quasars selected in the mid-infrared. The objects in our sample are
matched in mid-IR luminosity and selected based on their Spitzer IRAC colors.
We obtained new targeted Spitzer IRS and MIPS observations and used archival
photometry to examine the optical to far-IR SEDs. We investigate whether the
observed differences between samples are consistent with orientation-based
unification schemes. The type-1 objects show significant emission at 3 micron.
They do not show strong PAH emission and have less far-IR emission on average
when compared to the type-2 objects. The SEDs of the type-2 objects show a wide
assortment of silicate features, ranging from weak emission to deep silicate
absorption. Some also show strong PAH features. In comparison, silicate is only
seen in emission in the type-1 objects. This is consistent with some of the
type-2s being reddened by a foreground screen of cooler dust, perhaps in the
host galaxy itself. We investigate the AGN contribution to the far-IR emission
and find it to be significant. We also estimate the star formation rate for
each of the objects by integrating the modeled far-IR flux and compare this
with the SFR found from PAH emission. We find the type-2 quasars have a higher
average SFR than the type-1 quasars based on both methods, though this could be
due to differences in bolometric luminosities of the objects. While we find
pronounced differences between the two types of objects, none of them are
inconsistent with orientation-based unification schemes.Comment: Accepted for publication in Ap
The Spitzer mid-infrared AGN survey. II-the demographics and cosmic evolution of the AGN population
We present luminosity functions derived from a spectroscopic survey of AGN
selected from Spitzer Space Telescope imaging surveys. Selection in the
mid-infrared is significantly less affected by dust obscuration. We can thus
compare the luminosity functions of the obscured and unobscured AGN in a more
reliable fashion than by using optical or X-ray data alone. We find that the
AGN luminosity function can be well described by a broken power-law model in
which the break luminosity decreases with redshift. At high redshifts
(), we find significantly more AGN at a given bolometric luminosity than
found by either optical quasar surveys or hard X-ray surveys. The fraction of
obscured AGN decreases rapidly with increasing AGN luminosity, but, at least at
high redshifts, appears to remain at \% even at bolometric
luminosities . The data support a picture in which the
obscured and unobscured populations evolve differently, with some evidence that
high luminosity obscured quasars peak in space density at a higher redshift
than their unobscured counterparts. The amount of accretion energy in the
Universe estimated from this work suggests that AGN contribute about 12\% to
the total radiation intensity of the Universe, and a high radiative accretion
efficiency is required to match current
estimates of the local mass density in black holes.Comment: 14 pages, accepted by Ap
Are Advanced Practice Registered Nurses In Mississippi Participating In Practices That Advocate The Nursing Profession
Previous research studies have focused on patient outcomes related to healthcare interventions, but there is little research available regarding nurses’ involvement in activities that would advance the profession. Advanced Practice Registered Nurses’ (APRN) contributions to the healthcare system lead to direct improvement of patient outcomes through research, mentoring new professionals, and participating in professional organizations. The theoretical motivation behind the study is Ray’s Theory of Bureaucratic Caring that proposed healthcare personnel consider incorporation of the business aspects of healthcare to propel nursing into the future. Ray dared nurses to become leaders in the field, understand the corporate aspects of health care, evolve bedside nursing through research activity, and build future nurse leaders with political and mentorship works. The study considers characteristics Ray demanded nurses take to control the future of the profession and advance the nurse’s role in healthcare. The study will assess current level of involvement of APRNs in three activities that directly advance the profession. Survey questions will address demographic information and the degree of participation in the three specific activities. The study will use a quantitative approach through randomized surveys distributed through face-to-face encounters, Survey Monkey, social media, and email. Inclusion criteria is limited to practicing APRNs within any specialty with a master’s level education or higher
Teacher education in practice: Reconciling contexts, practices, and theories
This is the author's accepted manuscript. The original publication is available at http://dx.doi.org/10.1080/08856257.2013.778114.This paper reports findings from an 18-month qualitative study that followed the experiences of nine teacher residents, their site professors, site coordinators, clinical teachers and principals in three professional learning schools. The study examined the tensions that emerged as teacher preparation theory intersected with the context-bound realities of daily life in schools and the political constraints that diminish possibilities for inclusive education. The paper addresses implications for teacher preparation programmes by reporting how teacher residents negotiated their understanding of and commitment for inclusive education through three themes: (a) critical reflection as an emergent practice, (b) whose learning, and (c) the trouble with behaviour. Interpreting these themes has implications for programmatic designs in teacher preparation
Shocked POststarbust Galaxy Survey I: Candidate Poststarbust Galaxies with Emission Line Ratios Consistent with Shocks
[Abridged] The Shocked POststarburst Galaxy Survey (SPOGS) aims to identify
transforming galaxies, in which the nebular lines are excited via shocks
instead of through star formation processes. Utilizing the OSSY measurements on
the Sloan Digital Sky Survey Data Release 7 catalog, we applied Balmer
absorption and shock boundary criteria to identify 1,067 SPOG candidates
(SPOGs*) within z=0.2. SPOGs* represent 0.2% of the OSSY sample galaxies that
exceed the continuum signal-to-noise cut (and 0.7% of the emission line galaxy
sample). SPOGs* colors suggest that they are in an earlier phase of transition
than OSSY galaxies that meet an E+A selection. SPOGs* have a 13% 1.4GHz
detection rate from the Faint Images of the Radio Sky at Twenty centimeters
survey, higher than most other subsamples, and comparable only to
low-ionization nuclear emission line region hosts, suggestive of the presence
of active galactic nuclei. SPOGs* also have stronger NaD absorption than
predicted from the stellar population, suggestive of cool gas being driven out
in galactic winds. It appears that SPOGs* represent an earlier phase in galaxy
transformation than traditionally selected poststarburst galaxies, and that a
large proportion of SPOGs* also have properties consistent with disruption of
their interstellar media, a key component to galaxy transformation. It is
likely that many of the known pathways to transformation undergo a SPOG phase.
Studying this sample of SPOGs* further, including their morphologies, active
galactic nuclei properties, and environments, has the potential for us to build
a more complete picture of the initial conditions that can lead to a galaxy
evolving.Comment: 19 pages, 19 figures, 3 tables, accepted to ApJ Supplements (Apr 13),
full sample is available on www.spogs.or
Imaging and spectroscopy of galaxies associated with two z~0.7 damped Lyman-alpha absorption systems
We have identified galaxies near two quasars which are at the redshift of
damped Lyman-alpha (DLA) systems in the UV spectra of the quasars. Both
galaxies are actively forming stars. One galaxy has a luminosity close to the
break in the local galaxy luminosity function, L*, the other is significantly
fainter than L* and appears to be interacting with a nearby companion. Despite
the strong selection effects favoring spectroscopic identification of the most
luminous DLA galaxies, many of the spectroscopically-identified DLA galaxies in
the literature are sub-L*, suggesting that the majority of the DLA population
is probably sub-L*, in contrast to MgII absorbers at similar redshifts whose
mean luminosity is close to L*.Comment: 9 pages, to appear in AJ, November 2003 issu
The Spitzer Warm Mission Science Prospects
After exhaustion of its cryogen, the Spitzer Space telescope will still have a fully functioning two-channel mid-IR camera that will have sensitivities better than any other ground or space-based telescopes until the launch of JWST. This document provides a description of the expected capabilities of Spitzer during its warm mission phase, and provides brief descriptions of several possible very large science programs that could be conducted. This information is intended to serve as input to a wide ranging discussion of the warm mission science, leading up to the Warm Mission Workshop in June 2007
Imaging and Spectroscopy of Galaxies Associated with Two z ~ 0.7 Damped Lyα Absorption Systems
We have identified galaxies near two quasars that are at the redshift of damped Lyα (DLA) systems in the UV spectra of the quasars. Both galaxies are actively forming stars. One galaxy has a luminosity close to the break in the local galaxy luminosity function, L*; the other is significantly fainter than L* and appears to be interacting with a nearby companion. Despite the strong selection effects favoring spectroscopic identification of the most luminous DLA galaxies, many of the spectroscopically identified DLA galaxies in the literature are sub-L*, suggesting that the majority of the DLA population is probably sub-L*, in contrast to Mg II absorbers at similar redshifts, whose mean luminosity is close to L*
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