Rao S.M.,University of Pittsburgh |
Sardane G.,University of Pittsburgh |
Turnshek D.A.,University of Pittsburgh |
Thilker D.,Johns Hopkins University |
And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013
We present Hubble Space Telescope Cosmic Origins Spectrograph spectra of 10 quasars located behind M31, selected to investigate the properties of gas associated with its extended disc and high-velocity clouds (HVCs). The sightlines have impact parameters ranging between b = 13 and 112 kpc. No absorption is detected in the four sightlines selected to sample any extended disc (or halo) gas that might be present in the outer regions of M31 beyond an impact parameter of b > 57 kpc. Of the six remaining sightlines, all of which lie at b < 32 kpc and within the NHI = 2 × 1018 cm-2 boundary of the HI disc of M31, we detect low-ionization absorption at M31 velocities along four of them (three of which include MgII absorption). We also detect MgII absorption from an HVC. This HVC sightline does not pass through the 21 cm disc of M31, but we detect additional MgII absorption at velocities distinct from the HVC that presumably arises in the halo.We find that along sightlines where both are detected, the velocity location of the low-ion gas tracks the peak in 21 cm emission. High-ionization absorption is detected along the three inner sightlines, but not along the three outer sightlines, for which C IV data exist. As inferred from high-resolution 21 cm emission-line maps of M31's disc and extended regions, only one of the sightlines may be capable of harbouring a damped Lyα system, i.e. with NHI ≥ 2 × 1020 cm-2. This sightline has impact parameter b = 17.5 kpc, and we detect both low- and high-ion absorption lines associated with it. The impact parameters of our observed sightlines through M31 are similar to the impact parameters of galaxies identified with MgII absorbers at redshifts 0.1 < z<1.0 in a 2011 study by Rao et al. However, even if we only count cases where absorption due to M31 is detected, the Mg II λ2796 rest equivalent width values are significantly smaller. In comparison, moderate-to-strong MgII absorption from Milky Way gas is detected along all 10 sightlines. Thus, this study indicates that M31 does not present itself as an absorbing galaxy which is typical of higher-redshift galaxies inferred to give rise to moderate-strength quasar absorption lines. M31 also appears not to possess an extensive large gaseous cross-section, at least not along the direction of its major axis. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Khare P.,Inter-University Center for Astronomy and Astrophysics |
Daniel V.B.,St. Vincents College |
Rahmani H.,Institute for Research in Fundamental Sciences |
York D.G.,University of Chicago
Astrophysical Journal | Year: 2014
We studied dust reddening and [O II] emission in 1730 Mg II associated absorption systems (AAS; relative velocity with respect to QSOs, ≤3000 km s-1; in units of velocity of light, β, ≤0.01) with 0.4 ≤z abs≤ 2 in the Sloan Digital Sky Survey DR7, focusing on their dependence on the radio and other QSO properties. We used control samples, several with matching radio properties, to show that (1) AAS in radio-detected (RD) QSOs cause 2.6 ± 0.2 times higher dust extinction than those in radio-undetected (RUD) ones, which in turn cause 2.9 ± 0.7 times the dust extinction in the intervening systems; (2) AAS in core-dominated QSOs cause 2.0 ± 0.1 times higher dust extinction than those in lobe-dominated QSOs; (3) the occurrence of AAS is 2.1 ± 0.2 times more likely in RD QSOs than in RUD QSOs and 1.8 ± 0.1 time more likely in QSOs having black holes with masses larger than 1.23 × 109M ⊙than in those with lower-mass black holes; and (4) there is excess flux in [O II]λ3727 emission in the composite spectra of the AAS samples compared with those of the control samples, which is at the emission redshift. The presence of AAS enhances the O II emission from the active galactic nucleus and/or the host galaxy. This excess is similar for both RD and RUD samples and is 2.5 ± 0.4 times higher in lobe-dominated samples than in core-dominated samples. The excess depends on the black hole mass and Eddington ratio. All these point to the intrinsic nature of the AAS except for the systems with z abs> z em, which could be infalling galaxies. © 2014. The American Astronomical Society. All rights reserved.
Gahr S.A.,St. Vincents College |
Weber G.M.,U.S. Department of Agriculture |
Rexroad III C.E.,U.S. Department of Agriculture
Fish Physiology and Biochemistry | Year: 2012
The Smad proteins are essential components of the TGF-β/activin/nodal family signaling pathway. We report the identification and expression of transcripts representing three receptor Smads (Smad2a, Smad2b, and Smad3), two common Smads (Smad4a and Smad4b), and one inhibitory Smad (Smad7). Phylogenetic analysis suggests this gene family evolved through the combination of ancient and more recent salmonid genome duplication events. Tissue distribution, embryonic expression, and expression in growth hormone (GH) treated fish were assessed by reverse transcription PCR or qPCR. All six Smad transcripts were ubiquitously expressed in adult tissues. We observed the highest expression of the receptor Smads in unfertilized eggs, generally decreasing during early embryonic development and slightly increasing around 11 days post-fertilization (dpf). Smad7 expression was low for most of embryonic development, with a dramatic increase at the onset of muscle development (6 dpf), and at hatch (24 dpf). Smad4 expression was low during early embryonic development and increased after 14 dpf. The increased expression of Smad4 and Smad7 during late embryonic development may indicate modulation of gene expression by GH axis, which initiates activity during late embryonic development. These data were supported by the modulation of these Smads in the gill filament, stomach, and muscle following a GH treatment. Additionally, these changes are concurrent with the modulation of expression of TGF-β family members. Most significantly, the increased expression of Smad7 in the muscle is simultaneous with increased expression of MSTN1A and not MSTN1B during both embryonic development and following GH treatment. These data indicate a promyogenic role for Smad7 as previously identified in other non-fish species. © 2012 Springer Science+Business Media B.V.
Hoversten E.A.,Pennsylvania State University |
Gronwall C.,Pennsylvania State University |
Vanden Berk D.E.,St. Vincents College |
Basu-Zych A.R.,NASA |
And 6 more authors.
Astronomical Journal | Year: 2011
We present Swift UV/Optical Telescope (UVOT) imaging of the galaxies M81 and Holmberg IX. We combine UVOT imaging in three near-ultraviolet (NUV) filters (uvw2: 1928 Å ; uvm2: 2246 Å ; uvw1: 2600Å ) with ground-based optical imaging from the Sloan Digital Sky Survey to constrain the stellar populations of both galaxies. Our analysis consists of three different methods. First, we use the NUV imaging to identify UV star-forming knots and then perform spectral energy distribution (SED) modeling on the UV/optical photometry of these sources. Second, we measure surface brightness profiles of the disk of M81 in the NUV and optical. Lastly, we use SED fitting of individual pixels to map the properties of the two galaxies. In agreement with earlier studies, we find evidence for a burst in star formation in both galaxies starting ∼200Myr ago coincident with the suggested time of an M81-M82 interaction. In line with theories of its origin as a tidal dwarf, we find that the luminosity-weighted age of Holmberg IX is a few hundred million years. Both galaxies are best fit by a Milky Way dust extinction law with a prominent 2175 Å bump. In addition, we describe a stacked median filter technique for modeling the diffuse background light within a galaxy and a Markov chain method for cleaning segment maps generated by SExtractor. © 2011. The American Astronomical Society. All rights reserved.
Urick M.J.,St. Vincents College
Journal of Intergenerational Relationships | Year: 2014
While interest in intergenerational phenomena has been growing in organizations, academic research in the field of organizational studies has questioned the existence of generational differences. However, despite this questioning, generational stereotypes are known and enacted in the workplace. Using a dramaturgical approach as suggested by Goffman (1959), the purpose of this theory article is to advocate a simple model of generational stereotype reinforcement in organizations in which individuals enact (or do not enact) prototypical generational traits and behaviors when doing so allows them to appear in a positive light to a particular generational group. © , Copyright © Taylor & Francis Group, LLC.