arXiv subjects

J. Darling

Publications and source records attributed to J. Darling.

21 records · Page 2Linked to original sources

arXiv2004

High-resolution Imaging of the OH Megamaser Emission in IRAS12032+1707 and IRAS14070+0525

We present results from VLBA observations of the 1667 and 1665 MHz OH lines in the two OH megamaser galaxies IRAS12032+1707 and IRAS14070+0525. For IRAS12032+1707 we also present Arecibo HI absorption data. Almost all OH emission previously detected by single dish observations has been recovered in IRAS12032+1707 and is found on a compact scale of <100 pc. The emission shows an ordered velocity field that is consistent with a single disk. However, the data is also consistent with a scenario including two physically different gas components. We explore this possibility, in which the two strongest and most blueshifted maser features are identified as the tangent points of a circumnuclear torus. The redshifted maser features would be extended in a direction perpendicular to the torus, which is in the direction of the merger companion. Thus, redshifted emission could be associated with an inflow triggered by a tidal interaction. HI absorption covers the velocities of the redshifted maser emission, suggesting a common origin. In the second source, IRAS14070+0525, a large fraction of the OH emission is resolved out with the VLBA. We find no significant evidence of an ordered velocity field in this source, but these results are inconclusive due to a very low signal-to-noise ratio.

astro-ph↗

arXiv2003

Peculiar Broad Absorption Line Quasars found in DPOSS

With the recent release of large (i.e., > hundred million objects), well-calibrated photometric surveys, such as DPOSS, 2MASS, and SDSS, spectroscopic identification of important targets is no longer a simple issue. In order to enhance the returns from a spectroscopic survey, candidate sources are often preferentially selected to be of interest, such as brown dwarfs or high redshift quasars. This approach, while useful for targeted projects, risks missing new or unusual species. We have, as a result, taken the alternative path of spectroscopically identifying interesting sources with the sole criterion being that they are in low density areas of the g - r and r - i color-space defined by the DPOSS survey. In this paper, we present three peculiar broad absorption line quasars that were discovered during this spectroscopic survey, demonstrating the efficacy of this approach. PSS J0052+2405 is an Iron LoBAL quasar at a redshift z = 2.4512 with very broad absorption from many species. PSS J0141+3334 is a reddened LoBAL quasar at z = 3.005 with no obvious emission lines. PSS J1537+1227 is a Iron LoBAL at a redshift of z = 1.212 with strong narrow Mgii and Feii emission. Follow-up high resolution spectroscopy of these three quasars promises to improve our understanding of BAL quasars. The sensitivity of particular parameter spaces, in this case a two-color space, to the redshift of these three sources is dramatic, raising questions about traditional techniques of defining quasar populations for statistical analysis.

astro-ph↗

arXiv1999

A Search for OH Megamasers at z > 0.1: Preliminary Results

We report the discovery of 11 OH megamasers and one OH absorber, along with upper limits on the OH luminosity of 53 other luminous infrared galaxies at z > 0.1. The new megamasers show a wide range of spectral properties, but are consistent with the extant set of 55 previously reported objects, 8 of which have z > 0.1. The new OH detections are the preliminary results of a OH megamaser survey in progress at the Arecibo Observatory, which is expected to produce several dozen detections and calibrate the luminosity function of OH megamasers to the low-redshift galaxy merger rate (0.1 < z < 0.2).

astro-ph↗