stoll at astronomy dot ohio-state dot edu
Department of Astronomy
The Ohio State University
140 W 18th Avenue
Columbus, OH 43210
We define a conversion from oxygen abundance to iron abundance by using the observed stellar abundances of stars in the Milky Way bulge, disk, and halo with a wide range of metallicities, finding the median [Fe/H] of type II progenitor regions is between -0.60 and -0.39, depending on the value of the solar oxygen abundance.
Electronic versions of the data tables in the paper can be found here.
ADS --- arXiv:1205.2338
Core-collapse supernovae (associated with massive stars) are generally much less luminous than type Ia supernovae (associated with white dwarfs), but recently core-collapse SNe have been discovered which are not only more luminous than normal type II-P SNe, but are even more luminous than type Ia SNe. The host galaxy luminosities of imply that they are on the low end of the galaxy mass distribution, and are expected by the mass-metallicity relation to be metal-poor (Drake et al. 2010, Neill et al. 2011).
Working with Jose Prieto, Kris Stanek, Rick Pogge, and others, I demonstrated that this expectation is borne out by examining the gas-phase metallicity of the progenitor regions of several of these events (the blue and green points above), and found that they appear to be at the extreme low end of the galaxy metallicity distribution (contours from Tremonti et al. 2004, converted to a common metallicity scale.)
ADS --- arXiv:1012.3461 --- preprint (PDF, 410 Kb)
The Ohio-State Multi-Object Spectrograph, or OSMOS, is a high-efficiency imager and spectrograph with low- and medium-resolution capability that will be one of the primary facility instruments at the Hiltner 2.4 m at MDM observatory. OSMOS can accomodate up to five dispersers at a time. Its complement currently includes a very low resolution triple prism and a low-resolution volume-phase holographic (VPH) grism. OSMOS was commissioned in April 2010.
Paul Martini is the instrument PI. The team also includes Rick Pogge, mechanical engineer Mark Derwent, optical engineer Ross Zhelem, electrical engineer Dan Pappalardo, software specialist Ray Gonzalez, and undergraduate Man-Hong Wong. I worked on several aspects of the instrument, including designing and constructing the electronics assembly, aided by Brandyn Ward and guided by Dan Pappalardo. I also aided in final assembly, testing, and commissioning.
(SPIE requires me to post this with the paper: DOI: 10.1117/12.857893 Copyright 2010 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.)
Mechanisms and Instrument Electronics for the Ohio State Multi-Object
Stoll, R., Martini, P., Derwent, M. A., Gonzalez, R., O'Brien, T. P., Pappalardo, D. P., Pogge, R. W., Wong, M.-H., Zhelem, R. 2010, Proc. SPIE
preprint (PDF, 864 Kb)
The OSU filter wheel has several advantages over the old MDM system. It accomodates more and larger filters. The four-inch filters can be rapidly repositioned during observing, their positions are very repeatable, and it is simple to swap out filters if an extraordinary observing program requires more than twelve filters a night.
In 2008, Smita Mathur and I worked on extrapolating location information for the X-ray warm absorber around a Seyfert II to outflows observed in the UV in the spectra of other low-luminosity AGN. The point was to determine whether these UV outflows would be useful sources of feedback or not. We found that in general the outflows have low velocities compared with the escape velocity at their location.
Interpreting this result is not as straightforward as it might seem. Because the potential is still dominated by the black hole and not the galactic potential at these locations, the consequences of these findings for the efficacy of these outflows as sources of feedback is entirely dependent on the wind model; acceleration may very well still be efficient if the outflows are line-driven. The geometry may be complex. The duty cycle may be small. Feedback is not expected to be efficient for Seyferts. Nevertheless, it is a useful addition to our growing knowledge about various kinds of AGN outflows.
We do find a weak but significant correlation between the ratio of outflow velocity to escape velocity and AGN continuum luminosity. This result is independent of wind models.
ADS --- arXiv:0903.5310
One way to investigate the merger dependence is to examine the environments. I compared the 10-100 kpc environments of each of the 540 of these objects in SDSS DR3 to a comparison sample of AGN matched in redshift and luminosity. We did not apply a redshift cut for the neighbors, both to preserve faint objects and to obviate the problem of fiber collisions, relying instead on large number statistics to tease out effects. I found no significant difference in number or color of neighbors or distance of nearest neighbor between normal AGN and AGN with a substantial population of young stars.
This work was done in 2005-2007, but the intent is to publish it in combination with information on the nearer environments of PSQs, work done by Sabrina Cales, which is still in progress.