Comet Lovejoy Photobombed by Meteor

We have a new large format camera for the Bucknell Observatory, and I recently tested it on Comet Lovejoy. The reward was a chance appearance of a meteor, visible as a diagonal streak just above the comet.  For reference, the field-of-view is roughly 1/2 degree across, or roughly the width of a full moon.

Two new papers! One by Dinalva Sales et al. (I'm an et al.) on detailed observations of the OH megamaser galaxy IRASF 16399-0937, actually a merger between two galaxies. The other paper is by Billy Vasquez et al. (I'm an et al. again) on infrared/optical reverberation measurements of the active galaxy NGC 6418.

Dinalva and Billy did all the hard work. My main contribution to Dinalva's paper was the introduction of clumpyDREAM, a galaxy SED fitting tool that uses the DREAM(ZS) algorithm (ter Braak and Vrugt 2008). For Billy's paper, I performed the Spitzer Space Telescope infrared measurements.

PHYS 141 Secrets of the Universe - Fall 2014

Course materials are starting to appear on Moodle. The textbook is Kirkpatrick and Francis, 7th ed.

Spitzer Space Telescope IRAC, IRS, and MIPS SED data for the 12 micron Seyfert Sample

I published a paper in 2010 presenting my Spitzer Space Telescope observations of the 12 micron Seyfert Galaxy sample. The paper includes some original data processing to optimize signal-to-noise and reduce artifacts. 

I'm occasionally asked for the data, which I happily share. The easiest way to get to the processed data is via ResearchGate. The spectra can be found at this link, and IRAC images can be found at this link.

Long-Slit Reduction in Python (pt. 2)

Some other projects have taken priority, and I haven't had time to complete my Python data reduction experiment. For anyone interested in trying Python for FITS data reduction, I've placed my incomplete reduction script at this link.

The script includes basic processing steps, including,

• Processing darks and flats,
• Applying dark and flat correction to image data (for a single image),
• Identifying the location of bright lines on arc-lamp images, tracing them along the spatial axis, and applying an interpolation to rectify an image along the wavelength axis. 

What's missing?

• I haven't calculated a wavelength calibration solution based on arc lamp observations.
• I haven't rectified images along the spatial axis.

OH maser detection using WIDAR on the Jansky VLA

OH (hydroxyl) maser galaxies are argued to occur in young quasars. OH masers appear as the quasar heats the surrounding molecular gas.

Masers are the radio wave equivalent of lasers, and they occur naturally in molecules with metastable energy levels; water vapor also produces natural maser emission.

OH masers commonly occur in interacting galaxies, and so it has been difficult to identify unambiguously which of the galaxies is the maser source. In addition, many of the early claims of OH maser detection were never confirmed, or the discovery spectrum was never published.

I'm involved in a project to use the Jansky VLA to observe a sample of OH maser galaxies. The new WIDAR correlator allows us to search a wider range of the radio spectrum. The OH molecule has four spectral lines in the spectral window we selected, although only two of the lines show maser emission strong enough to detect.

The goals of this project are to confirm the presence of OH maser emission and to determine the location of the masers to ~ 1 arcsecond accuracy (1 arcsecond = 1/3600th of a degree). This is my first time using the upgraded VLA, and the spectrum shown above represents the first detection from this project. The maser appears as a pair of closely spaced peaks in the spectrum. For reference, this OH maser galaxy is located at a distance of roughly 3.2 billion light years.

Toward Long-Slit Data Reduction in Python

I recently collected a bunch of long-slit spectroscopy data at the Apache Point Observatory 3.5m telescope. Now, it's been about 20 yrs since I've reduced a long-slit spectrum. I wasn't keen to re-learn IRAF, and so I thought I'd give it a try in Python. I've managed to get as far as correcting the distortion of the wavelength grid based on observations of neon arc lines. The correction is subtle: essentially, in the raw image, an emission line gently curves so that an image column does not map uniquely to a specific wavelength. The correction removes this curvature.

This wavelength grid correction makes sky subtraction a lot easier, and my first results are shown in the figure below. The top panel is a raw spectrum of an active galaxy; actually, if you look closely, you'll see spectra of two galaxies whose nuclei fell within the slit. The spectrum is dominated by sky glow (bright vertical lines). The bottom panel shows the image after the wavelength grid correction, and the sky glow has been subtracted by interpolating over the source. The quality of the sky subtraction has been affected by cosmic ray hits, but it's a good start. To be clear: all work was done in Python with no help from IRAF!