I am currently a Hubble Fellow at Caltech. Most of my work has revolved around the observational study of gamma-ray bursts, their afterglows, and their host galaxies. I have been involved extensively with afterglow follow-up using the robotic telescopes KAIT and PAIRITEL as well as with spectroscopy on large-aperture telescopes Keck and Gemini; the focus of my thesis work involves host-galaxy observations: searching for and cataloguing the properties of the galaxies in which GRBs have occurred. Since the average redshift of a gamma-ray burst is about z=2.0, this means looking at extremely distant and faint galaxies, observed at a time when the universe was about half its present age. My current research interests focus on the GRB-dust connection: probing the properties of high-redshift dust using GRBs, and understanding the selection biases dust imposes on the existing GRB afterglow sample.
Some particular research questions I've been interested in:
- What is the origin of 'dark' gamma-ray bursts, GRBs without optical afterglow? Are their host galaxies fundamentally different from normal GRBs?
- How can GRBs inform our understanding of the nature of dust extinction in high-redshift star-forming galaxies: both its abundance and its wavelength dependence?
- Can GRBs be used to trace star formation in places not well-probed by more traditional survey techniques, such as intergalactic space, dusty clouds, or highly underluminous galaxies?
- Observationally, how can we constrain and inform the various theoretical models of "short" gamma-ray bursts?
- Are there rare classes of, or production channels for, GRBs beyond the simple two-class (short/long) model? How can we improve our understanding of these events?
- Do genuine long GRBs sometimes fail to produce supernovae?
- What is the origin and frequency of magnetar hyperflares?
Select list of publications:
- Perley, Morgan, Updike et al. (2010): "Monster in the Dark: The Ultraluminous GRB 080607 and its Dusty Environment"
The second most luminous GRB on record (at optical/UV wavelengths) occurred behind a dark molecular cloud at a redshift of z=3, offering a nearly perfect opportunity to study the dust properties of an event in the early universe. We show that the dust extinction curve is quite similar to local templates and place this GRB in the context of other events, like GRB 080319B.
- Perley, Bloom, Klein et al. (2010): "Evidence of Supernova-Synthesized Dust from the Afterglow of GRB 071025 at z=5"
The highest-redshift PAIRITEL-detected burst to date, dating to only 1.3 billion years after the Big Bang, was obscured by dust with an unusual extinction law indicative of silicate and other compounds formed by previous supernovae in that galaxy. By comparison, dust in the modern universe is thought to have been formed by red giant stars.
- Perley, Cenko, Bloom et al. (2009): "The Host Galaxies of Swift Dark Gamma-Ray Bursts: Observational Constraints on Highly Obscured and Very High-Redshift GRBs"
Here we examine a subsample of our host observations with uniform, deep early optical afterglow coverage from the P60 robotic telescope. Almost every "dark" event has a detectable host, ruling out the high redshift scenario as a predominant cause of dark bursts. We instead favor host-galaxy dust extinction (up to 5-10 magnitudes in some cases) as the predominant cause of dark bursts.
- Perley, Metzger, Granot et al. (2009): "GRB 080503: Implications of a Naked Short Gamma-Ray Burst Dominated by Extended Emission"
(ApJ 696:1871 2009)
This bright short gamma-ray burst showed one of the faintest afterglows on record, suggesting it had exploded in a near-vaccuum, in accordance with predictions of short gamma-ray bursts being ejected from their host galaxies. At the same time, the puzzling nature of its gamma-ray light curve poses theoretical difficulties for some of the leading models.
- Prochaska, Sheffer, Perley et al. (2009): "The First Positive Detection of Molecular Gas in a GRB Host Galaxy"
(ApJ 691:27 2009)
A phenomenal burst at a redshift of z=3 that fortuitously occurred while we were at Keck showed features that the community had been seeking for over a decade: molecular lines (in addition to hundreds of ionic lines). By combining the Keck spectrum with optical and infrared afterglow follow-up we were also able to constrain the dust properties and report a secure detection of the locally ubiquitous 2175-Angstrom dust feature.
- Bloom, Perley, Li et al. (2008): "Observations of the Naked-Eye GRB 080319B: Implications of Nature's Brightest Explosion"
(ApJ 691:723 2009)
GRB 080319B is the brightest and most optically luminous gamma-ray burst ever observed and has perhaps the best early data-set to date of any gamma-ray burst. We followed the burst starting from 1 minute and until many months after the burst, interpreting its unusual light curve and discussing implications for the observability of GRBs in the distant universe.
- Perley, Li, Chornock et al. (2008): "GRB 071003: Broadband Follow-up Observations of a Very Bright Gamma-Ray Burst in a Galactic Halo"
(ApJ 688:470 2008)
One of the brightest bursts that year, this event displayed several puzzling features including a dramatic late-time rebrightening and, most curiously, almost no sign of absorption from its host galaxy. No host galaxy was identified at the burst location. This burst either occurred in an extremely small galaxy or in a halo, perhaps in a tidal tail.
- Perley, Bloom, Butler et al. (2008): "The Troublesome Broadband Evolution of GRB 061126: Does a Gray Burst Imply Gray Dust?"
(ApJ 672:449 2007)
This extremely bright gamma-ray burst had among the best early broad-band coverage for any event, with simultaneous, highly precise measurements from the UV (2000 Angstroms) to IR (20000 Angstroms) plus X-ray follow-up. Surprisingly, relative to the X-ray the optical band appears strongly extinguished, but hardly reddened at all, suggesting the possible need for "gray" dust. This burst is probably the best example to date of this phenomenon.
Many additional publications are available via ADS below.
A list is also available in my CV.