I am an associate professor
in the Dept. of Astronomy and the Dept. of Physics at the University
of Florida. My research is focussed on the origin of planets, stars, galaxies
and black holes, and involves both theoretical and observational
THE FIRST STARS
Starting at high redshift, I am interested in the formation of the very
first stars. With my collaborators, using a combination of analytic
and numerical models I am trying to predict the initial mass function
of these objects and address whether they can be the seeds for
supermassive black holes. You can read a summary of this work
in Tan & McKee (2008) and see the following papers for
Tan & McKee (2004); Tan & Blackman (2004); McKee & Tan (2008); Natarajan, Tan & O'Shea (2009); Banik, Tan & Monaco (2016).
GALAXIES & STARBURSTS
On galactic scales I am working on understanding the physical process
that govern the large scale conversion of gas into stars in disk
galaxies and circumnuclear starbursts. I have advanced a theory
(Tan 2000) that shear-driven GMC collisions
(i.e. colliding molecular flows) play an important role in this
also Tasker & Tan (2009), Tan (2010), Suwwanajak, Tan & Leroy (2014).
Locally star formation is localized in molecular gas, but it is
generally a very inefficient process. Understanding the dynamics and
evolution of giant molecular clouds is crucial for a more fundamental
understanding of star formation on galactic as well as star cluster
scales. See Tan, Shaske & Van Loo (2013) for a recent review.
STAR CLUSTER FORMATION
On the scale of star clusters, with my
collaborators Chris McKee and Mark Krumholz, I have proposed that
(massive, rich) star cluster formation is a slow, quasi-equilibrium
process, in the sense that the gas takes at least several free-fall
times to complete its star formation
(Tan, Krumholz & McKee 2006). Protostellar outflows
are thought to be responsible for supporting the gas over these
also Krumholz & Tan (2007) for discussion of the star
formation rate per free-fall
time. See Tan (2007) for a brief review. We have consider the
structure, dynamics and star formation rate of the Orion Nebula
Cluster in Da Rio, Tan & Jaehnig (2014), and the structural evolution
of a sample of Galactic clusters in Jaehnig, Da Rio & Tan (2014).
MASSIVE STAR FORMATION
For a recent review see Tan et al. (2014).
For individual massive star formation, with Chris McKee, I have
developed the Turbulent Core Model
(McKee & Tan
2002; McKee & Tan 2003), which describes the process as a
scaled-up version of standard low-mass star formation theory from gas
cores, but now with most of the pressure support being due to a
combination of turbulence and magnetic fields rather than thermal
pressure. Bipolar outflows will help control the spread of ionizing
feedback (Tan & McKee 2003). Astrochemical implications have
by Doty, van Dishoeck & Tan (2006) and
application to the Orion Nebula Cluster by Tan (2008). To help test the model by searching for the initial conditions of massive starless cores, we have developed a Mid-IR Extinction Mapping Technique (Butler & Tan 2009; Butler & Tan 2012 ) and are involved in numerous observational studies of massive star-forming regions. We have reported a detection and analysis of massive starless cores in Tan et al. (2013). We have presented radiative transfer models of massive star formation in Zhang & Tan (2011), Zhang, Tan & McKee (2013), Zhang, Tan & Hosokawa (2014)
We (Chatterjee & Tan 2014) have proposed the Inside-Out Planet Formation model, which attempts to explain the existence of the many closely packed transiting planetary systems discovered by Kepler as resulting from sequential planet formation from pebble rings at inner dead zone boundaries.
STAR FORMATION NEAR SUPERMASSIVE BLACK HOLES
For accretion disks around supermassive black holes, with my
collaborators, in particular Eric Blackman and Jeremy Goodman, I have investigated
various consequences of star formation. These include the possibility that
star formation is major mass sink from the accretion disk, even in
low-accretion rate systems like giant elliptical galaxies (Tan & Blackman 2005; Tan, Beuther, Walter & Blackman 2008), and the
possiblilty of super-massive star formation (Goodman & Tan 2004).
GAMMA RAY BURSTS FROM SUPERNOVAE
Building on an idea originally proposed by Stirling Colgate, with
Chris Matzner and Chris McKee, I developed the Transrelativistic
Supernova Blastwave model to explain how relativistic ejecta can be created as a shock breaks out of a star (Tan, Matzner & McKee 2001). This ejecta then produce gamma ray emission that may explain certain types of Gamma Ray Bursts. See also Munoz & Tan (2005).
The theoretical components of these projects generally involve the
development of analytic theories in combination with numerical
simulation experiments. For the latter, we typically make use of
adaptive mesh refinement codes and are including the effects of
The observational components of the
above projects involve a wide variety of projects. My collaborators
and I have taken and analyzed data from many telescope facilities,
including: Chandra, XMM-Newton, VLA, VLT, AAT, Gemini, APEX, CSO, SMA,
JCMT, IRAM 30m, GBT and Mopra. In particular, our group in Florida is
leading a number of studies on Infrared Dark Clouds and a large,
complete census of dense gas in the Southern Milky Way
(The Census of High and Medium-Mass Protostars -
CHaMP). I am a member of the instrument science
team of IRIS (Thirty Meter
Telescope). I am a Co-Investigator
of Hi-GAL: the Herschel Infrared Galactic Plane Survey. I am PI of the SOfia MAssive star formation (SOMA) Survey with SOFIA - Stratospheric Observatory for Infrared Astronomy to study massive protostars. Our group has led 12 approved ALMA proposals so far (through Cycle 4). I am PI of several approved Chandra programs to study Infrared Dark Clouds and young star clusters. I am co-PI (with Kevin Covey) of the SDSSIII APOGEE Ancillary Science Project: INfrared Spectroscopy of Young Nebulous Clusters (IN-SYNC). Our group is leading several HST projects to study young star clusters and massive protostars.
Graduate and undergraduate students interested in research projects should feel free to contact me by email or stop by my office (302 Bryant).
In 2006 we started the Theoretical Astrophysics Postdoctoral Fellowship Program here at UF. We have had the following postdoctoral fellows in the program: Elizabeth Tasker (2006-2009); Matthew Payne (2009-2012); Aaron Boley (2009-2012); Sven Van Loo (2009-2011); Cosimo Fedeli (2010-2013); Sourav Chatterjee (2010-2014); Nicola Da Rio (2013-); Kei Tanaka (2014-); Duncan Christie (2015-); Jan Staff (2015-2016); Thomas Bisbas (2016-). If you are interested in theoretical astrophysics postdoctoral opportunities at UF please contact me.
Florida Star Formation Conference Series: In 2007 we organized the 140 person meeting, From Stars to Planets, with the aim of linking the star and planet formation communities. We continued this series in 2010 with the 220 person meeting, From Stars to Galaxies, which is one of the largest star and galaxy formation meetings this year. The third conference in the series was From Stars to Life - Connecting our understanding of star formation, planet formation, astrochemistry and astrobiology. The fourth meeting is From Stars to Massive Stars - Connecting our understanding of massive star & star cluster formation through the universe.
We also organize the ASTROWIN
and Florida Star and Planet Formation Days workshops.
I was a member of the Planetary Systems and Star Formation Panel of the Astro2010 Decadel Survey.
I am a member of the SOFIA Users Group - feel free to contact me if you have input about the use of this facility.
Some Recent Press Releases:
How Do Strange, Scorching-Hot 'Vulcan Planets' Form?
Planets Formed Close to Their Stars Are Named for Vulcan, the Roman God of Fire
Fortifying the Brick and Charming the Snake
The Darkest Shadows with Spitzer
Massive Starless Cores with ALMA
Massive Star Formation with SOFIA
Selected Research Funding (as PI):
NSF CAREER (2007) - Massive Star & Star Cluster Formation - the key to our origins
NASA SIM Science Studies (2008) - Stellar Dynamical Processes in Massive Star and Star Cluster Formation
NSF REU Supplement (2009)
NASA Astrophysics Theory and Fundamental Physics (2010) - The Galactic Star Formation Hierarchy
NASA Outreach Supplement (2010)
NASA Astrophysics Data Analysis (2011) - Shadows and Dust - Mid-Infrared Extinction Mapping of the Initial Conditions of Massive Star and Star Cluster Formation
NSF Astronomy & Astrophysics Grants Program (2012) - The Mass of the First Stars and Black Holes
Florida Space Inst. (2013) - Astrophysics and Astrochemistry of Habitable Planet Formation
NSF Astronomy & Astrophysics Grants Program (2013) - Molecular Mountains of the Milky Way
NSF Astronomy & Astrophysics Grants Program (2014) - Astrophysical and Astrochemical Tests of Massive Star Formation Theories
NASA Astrophysics Data Analysis (2015) - Far-Infrared Extinction Mapping: a window to the darkest depths
NASA Astrophysics Theory (2015) - Inside-Out Planet Formation
NSF Astronomy & Astrophysics Grants Program (2016) - Collaborative Research: Pebbles and Gas - The Supply Chain for Compact Planetary Systems