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DATA/RESULTS
**NEW NOV 2014** First Science Results from the LMT
UMASS PRESS RELEASE
Kirkpatrick et al. 2012 High redshift SED templates for star-forming galaxies and AGN based on Spitzer and Herschel data.
GOODS-N 1mm AzTEC+MAMBO combined maps
GOODS-N SCUBA 850 micron maps
smg_midIR.sav* Mid-infrared composite spectrum for submillimeter galaxies from Pope et al. 2008 (ApJ, 675, 1171). Please see this paper for more details.
smg_sed.sav* Composite mid-infrared to radio spectral energy distribution for submillimeter galaxies from Pope et al. 2008 (ApJ, 675, 1171).
Pope08_spectra.tar A tarfile containing the individual mid-IR spectra (as IDL sav files*) for each of the 13 submillimeter galaxies in Pope et al. 2008 (ApJ, 675, 1171).
* For a full description of these files, in IDL type: restore,'filename.sav',/verb
RESEARCH INTERESTS
Galaxy formation and evolution, submillimetre and infrared galaxies, star formation rates, active galactic nuclei, spectral energy distributions, and the cosmic infrared background
How is dust tracing ongoing activity in galaxies and how does it affect the evolution of massive galaxies?
In infrared luminous galaxies, we rely to the dust reradiated light to tell us about the underlying processes, such as star formation and AGN activity, emitting at shorter wavelengths. This requires a detailed knowledge of the properties of the dust such as composition, grain size distribution, mass and emissivity. With the advent of extragalactic surveys with the Spitzer Space Telescope and the Herschel Space Observatory we are now in a position to measure the spectral energy distribution of the dust from mid-IR to submm wavelengths. My research in this area is focused on trying to compare the measured properties of the dust in high redshift (z~2) galaxies to those seen in local galaxies to look for evolution. In past work I have made use of the deepest Spitzer surveys (GOODS Spitzer and FIDEL) and currently I am exploiting the deepest extragalactic Herschel survey (GOODS Herschel). With future LMT/AzTEC surveys, we will be able to probe more than an order of magnitude further down the luminosity function than current facilities allow in order to study the dust properties of typical galaxies that are dominated the cosmic infrared background. Specifically the longer mm wavelengths provide the best probe of the emissivity of the dust, a quantity that is completely unconstrained currently for high redshift galaxies.
How is star formation being fueled at high redshift?
Current theoretical models debate whether continuous cold gas accretion or massive mergers are producing the enhanced SFRs seen in high redshift galaxies. For the most extreme systems such as submillimeter galaxies, observational evidence indicates an ongoing major merger but the precise link between submm emission and merger phase is uncertain. Detailed morphology of both the visible star light and the gas for this systems exists for only a few sources. The multi-cycle HST treasury program CANDELS (PI Faber) will provide very deep rest-frame optical (for z~2 galaxies) images in several bands at high enough resolution to resolve the individual components of a major merger even for systems enshrouded by dust. Coupled with high resolution imaging with ALMA, I am interested in determining the relationships and interactions between stars, gas and dust during the merger cycle. This will provide insight into the relative role of the external gas supply (cold flows) and mergers in forming the stars in massive galaxies.
In addition to imaging, spectroscopy (CO measurements) is needed to constrain the properties of the gas such as mass and excitation. There appears to be a dichotomy in the star formation efficiencies (star formation per amount of gas) of high redshift galaxies which may also be caused by two modes of star formation; mergers and continuous gas accretion. The excitation of the molecular gas can tell you about the current state of the galaxy. I have been involved in several programs (IRAM PdBI, CARMA) to observe the CO emission in high redshift galaxies to determine what the gas properties tell us about how the gas is fueling the star formation. With current facilities samples are small but in the near future with ALMA and the LMT/redshift receiver, CO measurements can be made for statistical samples of high redshift systems spanning a range of properties to address these issues.
What is the relative role of AGN activity and star formation in dusty high redshift galaxies?
Due to the locally observed M-sigma relation, the buildup of black holes in galaxies is expected to be linked to the buildup of stellar mass. We see evidence for AGN activity in dusty high redshift galaxies that are also undergoing intense star formation but multi-wavelengths indicators of these processes are inconsistent. This indicates that the complex geometry and dust distribution in galaxies is confusing our census of these processes as a function of wavelength. One approach to this problem is to combine indicators of AGN and SF across the electromagnetic spectrum to trace out how the AGN is influencing the host galaxy and ongoing star formation and vice versa. My research in this area is focused on using mid-IR spectroscopy (Spitzer IRS) to determine how much the AGN is influencing the dust emission in order to account for its contamination in determining quantities such as the SFR and dust temperature from the IR data. I have worked on combining the mid-IR indicators with those from deep X-ray imaging to extend the picture. In the future I plan to extend to shorter wavelengths to see what regions of the galaxy we are proving with near-IR spectroscopy where many additional AGN diagnostic lines are found in high redshift galaxies.
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