Hubble Ultra Deep Field, NASA
Alexandra Pope
Professor
University of Massachusetts Amherst
Illuminating the Dusty Side of Galaxy Growth
I am interested in understanding the formation and evolution of galaxies over cosmic time. Several billion years after the beginning of the Universe, galaxies experienced a growth spurt consisting of rapid star formation and black hole growth. This peak period of galaxy growth created roughly half the stars in the present-day Universe. As shown in this figure, most of the activity occurs in dusty galaxies where infrared (IR) and (sub)millimeter (mm) observations reveal the hidden star formation and black hole growth. At earlier times in the Universe, we are finding galaxies ~500 million years after the Big Bang with the Hubble Space Telescope (HST), but the role of dust-obscured activity in the early Universe is unknown. An outstanding question in galaxy evolution is how the Universe builds up metals and dust. Data for this figure is from Murphy et al. (2011), and Bouwens et al. (2009).
With the next generation of IR and (sub)mm telescopes (such as the Large Millimeter Telescope, LMT), we are now in a position to push below the ULIRG regime and directly detect the dust and gas in galaxies which dominate the cosmic star formation and black hole growth. The LMT is a partnership between UMass Amherst and the country of Mexico. This figure shows the limiting IR luminosity as a function of redshift from the deepest Herschel surveys (blue curves) and what we can obtain with the AzTEC camera on a 32 and 50m LMT (red curves).
The past two years, we completed Early Science observations at the LMT. My group has been actively involved in many observing programs including (but not limited to) RSR observations to quantify the molecular gas in intermediate redshift AGN and star-forming galaxies (Kirkpatrick, Pope, et al. 2014), RSR observations to obtain redshifts of dusty galaxies (e.g. Yun et al. 2015), an AzTEC survey of the HST Frontier Fields (Pope et al. 2017, Montana et al. in prep.), and an AzTEC survey of the CANDELS fields (ongoing).
Stay tuned for more papers coming!
Until recently, surveys of high redshift dust-obscured activity were limited to small areas of the sky, and only detected the bright ultra-luminous infrared galaxies (ULIRGs, log(LIR[L⊙]) > 12), most of which are found to be at z ∼ 1–4. However, much of the cosmic star formation activity is occurring in lower luminosity galaxies which have been identified in deep ultraviolet (UV) surveys. Even though these galaxies are selected at UV wavelengths, most of their star formation activity is being obscured by dust; we have yet to directly detect this activity in the IR. We require direct observations of the dust emission in typical star-forming galaxies at high redshift in order to complete the census of dust-obscured activity in our Universe.