I plan to show a scientific snapshot of my work here from time to time. This is some of our recent work on the properties of molecular gas in the highest redshift submillimeter galaxy (SMG). See Riechers et al. (2010
) for details.
Sub-millimeter galaxies (SMGs) are massive, gas-rich galaxies in the early Universe that undergo the most intense, typically dust-enshrouded star formation events. Since their initial discovery little more than a decade ago, substantial observational and theoretical efforts have gone into determining the key physical properties of these enigmatic systems, and to unravel their role in cosmic star formation and the assembly of the most massive present day galaxies as a whole.
Following our recent discovery of a SMG at an unprecedented redshift of z=5.3, only 1.1 billion years after the Big Bang, we have used the new capabilities of the Expanded Very Large Array (EVLA) and the Plateau de Bure interferometer (PdBI) to detect CO 2-1, 5-4, and 6-5 emission from its molecular gas reservoir. Our observations of this most distant SMG, dubbed AzTEC-3, ultimately confirm the large cosmological distance, making it the most submillimeter-luminous galaxy in a massive z = 5.3 protocluster structure in the COSMOS field.
Enabled by the new EVLA 0.9 cm band, the unprecedented spectral resolution and wavelength coverage of the new EVLA WIDAR correlator, and the recent PdBI correlator upgrade, we were able to study the gas reservoir in this highest redshift SMG in considerable detail. The strength of the CO line emission reveals a large molecular gas reservoir with a mass of 53 billion times the mass of the Sun, which can maintain the intense starburst of 1800 solar masses per year in this system for at least 30 million years, increasing the stellar mass by up to a factor of six in the process.
This gas mass is comparable to typical z~2 SMGs in the peak epoch of cosmic star formation, and constitutes approximately 80% or more of the baryonic mass (gas + stars) and more than 30% of the total mass in this galaxy. The molecular gas reservoir has a radius of less than 4 kiloparsecs and likely consists of a diffuse component, containing at least 1/3 of the gas mass, and a dense component, containing up to 2/3 of the mass. The likely presence of a substantial diffuse gas component besides dense gas suggests different properties between the star-forming environments in z>4 SMGs and z>4 quasar host galaxies (which we targeted in previous studies with the Very Large Array and Green Bank Telescope), perhaps signifying different stages in the evolution of massive galaxies (early and late, respectively).
The discovery of a massive, metal-enriched gas reservoir in a SMG at the heart of a large z=5.3 protocluster considerably enhances our understanding of early massive galaxy formation, pushing back to a cosmic epoch where the Universe was less than 1/12 of its present age.
See Riechers et al. (2010
) for details.