Molecular observations of the high redshift universe

Molecular gas plays an important role in the evolution of galaxies, formation of stars and planets, and the complex prebiotic molecules are the basis for life. My dissertation focuses on the molecular emission from Dusty Star Forming Galaxies (DSFGs) at high redshift to study the interstellar medium (ISM) conditions in the early universe. Molecular hydrogen (H2) is the fuel for star formation and is the most abundant molecule in the universe. However, it is difficult to observe due to the lack of a permanent dipole moment. The next most abundant molecule is carbon monoxide (12C16O or CO) which is used as a tracer for diffuse molecular gas in the ISM. Water (H2O) is the third most abundant molecule and can be as bright as mid-J CO. The mid-J H2O transitions are excited due to infrared pumping and are found to trace the infrared field over several orders of magnitude of luminosity both in the local and high redshift universe. The analysis from this dissertation was published in The Astrophysical Journal: Jarugula et al. (2019) and Jarugula et al. (2021). DSFGs, which are invisible in optical but bright in far-infrared, play an important role in the cosmic stellar assembly. Galaxy evolutionary models suggest that DSFGs are the progenitors of the present day massive ellipticals. It is therefore important to study the high redshift population of these galaxies in the context of stellar assembly and galaxy evolution. The sources of interest in the dissertation are the DSFGs selected from the South Pole Telescope (SPT) survey. Most of the SPT submillimeter galaxies (SPT-SMGs) are strong gravitationally lensed which allows us to observe the dust and gas content in them at high resolution, e.g. with the Atacama Large Millimeter/submillimeter Array (ALMA). Star formation rate (SFR) is an important property to study cosmic evolution. In dust obscured galaxies, infrared luminosity (LIR) is used as a tracer of SFR. However, it is observationally expensive to sample the peak of the dust SED and get resolved LIR. In our analysis, we develop resolved p-H2O(2 0,2 − 1 1,1) (νrest = 987.927 GHz), a bright emission line, as a tracer of SFR. From three SPT-SMGs and an active galactic nuclei (AGN) at z ~ 3, we find that H2O is correlated with LFIR at both the global galaxy scale and also at resolved kiloparsec scales. Moreover, the presence of an AGN does not affect this correlation which shows that p-H2O(2 0,2 − 1 1,1) is excited by FIR photon pumping. Our future work constrains the dust SED peak in these galaxies which allows us to probe the spatial correlations of dust temperature, dust mass, infrared luminosity, water and CO. The theoretical understanding of the DSFG population has been challenging, especially during the Epoch of Reionization (EoR), between z∼15−6. Using multiple CO transitions, CO(3 − 2), CO(6 − 5), CO(7 − 6), and CO(10 − 9), p-H2O(2 1,1 − 2 0,2 ), and [CI](2 − 1), we constrain the physical properties of SPT0311-58, a pair of galaxies (West and East) in the Epoch or Reionization (EoR) at z = 6.9. The H2O detection in West is the most distant detection in a star forming galaxy in the literature. We performed visibility based parametric lensing reconstruction and non-LTE Large Velocity Gradient (LVG) radiative transfer modeling to estimate the physical properties. The CO spectral line energy distribution in West and East, the CO-to-H2 conversion factor (αCO), and the gas depletion time scales are consistent with the high-redshift DSFGs in the literature within the uncertainties.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Astronomy

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Jarugula, Sreevani

Contributors dc:contributor

• Vieira, Joaquin
• Holder, Gilbert
• Wong, Tony
• Liu, Xin

• High-redshift Galaxies
• Starburst Galaxies
• Ism

Statement dc:rights

• Copyright 2022 Sreevani Jarugula

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/117744

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F117744