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Published December 1, 2014 | Published + Submitted
Journal Article Open

Early Science with the Large Millimeter Telescope: Exploring the Effect of AGN Activity on the Relationships between Molecular Gas, Dust, and Star Formation

Abstract

The molecular gas, H_2, that fuels star formation in galaxies is difficult to observe directly. As such, the ratio of L_IR to L'_CO is an observational estimate of the star formation rate compared with the amount of molecular gas available to form stars, which is related to the star formation efficiency and the inverse of the gas consumption timescale. We test what effect an IR luminous active galactic nucleus (AGN) has on the ratio L_IR/L'_CO in a sample of 24 intermediate redshift galaxies from the 5 mJy Unbiased Spitzer Extragalactic Survey (5MUSES). We obtain new CO(1–0) observations with the Redshift Search Receiver on the Large Millimeter Telescope. We diagnose the presence and strength of an AGN using Spitzer IRS spectroscopy. We find that removing the AGN contribution to L^(tot)_IR results in a mean L^(SF)_IR/L'_CO for our entire sample consistent with the mean L_IR/L'_CO derived for a large sample of star forming galaxies from z ∼ 0–3.We also include in our comparison the relative amount of polycyclic aromatic hydrocarbon emission for our sample and a literature sample of local and high-redshift ultra luminous infrared galaxies and find a consistent trend between L_6.2/L^(SF)_IR and L^(SF)_IR/L'CO, such that small dust grain emission decreases with increasing L^(SF)_IR/L'_CO for both local and high-redshift dusty galaxies.

Additional Information

© 2014 American Astronomical Society. Received 12 July 2014; accepted for publication 14 October 2014; published 14 November 2014. We thank the anonymous referee for the helpful comments which have improved the clarity of this work. This work would not have been possible without the long-term financial support from the Mexican Science and Technology Funding Agency, CONACYT (Consejo Nacional de Ciencia y Tecnología) during the construction and early operational phase of the Large Millimeter Telescope Alfonso Serrano, as well as support from the US National Science Foundation via the University Radio Observatory program, the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) and the University of Massachusetts (UMASS). The UMass LMT group acknowledges support from NSF URO and ATI grants (AST-0096854 and AST-0704966) for the LMT project and the construction of the RSR. A.K. would like to acknowledge support from a William Bannick Student Travel Grant. We are grateful to all the LMT observers from Mexico and UMass who took data for this project. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA, and the Herschel Space Observatory, a European Space Agency Cornerstone Mission with significant participation by NASA. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Attached Files

Published - 0004-637X_796_2_135.pdf

Submitted - 1411.1065v1.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 19, 2023