A physical model for z∼ 2 dust-obscured galaxies

By D. Narayanan, A. Dey, C. Hayward, Thomas J. Cox, R. Bussmann, M. Brodwin, P. Jonsson, P. Hopkins, B. Groves, J. Younger and 1 more. 2009

146 citations recorded by the source corpus.

We present a physical model for the origin of z ∼ 2 dust-obscured galaxies (DOGs), a class of high-redshift ultraluminous infrared galaxies (ULIRGs) selected at 24 μm which are particularly optically faint (F24 μm/FR > 1000). By combining N-body/smoothed particle hydrodynamic simulations of high-redshift galaxy evolution with 3D polychromatic dust radiative transfer models, we find that luminous DOGs (with F24 0.3 mJy at z ∼ 2) are well modelled as extreme gas-rich mergers in massive (∼5 × 10 12 -10 13 M� ) haloes, with elevated star formation rates (SFR; ∼500-1000 Myr −1 ) and/or significant active galactic nuclei (AGN) growth ( u MBH 0. 5Myr −1 ), whereas less luminous DOGs are more diverse in nature. At final coalescence, merger-driven DOGs transition from being starburst dominated to AGN dominated, evolving from a 'bump' to a power-law (PL) shaped mid-IR (Infrared Array Camera, IRAC) spectral energy distribution (SED). After the DOG phase, the galaxy settles back to exhibiting a 'bump' SED with bluer colours and lower SFRs. While canonically PL galaxies are associated with being AGN dominated, we find that the PL mid-IR SED can owe both to direct AGN contribution and to a heavily dust obscured stellar bump at times that the galaxy is starburst dominated. Thus, PL galaxies can be either starburst or AGN dominated. Less luminous DOGs can be well-represented either by mergers or by massive (Mbaryon ≈ 5 × 10 11 M� ) secularly evolving gas-rich disc galaxies (with SFR 50 Myr −1 ). By utilizing similar models as those employed in the submillimetre galaxy (SMG) formation study of Narayanan et al., we investigate the connection between DOGs and SMGs. We find that the most heavily star-forming merger-driven DOGs can be selected as submillimetre galaxies, while both merger-driven and secularly evolving DOGs typically satisfy the BzK selection criteria. The model SEDs from the simulated galaxies match observed data reasonably well, though Mrk 231 and Arp 220 templates provide worse matches. Our models provide testable predictions of the physical masses, dust temperatures, CO linewidths and location on the MBH-Mbulge relation of DOGs. Finally, we provide public SED templates derived from these

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

A general model for the CO–H2 conversion factor in galaxies with applications to the star formation law (2011, methodology): “While the mean gas surface densities in e.g. z ∼ 2 SMGs are larger than low-redshift mergers (e.g. Tacconi et al. 2008; Narayanan et al. 2010a), both the dust temperatures and gas velocity dispersions also rise commensurately.”
MOST SUBMILLIMETER GALAXIES ARE MAJOR MERGERS (2010, background): “1 of Narayanan et al. (2010a) show the evolution of the star formation rate, bolometric luminosity, and S850µm during simulated gas-rich major mergers.”
THE ERA OF STAR FORMATION IN GALAXY CLUSTERS (2013, background): “If these observed starbursts are merger-induced, recent simulations (e.g., Springel et al. 2005; Hopkins et al. 2006; Narayanan et al. 2010) predict that AGN feedback may also play a significant role in quenching the star formation in these cluster galaxies.”
Revisiting the Unified Model of Active Galactic Nuclei (2015, background): “Major mergers of gas rich systems in the early universe have been suggested to result in powerful dusty SF systems (dust-obscured galaxies, DOGs) surrounding a buried AGN whose power is increasing with time (see Narayanan et al. 2010, and references therein).”
The stellar masses and specific star-formation rates of submillimetre galaxies (2011, methodology): “This argument is supported by hydrodynamical simulations of SMGs (Narayanan et al. 2009, 2010b; Hayward et al. 2011a,b), where only ≃ 30% of the stellar mass is distributed over the inner radius of 2.5 kpc, roughly the size over which Engel et al. (2010) calculated dynamical masses.”
Dusty Star Forming Galaxies at High Redshift (2014, methodology): “Narayanan et al. (2010c) examined the properties of a series of galaxy mergers over a range of galaxy masses andmerger mass ratios, as well as idealized isolated disk galaxies utilizing gadget as the N-body/hydrodynamics solver.”
WHAT DOES A SUBMILLIMETER GALAXY SELECTION ACTUALLY SELECT? THE DEPENDENCE OF SUBMILLIMETER FLUX DENSITY ON STAR FORMATION RATE AND DUST MASS (2010, methodology): “…et al. 2010); local ULIRGs (Younger et al. 2009a); massive, quiescent, compact z ∼ 2 galaxies (Wuyts et al. 2009, 2010); 24 μm selected galaxies (Narayanan et al. 2010b); K+A/post-starburst galaxies (Snyder et al. 2011); and extended ultraviolet (XUV) disks (Bush et al. 2010), among other…”
The CO-H2 Conversion Factor in Disc Galaxies and Mergers (2011, methodology): “This value is motivated in part by simulations by Jonsson et al. (2010) which showed covering fractions comparable to these result in synthetic SEDs of disc galaxies comparable to the SINGS sample (Kennicutt et al. 2003).”
Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution, and implications for the IMF (2012, background): “(1) the AGN typically do not dominate (but can still contribute significantly to) the luminosity of our model SMGs because the SEDs during the phase of strong AGN activity tend to be hotter than during the starburst phase (e.g. Younger et al. 2009, Snyder et al. 2012), so the mergers are typically n”
ON SIZES, KINEMATICS, M/L GRADIENTS, AND LIGHT PROFILES OF MASSIVE COMPACT GALAXIES AT z ∼ 2 (2010, background): “Narayanan et al. (2010) describe how during a relatively short (< 50 Myr) period at final coalescence (orange) a peak in emission at sub-millimeter wavelengths is reached.”