WHAT DOES A SUBMILLIMETER GALAXY SELECTION ACTUALLY SELECT? THE DEPENDENCE OF SUBMILLIMETER FLUX DENSITY ON STAR FORMATION RATE AND DUST MASS

By C. Hayward, D. Keres̆, P. Jonsson, D. Narayanan, Thomas J. Cox, L. Hernquist. 2010

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We perform three-dimensional dust radiative transfer (RT) calculations on hydrodynamic simulations of isolated and merging disk galaxies in order to quantitatively study the dependence of observed-frame submillimeter (submm) flux density on galaxy properties. We find that submm flux density and star formation rate (SFR) are related in dramatically different ways for quiescently star-forming galaxies and starbursts. Because the stars formed in the merger-induced starburst do not dominate the bolometric luminosity and the rapid drop in dust mass and more compact geometry cause a sharp increase in dust temperature during the burst, starbursts are very inefficient at boosting submm flux density (e.g., a ≳ 16 × boost in SFR yields a ≲ 2 × boost in submm flux density). Moreover, the ratio of submm flux density to SFR differs significantly between the two modes; thus one cannot assume that the galaxies with highest submm flux density are necessarily those with the highest bolometric luminosity or SFR. These results have important consequences for the bright submillimeter-selected galaxy (SMG) population. Among them are: (1) The SMG population is heterogeneous. In addition to merger-driven starbursts, there is a subpopulation of galaxy pairs, where two disks undergoing a major merger but not yet strongly interacting are blended into one submm source because of the large (≳ 15” or ∼130 kpc at z = 2) beam of single-dish submm telescopes. (2) SMGs must be very massive (M⋆ ≳ 6 × 1010 M☉). (3) The infall phase makes the SMG duty cycle a factor of a few greater than what is expected for a merger-driven starburst. Finally, we provide fitting functions for SCUBA and AzTEC submm flux densities as a function of SFR and dust mass and bolometric luminosity and dust mass; these should be useful for calculating submm flux density in semi-analytic models and cosmological simulations when performing full RT is computationally not feasible.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/6fa24d631d91718e8a4a50df188e5ce942c324e2

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Citations in the corpus

Dusty Star Forming Galaxies at High Redshift (2014, background): “…be consistent with theories that suggest that SMGsmay be made up of both merger-induced starbursts caught at final coalescence (that may have more extreme ISM conditions), as well as individual disk galaxies at high-z that may have a lower-excitation ISM (e.g. Hayward et al., 2011, 2012, 2013b).”
A deep ALMA image of the Hubble Ultra Deep Field (2016, background): “…an interesting and important challenge to theoretical models of galaxy formation (e.g. Baugh et al. 2005; Khochfar & Silk 2009; Davé et al. 2010; Hayward et al. 2011; Narayanan et al. 2015), but they provide only ' 10− 15% of the known far-infrared/mm background (Fixsen et al. 1998; Scott et…”
An ALMA survey of the SCUBA-2 CLS UDS field: physical properties of 707 sub-millimetre galaxies (2019, background): “…from https://academ ic.oup.com /m nras/article/494/3/3828/5815090 by Jacob H eeren user on 11 January 2021 galaxies could represent a heterogeneous mix of these two classes of systems, encompassing both physical processes (e.g. Hayward et al. 2011; Narayanan et al. 2015; McAlpine et al. 2019).”
Star formation in galaxy mergers with realistic models of stellar feedback and the interstellar medium (2012, background): “Reproducing their abundance and luminosities remains a challenge for current models of galaxy formation (Baugh et al. 2005; Swinbank et al. 2008; Younger et al. 2009a; Hayward et al. 2010, 2011; Narayanan et al. 2010).”
An ALMA survey of sub-millimetre Galaxies in the Extended Chandra Deep Field South: the far-infrared properties of SMGs (2013, methodology): “In contrast, numerical models of Hayward et al. (2011) (see also Narayanan et al. 2009 and Davé et al. 2010) suggest that SMGs are dominated by secular bursts in gas-rich disk galaxies, with “standard” IMFs.”
EVIDENCE FOR A CLUMPY, ROTATING GAS DISK IN A SUBMILLIMETER GALAXY AT z = 4 (2012, background): “Many SMGs are believed to be starburst–dominated major mergers (e.g., Chapman et al. 2003b; Engel et al. 2010; Narayanan et al. 2010; Hayward et al. 2011, 2012).”
A general model for the CO–H2 conversion factor in galaxies with applications to the star formation law (2011, methodology): “Model z3b5e undergoes a luminous burst of ∼1500 M yr−1, and may be selected as a SMG when it merges (Narayanan et al. 2009; Hayward et al. 2011).”
The star formation main sequence and stellar mass assembly of galaxies in the Illustris simulation (2014, methodology): “However, in higher-resolution idealised merger simulations that employed the same ISM model, SFR elevations of an order of magnitude or more have been found (e.g. Cox et al. 2008; Hayward et al. 2011, 2014; Torrey et al. 2012).”
The stellar masses and specific star-formation rates of submillimetre galaxies (2011, methodology): “…their massive dust-enshrouded star-formation rates are fuelled primarily by mergers, or by cold gas infall (Swinbank et al. 2008; Davé et al. 2010; González et al. 2011; Narayanan et al. ⋆ Scottish Universities Physics Alliance 2010b; Ricciardelli et al. 2010; Hayward et al. 2011a,b, 2012).”
Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations (2012, methodology): “It is also supported by simulations such as those presented by Hayward et al. (2011), which are based on the observational evidences provided by Alexander et al. (2008) and show that accretion/SF histories in SMGs are not strictly synchronized.”
KILOPARSEC-SCALE DUST DISKS IN HIGH-REDSHIFT LUMINOUS SUBMILLIMETER GALAXIES (2016, background): “…et al. 2010), although non-cosmological hydrodynamic simulations have suggested that SMGs could be a heterogeneous population: a mix of pre-merger pairs of disk galaxies, merger–induced starbursts, and isolated gas–rich disk galaxies undergoing a secular burst (e.g., Hayward et al. 2011, 2012).”
AN ALMA SURVEY OF SUBMILLIMETER GALAXIES IN THE EXTENDED CHANDRA DEEP FIELD SOUTH: SOURCE CATALOG AND MULTIPLICITY (2013, background): “The predominant theory for SMG formation is that the majority of such sources are starbursting major mergers (e.g., Chapman et al. 2003; Engel et al. 2010; Narayanan et al. 2010; Hayward et al. 2011, 2012).”
A Herschel view of the far-infrared properties of submillimetre galaxies (2012, methodology): “To quantitatively confirm this agreement we compare our dust temperatures with those of the hydrodynamic simulations of Hayward et al. (2011).”
Three-Dimensional Dust Radiative Transfer ∗ (2013, background): “…Gordon 1996), molecular clouds (Pelkonen, Juvela & Padoan 2009, Steinacker et al. 2005), spiral galaxies (Bianchi 2008, Schechtman-Rook, Bershady & Wood 2012), interacting and starburst galaxies (Chakrabarti et al. 2007, Hayward et al. 2011), and AGN (Schartmann et al. 2008, Stalevski et al. 2012).”
Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution, and implications for the IMF (2012, background): “A more top-heavy IMF results in both more luminosity emitted and more dust produced per unit SFR; consequently, the submm flux per unit SFR is increased significantly (see B05 and Hayward et al. 2011a, hereafter H11, for details).”
SUBMILLIMETER GALAXIES AS PROGENITORS OF COMPACT QUIESCENT GALAXIES (2014, background): “In the simulations of Hayward et al. (2011) the gas fraction decrease from 45% to 40% in isolated disks and from 17.5% to 15% in merging galaxies, from the peak of the starburst to when it ends, corresponding to a decrease in gas mass of 5% and 15% during this time.”