Mid-Infrared Spectral Diagnosis of Submillimeter Galaxies

By Adrian Pope, R. Chary, D. M. Alexander, Lee Armus, Mark Dickinson, D. Elbaz, D. Frayer, D. Scott, H. Teplitz. 2007

320 citations recorded by the source corpus.

We present deep mid-IR spectroscopy with Spitzer of 13 SMGs in the GOODS-N field. We find strong PAH emission in all of our targets, which allows us to measure mid-IR spectroscopic redshifts and place constraints on the contribution from star formation and AGN activity to the mid-IR emission. In the high-S/N composite spectrum, we find that the hot dust continuum from an AGN contributes at most 30% of the mid-IR luminosity. Individually, only 2/13 SMGs have continuum emission dominating the mid-IR luminosity; one of these SMGs, C1, remains undetected in the deep X-ray images but shows a steeply rising continuum in the mid-IR indicative of a Compton-thick AGN. We find that the mid-IR properties of SMGs are distinct from those of 24 μm-selected ULIRGs at z ∼ 2; the former are predominantly dominated by star formation, while the latter are a more heterogeneous sample with many showing significant AGN activity. We fit the IRS spectrum and the mid-IR to radio photometry of SMGs with template SEDs to determine the best estimate of the total IR luminosity from star formation. While many SMGs contain an AGN as evinced by their X-ray properties, our multiwavelength analysis shows that the total IR luminosity, LIR, in SMGs is dominated by star formation. We find that high-redshift SMGs lie on the relation between LIR and LPAH ,6.2 (or LPAH ,7.7 or LPAH ,11.3) that has been established for local starburst galaxies. This suggests that PAH luminosity can be used as a proxy for the SFR in SMGs. SMGs are consistent with being a short-lived cool phase in a massive merger where the AGN does not appear to have become strong enough to heat the dust and dominate the mid- or far-IR emission.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/35b4698ce4ad67861db74fdb0f4d6906f8721477

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. D. M. Alexander
4. R. Dav'e
5. R. Somerville
6. D. Narayanan
7. Thomas J. Cox
8. A. Dekel

Citations in the corpus

• THE ERA OF STAR FORMATION IN GALAXY CLUSTERS (2013, result): “This model also corroborates the findings of Brodwin et al. (2008) that the brightest Dust-Obscured Galaxies (DOGS, Dey et al. 2008; Pope et al. 2008), which are dusty AGN-dominated ULIRGs at 1.5 . z .”
• A NEW DIAGNOSTIC OF ACTIVE GALACTIC NUCLEI: REVEALING HIGHLY ABSORBED SYSTEMS AT REDSHIFT >0.3 (2011, background): “Midinfrared aromatic features can also be used to diagnose the powering source in galaxies (Genzel et al. 1998; Lutz et al. 1998; Pope et al. 2008).”
• EXPLAINING THE [C ii]157.7 μm DEFICIT IN LUMINOUS INFRARED GALAXIES—FIRST RESULTS FROM A HERSCHEL/PACS STUDY OF THE GOALS SAMPLE (2013, background): “…widely used for the detection of AGN activity in galaxies at low and high redshifts (Genzel et al. 1998; Armus et al. 2007; Desai et al. 2007; Spoon et al. 2007; Pope et al. 2008; Murphy et al. 2009; MenéndezDelmestre et al. 2009; Veilleux et al. 2009; Petric et al. 2011; Stierwalt et al. 2013a).”
• Dusty Star Forming Galaxies at High Redshift (2014, background): “5 illustrates a characteristic SED of a z = 2LIR = 3 × 1012L⊙ galaxy (Pope et al., 2008b) in relation to some well known local ULIRGs (Arp220, Mrk231, templates provided by Polletta et al., 2007).”
• What drives the growth of black holes (2011, background): “…of these objects also host AGN (e.g., Alexander et al., 2003a, 2005; Laird et al., 2010), but they generally have Spitzer IRS mid-IR spectra that are dominated by star formation as indicated by luminous PAH emission features (e.g., Valiante et al., 2007; Pope et al., 2008; Coppin et al., 2010).”
• GOODS–Herschel: an infrared main sequence for star-forming galaxies (2011, methodology): “; technique similar to that from Ivison et al. 2004 and Pope et al. 2008b for sub-mm galaxies): Sν[4.5µm] > Sν[3.6µm] log10 ( Sν [24µm] Sν[8 µm] ) < 3.64× log10 ( Sν[8 µm] Sν[4.5µm] ) + 0.15 (16) X-ray/optical AGN that also meet the infrared power-law criteria are counted as power-law sources in…”
• The LABOCA survey of the Extended Chandra Deep Field-South: clustering of submillimetre galaxies (2011, background): “…believed to arise from intense, but highly obscured, gas-rich starbursts (e.g. Alexander et al. 2005; Greve et al. 2005; Tacconi et al. 2006, 2008; Pope et al. 2008; Ivison et al. 2011), suggesting that they may represent the formation phase of the most massive local galaxies: giant ellipticals…”
• The LABOCA survey of the Extended Chandra Deep Field South: A photometric redshift survey of submillimetre galaxies (2010, background): “Studies of mid-IR spectra of SMGs have shown that they are similar to M82 with an additional power-law contribution, potentially due to AGN emission or hot dust (Menéndez-Delmestre et al. 2007, 2009; Pope et al. 2008; Coppin et al. 2010b).”
• A physical model for z∼ 2 dust-obscured galaxies (2009, methodology): “In order to compare with Pope et al. (2008b)’s analysis of GOODS-N DOGs (selected with F24 > 100 μJy) in BzK space, we include all DOGs with F24 > 100 μJy at z = 2.”
• A CORRELATION BETWEEN STAR FORMATION RATE AND AVERAGE BLACK HOLE ACCRETION IN STAR-FORMING GALAXIES (2013, background): “Detailed spectral template fitting is required to disentangle AGN and star forming activities in optical or mid-IR observations (e.g. Kauffmann et al. 2003; Pope et al. 2008).”
• A Herschel/PACS Far-infrared Line Emission Survey of Local Luminous Infrared Galaxies (2017, background): “…Magnelli et al. 2011), and a number of works have already shown that local LIRGs (and not ULIRGs) are probably the closest local analogs of this high-z, IR-bright galaxy population (Desai et al. 2007; Pope et al. 2008; Menéndez-Delmestre et al. 2009; Dı́az-Santos et al. 2010b; Stacey et al. 2010).”
• The stellar masses and specific star-formation rates of submillimetre galaxies (2011, background): “%) contamination of their bolometric luminosities by active galactic nuclei (AGNs; Alexander et al. 2005, 2008; Menéndez-Delmestre et al. 2007, 2009; Valiante et al. 2007; Pope et al. 2008; Hainline et al. 2009; Murphy et al. 2009; Watabe et al. 2009, M10).”
• COLOR–MAGNITUDE RELATIONS OF ACTIVE AND NON-ACTIVE GALAXIES IN THE CHANDRA DEEP FIELDS: HIGH-REDSHIFT CONSTRAINTS AND STELLAR-MASS SELECTION EFFECTS (2010, background): “…strongly star-forming, dust-obscured galaxies atz≈ 1–3 that have been studied extensively (e.g., Alexander et al. 2005a, 2005b; Chapman et al. 2005; Pope et al. 2006, 2008; Biggs et al. 2010; Laird et al. 2010; Swinbank et al. 2010; Wardlow et al. 2010) but have yet to be put into the context of…”
• MOST SUBMILLIMETER GALAXIES ARE MAJOR MERGERS (2010, background): “Veilleux et al. (2009) find local ULIRG luminosities to have ≈ 39% AGN contribution; estimates for SMGs are more uncertain, but span a range of 8 - 35% (Swinbank et al. 2004; Alexander et al. 2005, 2008a; Lutz et al. 2005; Valiante et al. 2007; Pope et al. 2008; Menéndez-Delmestre et al. 2009).”
• A survey of molecular gas in luminous sub-millimetre galaxies (2012, methodology): “As a result the final target sample includes SMGs selected to have precise spectroscopic redshifts, derived using one or more of the following techniques: (i) Lyman α emission (C05); (ii) Hα emission (Swinbank et al. 2004) and (iii) polycyclic aromatic hydrocarbon emission from mid-IR spectroscopy w”
• VERY HIGH GAS FRACTIONS AND EXTENDED GAS RESERVOIRS IN z = 1.5 DISK GALAXIES (2009, methodology): “…not to adopt the IR luminosities for SMGs estimated by Greve et al. (2005) but use a lower conversion factor between 850µm flux and IR luminosity to account for the evidence that their SEDs are colder than previously thought (e.g., Pope et al. 2006; 2008; Kovacs et al. 2006; Daddi et al. 2009).”
• Far-infrared spectral energy distribution fitting for galaxies near and far (2012, background): “The mid-infrared spectra of dusty starbursts have been shown to vary substantially at both low-z and high-z (Brandl et al. 2006; Pope et al. 2008; Menéndez-Delmestre et al. 2009).”
• A Significant Population of Very Luminous Dust-Obscured Galaxies at Redshift z ~ 2 (2008, background): “…above, the DOGs are expected to have warmer dust temperatures than the SMGs, and it is indeed interesting that the detection rate of SMGs at MIPS wavelengths (24µm and 70µm) is low, with only <∼ 40% of the SMGs in the GOODS-N field having 24µm flux densities F24µm ≥ 0.3mJy (Pope et al. 2008).”