EXPLAINING THE [C ii]157.7 μm DEFICIT IN LUMINOUS INFRARED GALAXIES—FIRST RESULTS FROM A HERSCHEL/PACS STUDY OF THE GOALS SAMPLE

By T. Díaz-Santos, Lee Armus, Vassilis Charmandaris, S. Stierwalt, E. Murphy, S. Haan, H. Inami, S. Malhotra, R. Meijerink, G. Stacey and 42 more. 2013

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We present the first results of a survey of the [C ii]157.7 μm emission line in 241 luminous infrared galaxies (LIRGs) comprising the Great Observatories All-sky LIRG Survey (GOALS) sample, obtained with the PACS instrument on board the Herschel Space Observatory. The [C ii] luminosities, L[C ii], of the LIRGs in GOALS range from ∼107 to 2 × 109 L☉. We find that LIRGs show a tight correlation of [C ii]/FIR with far-IR (FIR) flux density ratios, with a strong negative trend spanning from ∼10−2 to 10−4, as the average temperature of dust increases. We find correlations between the [C ii]/FIR ratio and the strength of the 9.7 μm silicate absorption feature as well as with the luminosity surface density of the mid-IR emitting region (ΣMIR), suggesting that warmer, more compact starbursts have substantially smaller [C ii]/FIR ratios. Pure star-forming LIRGs have a mean [C ii]/FIR ∼ 4 × 10−3, while galaxies with low polycyclic aromatic hydrocarbon (PAH) equivalent widths (EWs), indicative of the presence of active galactic nuclei (AGNs), span the full range in [C ii]/FIR. However, we show that even when only pure star-forming galaxies are considered, the [C ii]/FIR ratio still drops by an order of magnitude, from 10−2 to 10−3, with ΣMIR and ΣIR, implying that the [C ii]157.7 μm luminosity is not a good indicator of the star formation rate (SFR) for most local LIRGs, for it does not scale linearly with the warm dust emission most likely associated to the youngest stars. Moreover, even in LIRGs in which we detect an AGN in the mid-IR, the majority (2/3) of galaxies show [C ii]/FIR ⩾ 10−3 typical of high 6.2 μm PAH EW sources, suggesting that most AGNs do not contribute significantly to the FIR emission. We provide an empirical relation between the [C ii]/FIR and the specific SFR for star-forming LIRGs. Finally, we present predictions for the starburst size based on the observed [C ii] and FIR luminosities which should be useful for comparing with results from future surveys of high-redshift galaxies with ALMA and CCAT.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/db24fc5592e18a74150564a0b529d7308f83c602

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Citations in the corpus

ALMA IMAGING OF GAS AND DUST IN A GALAXY PROTOCLUSTER AT REDSHIFT 5.3: [C ii] EMISSION IN “TYPICAL” GALAXIES AND DUSTY STARBURSTS ≈1 BILLION YEARS AFTER THE BIG BANG (2014, background): “This is consistent with normal, star-forming galaxies at low redshift, but significantly higher than in dusty quasars and extreme starburst galaxies (e.g., Gracia-Carpio et al. 2011; Diaz-Santos et al. 2013).”
AN INTENSELY STAR-FORMING GALAXY AT z ∼ 7 WITH LOW DUST AND METAL CONTENT REVEALED BY DEEP ALMA AND HST OBSERVATIONS (2013, background): “Because galaxies with fainter FIR/mid-IR luminosities have a larger ratio of L[CII]/LFIR in the datasets probed by Graciá-Carpio et al. (2011) and Diaz-Santos et al. (2013), more dust-free star-formation is expected in such systems.”
An ALMA [C ii] Survey of 27 Quasars at z > 5.94 (2018, background): “…and drops by an order of magnitude toward the bright end (the so-called “[C II] deficit”), in particular in the presence of high-temperature, compact dust emission (Malhotra et al. 2001; Díaz-Santos et al. 2013, 2014, 2017; Farrah et al. 2013; Sargsyan et al. 2014; Herrera-Camus et al. 2015).”
Dusty Star Forming Galaxies at High Redshift (2014, result): “Hence, one reasonable approach for future studies may involve comparing the [CII]/FIR ratio against luminosity surface density, as in Díaz-Santos et al. (2013).”
The applicability of far-infrared fine-structure lines as star formation rate tracers over wide ranges of metallicities and galaxy types (2014, methodology): “; (3) Sargsyan et al. (2012); (4) Díaz-Santos et al. (2013); (5) Farrah et al. (2013).”
The Herschel Dwarf Galaxy Survey - I. Properties of the low-metallicity ISM from PACS spectroscopy (2015, background): “A deficit in the FIR line intensities is, however, found in luminous IR galaxies (e.g., Luhman et al. 2003; Graciá-Carpio et al. 2011; Croxall et al. 2012; Díaz-Santos et al. 2013).”
The Herschel view of the dominant mode of galaxy growth from z = 4 to the present day (2014, background): “…aromatic hydrocarbon (PAH) emission lines equivalent widths (Pope et al. 2008; Fadda et al. 2010; Elbaz et al. 2011; Nordon et al. 2012), [C ii] to far-infrared (FIR) luminosity (LFIR) ratios (Díaz-Santos et al. 2013), and universal FIR spectral energy distributions (SEDs; Elbaz et al. 2011).”
Very extended cold gas, star formation and outflows in the halo of a bright QSO at z>6 (2014, background): “…released by dust grains and so the relative efficiency of cooling via [C ii] emission with respect to dust cooling (Luhman et al. 2003; Díaz-Santos et al. 2013); (iii) a high ionisation parameter U (which is essentially linked to (ii)) that reduces the opacity of hydrogen atoms…”