In this article, the authors present the first results of a survey of the [C II]157.7 {$μ$}m 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.
Abstract:
We present the first results of a survey of the [C II]157.7 {$μ$}m 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 ~{}10$^{7}$ to 2 { imes} 10$^{9}$ 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 {$μ$}m silicate absorption feature as well as with the luminosity surface density of the mid-IR emitting region ({$Sigma$}$_{MIR}$), suggesting that warmer, more compact starbursts have substantially smaller [C II]/FIR ratios. Pure star-forming LIRGs have a mean [C II]/FIR ~{} 4 { imes} 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 {$Sigma$}$_{MIR}$ and {$Sigma$}$_{IR}$, implying that the [C II]157.7 {$μ$}m 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 {gt}= 10$^{-3}$ typical of high 6.2 {$μ$}m 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.
TL;DR: In this paper, the first results of a high-resolution Karl G. Jansky Very Large Array imaging survey of luminous and ultra-luminous infrared galaxies (U/LIRGs) in the Great Observatories All-sky LIRG Survey were presented.
TL;DR: In this paper, the authors present observations and analysis of an unusual [C II] emission line in the very luminous QSO SDSS J155426.16+193703.0 at z~4.6.
TL;DR: In this article, an analysis of far-infrared (FIR) [CII] and [OI] fine structure line and continuum observations obtained with Herschel/PACS, and with the IRAM Plateau de Bure Interferometer, of Lyman-break analogs (LBAs) at z ~ 0.2.
TL;DR: In this paper, a morphological classification of 89 luminous infrared galaxies (LIRGs) from the GOALS data was performed using non-parametric coefficients and compared their morphology as a function of wavelength.
TL;DR: The detection of the far-infrared (FIR) fine-structure line of singly ionised nitrogen, Nplusa, within the peak epoch of galaxy assembly, from a strongly lensed galaxy, hereafter ''The Red Radio Ring'' the RRR, at z = 2.55 was reported in this paper.
TL;DR: In this paper, the Schmidt law was used to model the global star formation law over the full range of gas densities and star formation rates observed in galaxies, and the results showed that the SFR scales with the ratio of the gas density to the average orbital timescale.
TL;DR: In this paper, the Schmidt law was used to model the global star formation law, over the full range of gas densities and star formation rates (SFRs) observed in galaxies.
TL;DR: Herschel was launched on 14 May 2009, and is now an operational ESA space observatory o ering unprecedented observational capabilities in the far-infrared and sub-millimetre spectral range 55 671 m.
TL;DR: At the highest luminosities (Lir > 1012 ), nearly all objects appear to be advanced mergers powered by a mixture of circumnuclear starburst and active galactic nucleus energy sources, both of which are fueled by an enormous concentration of molecular gas that has been funneled into the merger nucleus as discussed by the authors.
TL;DR: The Photodetector Array Camera and Spectrometer (PACS) as discussed by the authors is one of the three science instruments on ESA's far infrared and sub-mil- limetre observatory.
The authors present the first results of a survey of the [ C ii ] 157. The authors 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. However, the authors 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. Moreover, even in LIRGs in which the authors 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. The authors provide an empirical relation between the [ C ii ] /FIR and the specific SFR for star-forming LIRGs. Finally, the authors 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. 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.
Q2. What is the important source of photo-electrons?
In particular, polycyclic aromatic hydrocarbons (PAHs) are thought to be an important source of photo-electrons (Helou et al. 2001) that contribute, through kinetic energy transfer, to the heating of the neutral gas which subsequently cools down via collision with C+ atoms and other elements in photo-dissociation regions (PDRs; Tielens & Hollenbach 1985; Wolfire et al. 1995).
Q3. What is the net effect of the emission of dust particles?
The net effect is the decreasing of the efficiency in the transformation of incident UV radiation into gas heating without an accompanied reduction of the dust emission (Wolfire et al.
Q4. What is the trend for LIRGs with deeper silicate strengths?
There is a clear trend for LIRGs with deeper 9.7 μm silicate strengths (S9.7 μm), higher mid-IR luminosity surface densities (ΣMIR), smaller fractions of extended emission (FEE13.2 μm) and higher SSFRs to display lower [C ii]/FIR ratios.
Q5. How many spectral elements are in each pixel?
The number of spectral elements in each pixel is 16, which are rearranged together via an image slicer over two 16 × 25 Ge:Ga detector arrays (blue and red cameras).
Q6. What is the FIR ratio for the GOALS sample?
Figure 2 (upper panel) shows the [C ii]157.7 μm/FIR ratio for the GOALS sample as a function of the FIR PACS Sν 63 μm/ Sν 158 μm continuum flux density ratio.
Q7. Why is the [C ii] line less efficient?
It has also been suggested that in sources where G0/nH is high ( 102 cm3) the [C ii] line is a less efficient coolant of the ISM because of the following reason.