scholarly journals The molecular gas in Luminous Infrared Galaxies: a new emergent picture

2012 ◽  
Vol 8 (S292) ◽  
pp. 209-214
Author(s):  
Padelis P. Papadopoulos ◽  
Zhi-Yu Zhang ◽  
Axel Weiss ◽  
Paul van der Werf ◽  
Kate Isaak ◽  
...  
Keyword(s):  
Cosmic Ray ◽  
Molecular Gas ◽  
Infrared Galaxies ◽  
Space Observatory ◽  
Local Universe ◽  
Star Forming ◽  
Luminous Infrared Galaxies ◽  
Physical Conditions ◽  
J 13 ◽  
Line Survey

AbstractResults from a large, multi-J CO, 13CO, and HCN line survey of Luminous Infrared Galaxies (LIRGs: LIR≥ 1010 L⊙) in the local Universe (z≤0.1), complemented by CO J=4–3 up to J=13–12 observations from the Herschel Space Observatory (HSO), paints a new picture for the average conditions of the molecular gas of the most luminous of these galaxies with turbulence and/or large cosmic ray (CR) energy densities UCR rather than far-UV/optical photons from star-forming sites as the dominant heating sources. Especially in ULIRGs (LIR>1012 L⊙) the Photon Dominated Regions (PDRs) can encompass at most a few % of their molecular gas mass while the large UCR∼ 103 UCR, Galaxy, and the strong turbulence in these merger/starbursts, can volumetrically heat much of their molecular gas to Tkin∼ (100-200) K, unhindered by the high dust extinctions. Moreover the strong supersonic turbulence in ULIRGs relocates much of their molecular gas at much higher average densities (≥104 cm−3) than in isolated spirals (∼ 102–103 cm−3). This renders low-J CO lines incapable of constraining the properties of the bulk of the molecular gas in ULIRGs, with substantial and systematic underestimates of its mass possible when only such lines are used. Finally a comparative study of multi-J HCN lines and CO SLEDs from J=1–0 up to J=13–12 of NGC 6240 and Arp 193 offers a clear example of two merger/starbursts whose similar low-J CO SLEDs, and LIR/LCO,1−0 and LHCN, 1−0/LCO,1-0 ratios (proxies of the so-called SF efficiency and dense gas mass fraction), yield no indications about their strongly diverging CO SLEDs beyond J=4–3, and ultimately the different physical conditions in their molecular ISM. The much larger sensitivity of ALMA and its excellent site in the Atacama desert now allows the observations necessary to assess the dominant energy sources of the molecular gas and its mass in LIRGs without depending on the low-J CO lines.

scholarly journals Luminous Infrared Galaxies in a Merging Sequence: ISO Observations

1999 ◽  
Vol 186 ◽  
pp. 282-282 ◽  
Author(s):  
C.-Y. Hwang ◽  
K.Y. Lo ◽  
Y. Gao ◽  
R.A. Gruendl ◽  
N.-Y. Lu
Keyword(s):  
High Spatial Resolution ◽  
Molecular Gas ◽  
Infrared Images ◽  
Infrared Galaxies ◽  
Space Observatory ◽  
Infrared Space Observatory ◽  
Mid Infrared ◽  
Luminous Infrared Galaxies ◽  
Physical Conditions ◽  
Galaxy Interaction

We report mid-infrared images of several luminous infrared galaxies (LIGs) taken with ISOCAM on the Infrared Space Observatory (ISO). These LIGs were chosen to represent different phases of a merger sequence of galaxy-galaxy interaction with special emphasis on early/intermediate stages of merging. The molecular gas distribution of these LIGs has also been mapped at high spatial resolution (see contribution by Gao et al., this volume). The goal is to do a synoptic study of the evolution of physical conditions in these LIGs along the merger sequence.

scholarly journals Luminous IR Galaxies: Evolution and Molecular Gas

1997 ◽  
Vol 159 ◽  
pp. 439-440 ◽  
Author(s):  
Yu Gao
Keyword(s):  
Molecular Gas ◽  
Infrared Galaxies ◽  
Galaxy Interactions ◽  
Merging Galaxies ◽  
Star Forming ◽  
Luminous Infrared Galaxies ◽  
Star Forming Regions ◽  
Ir Sources ◽  
Order Of Magnitude ◽  
The Universe

Luminous infrared galaxies (LIRGs), denned by the criterion LIR ≳ 2 × 1011L⊙ (for H0=75 kms−1 Mpc−1), are the most powerful IR sources in the Universe, with most of their emission (~ 90%) in the far-IR. Most LIRGs are interacting/merging galaxies with large amounts of molecular gas as revealed by CO surveys (Sanders et al. 1991; Solomon et al. 1996). However, whether starbursts or dust-enshrouded AGNs/QSOs dominate the IR luminosity is not resolved.CO may not trace the active star-forming regions where gas density is more than one order of magnitude higher than the average. Dense molecular gas is better traced by high dipole-moment molecules like HCN and CS (e.g., Nguyen-Q-Rieu et al. 1992; Gao & Solomon 1996). Therefore, it is essential to survey HCN emission in a large sample of LIRGs to better reveal the nature of LIRGs. We here study IR and molecular gas properties vs. galaxy-galaxy interactions in LIRGs over various merging phases to trace their evolution and explore some links among interactions, starbursts, and AGN phenomena.

scholarly journals The molecular gas in luminous infrared galaxies - I. CO lines, extreme physical conditions and their drivers

2012 ◽  
Vol 426 (4) ◽  
pp. 2601-2629 ◽  
Author(s):  
Padelis P. Papadopoulos ◽  
Paul P. van der Werf ◽  
E. M. Xilouris ◽  
K. G. Isaak ◽  
Yu Gao ◽  
...  
Keyword(s):  
Molecular Gas ◽  
Infrared Galaxies ◽  
Luminous Infrared Galaxies ◽  
Physical Conditions

scholarly journals Mid-IR Spectroscopy of Submm Galaxies: Extended Star Formation in High-z Galaxies

2009 ◽  
Vol 5 (H15) ◽  
pp. 423-424
Author(s):  
K. Menéndez-Delmestre ◽  
A. W. Blain ◽  
I. Smail ◽  
D. M. Alexander ◽  
S. C. Chapman ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Dust Emission ◽  
Infrared Galaxies ◽  
Local Universe ◽  
Star Forming ◽  
Luminous Infrared Galaxies ◽  
Star Formation Activity ◽  
Polycyclic Aromatic ◽  
Intense Star Formation

AbstractUltra-luminous infrared galaxies (ULIRGs; L > 1012 L⊙) are quite rare in the local universe, but seem to dominate the co-moving energy density at z > 2. Many are optically-faint, dust-obscured galaxies that have been identified only relatively recently by the detection of their thermal dust emission redshifted into the sub-mm wavelengths. These submm galaxies (SMGs) have been shown to be a massive objects (M* ~ 1011 M⊙) undergoing intense star-formation(SFRs ~ 102 − 103 M⊙ yr−1) and the likely progenitors of massive ellipticals today. However, the AGN contribution to the far-IR luminosity had for years remained a caveat to these results. We used the Spitzer Infrared Spectrograph (IRS) to investigate the energetics of 24 radio-identified and spectroscopically-confirmed SMGs in the redshift range of 0.6 < z < 3.2. We find emission from Polycyclic Aromatic Hydrocarbons (PAHs) – which are associated with intense star-formation activity – in >80% of our sample and find that the median mid-IR spectrum is well described by a starburst component with an additional power-law continuum representing < 32% AGN contribution to the far-IR luminosity. We also find evidence for a more extended distribution of warm dust in SMGs compared to the more compact nuclear bursts in local ULIRGs and starbursts, suggesting that SMGs are not simple high-redshift analogs of local ULIRGs or nuclear starbursts, but have star formation which resembles that seen in less-extreme star-forming environments at z ~ 0.

scholarly journals THE MOLECULAR GAS IN LUMINOUS INFRARED GALAXIES. II. EXTREME PHYSICAL CONDITIONS AND THEIR EFFECTS ON THEXcoFACTOR

2012 ◽  
Vol 751 (1) ◽  
pp. 10 ◽  
Author(s):  
Padelis P. Papadopoulos ◽  
Paul van der Werf ◽  
E. Xilouris ◽  
Kate G. Isaak ◽  
Yu Gao
Keyword(s):  
Molecular Gas ◽  
Infrared Galaxies ◽  
Luminous Infrared Galaxies ◽  
Physical Conditions

scholarly journals ASCA Observations of Luminous Infrared Galaxies: Evolution from Starburst to AGN?

1999 ◽  
Vol 186 ◽  
pp. 341-344
Author(s):  
Takao Nakagawa ◽  
Tsuneo Kii ◽  
Ryuich Fujimoto ◽  
Toshiyuki Miyazaki ◽  
Hajime Inoue ◽  
...  
Keyword(s):  
Strong Interactions ◽  
Molecular Gas ◽  
Optimal Conditions ◽  
Infrared Galaxies ◽  
Local Universe ◽  
Luminous Infrared Galaxies ◽  
Show Evidence ◽  
Central Concentration

One of the most important results of the IRAS survey is the discovery of a class of “Luminous Infrared Galaxies” (LIGs), which emit most of the energy in the infrared and are the dominant population in the local universe at luminosities above 1011L⊙ (e.g., Sanders & Mirabel 1996). All LIGs appear to be extremely rich in molecular gas, and many of them show evidence of recent interacting/merging activities. Hence it is now accepted that strong interactions of gas-rich galaxies triggers large central concentration of molecular gas, and makes optimal conditions for both enormous nuclear starbursts and building and/or fueling AGN. Actually, various observations show evidence of starburst activity as well as that of AGN in many LIGs (Sanders & Mirabel 1996).

scholarly journals Molecular Gas Excitation and Chemistry in VV 114 and NGC 1614 with ALMA

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Toshiki Saito ◽  
Daisuke Iono ◽  
Junko Ueda ◽  
Min S. Yun ◽  
Kouichiro Nakanishi ◽  
...  
Keyword(s):  
Band 3 ◽  
Molecular Gas ◽  
Infrared Galaxies ◽  
Molecular Line ◽  
Luminous Infrared Galaxies ◽  
Physical Conditions ◽  
Spatial Properties ◽  
Processing Line ◽  
Molecular Lines ◽  
Line Imaging

AbstractWe present high resolution molecular line observations of dusty AGN and starburst in nearby luminous infrared galaxies (LIRGs), VV 114 (band 3/4/7) and NGC 1614 (band 3/6/7/9), with ALMA. Multi-frequency imaging from 4.8 GHz to 691 GHz of NGC 1614 allows us to study spatial properties of the radio-to-FIR continuum and multiple CO transitions, and we find the CO excitation up to Jupp = 6 can be explained by a single ISM model powered by nuclear starbursts. Our processing line imaging survey for VV 114 detected at least 30 molecular lines which show different chemical composition from region to region. Multi-molecule imaging helps us to diagnose the chemical differences of dusty ISM, while multi-transition imaging allows us to investigate gas physical conditions affected by nuclear activities directly.

scholarly journals A Herschel Spectroscopic Survey of Warm Molecular Gas in Local Infrared Luminous Galaxies

2012 ◽  
Vol 8 (S292) ◽  
pp. 249-249
Author(s):  
N. Lu ◽  
Y. Zhao ◽  
C. K. Xu ◽  
Y. Gao ◽  
Keyword(s):  
Fourier Transform ◽  
Spectral Line ◽  
Molecular Gas ◽  
Fourier Transform Spectrometer ◽  
Infrared Galaxies ◽  
Limited Sample ◽  
Line Energy ◽  
Luminous Infrared Galaxies ◽  
Luminous Galaxies ◽  
J 13

AbstractWe describe an on-going 194-671 μm spectroscopic survey of a flux-limited sample of 125 local luminous infrared galaxies (LIRGs) with Herschel SPIRE Fourier Transform Spectrometer (FTS). The survey targets primarily the CO spectral line energy distribution (SLED), from J = 4-3 up to J = 13-12, to probe dense and warm molecular gas that should play an intimate role in star formation and/or active galactic nuclear activities in these galaxies. The program is about 75% finished. At S/N > 5, besides the CO lines, we also detected [N ii] 205 μm and [C i] 370 μm (3P2 − 3P1) lines in every target observed. In about half of the observed targets, we also detected [C i] 609 μm (3P1 – 3P0).

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