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 A Study of the Distribution of Star-forming Regions in Luminous Infrared Galaxies by Means of H Imaging Observations

2004 ◽  
Vol 127 (2) ◽  
pp. 736-757 ◽  
Author(s):  
T. Hattori ◽  
M. Yoshida ◽  
H. Ohtani ◽  
H. Sugai ◽  
T. Ishigaki ◽  
...  
Keyword(s):  
Infrared Galaxies ◽  
Star Forming ◽  
Luminous Infrared Galaxies ◽  
Star Forming Regions

scholarly journals A Very Large Array Survey of Luminous Extranuclear Star-forming Regions in Luminous Infrared Galaxies in GOALS

2019 ◽  
Vol 881 (1) ◽  
pp. 70 ◽  
Author(s):  
S. T. Linden ◽  
Y. Song ◽  
A. S. Evans ◽  
E. J. Murphy ◽  
L. Armus ◽  
...  
Keyword(s):  
Large Array ◽  
Infrared Galaxies ◽  
Very Large Array ◽  
Star Forming ◽  
Luminous Infrared Galaxies ◽  
Star Forming Regions

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 The Nature of the Energy Source in LINERs

1997 ◽  
Vol 159 ◽  
pp. 477-484
Author(s):  
L. Colina ◽  
A. Koratkar
Keyword(s):  
Minor Role ◽  
Host Galaxies ◽  
Infrared Galaxies ◽  
Star Forming ◽  
Luminous Infrared Galaxies ◽  
Star Forming Regions ◽  
Resolution Imaging ◽  
Imaging And Spectroscopy ◽  
A Minor ◽  
High Spatial Resolution Imaging

AbstractLINERs are found in ~30% of all bright galaxies, including luminous infrared galaxies. They form a heterogeneous class powered by a variety of ionizing mechanisms such as low-luminosity AGNs, starbursts, shocks, or any combination of these.In early-type spirals, LINERs are powered by a low-luminosity AGN, or by an AGN surrounded by circumnuclear star-forming regions. In luminous infrared galaxies, LINERs are powered by starbursts with associated wind-related extended shocks, and an AGN may play a minor role, if any. LINERs in some FR I radio galaxies show a strong evidence for the presence of a massive central black hole, and there are indications for the existence of shocks in the nuclear disks of these galaxies. Yet, the dominant ionizing mechanism for LINERs in radio-quiet ellipticals and FR I host galaxies is still unclear.Multifrequency high spatial resolution imaging and spectroscopy are essential to discriminate among the different ionizing mechanisms present in LINERs.

scholarly journals The ALMaQUEST Survey: VI. The molecular gas main sequence of ‘retired’ regions in galaxies.

2020 ◽  
Author(s):  
Sara L Ellison ◽  
Lihwai Lin ◽  
Mallory D Thorp ◽  
Hsi-An Pan ◽  
Sebastian F Sánchez ◽  
...  
Keyword(s):  
Main Sequence ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Gas Main ◽  
The Galaxy ◽  
Order Of Magnitude ◽  
Using Data ◽  
Gas Fractions

Abstract In order to investigate the role of gas in the demise of star formation on kpc-scales, we compare the resolved molecular gas main sequence (rMGMS: $\Sigma _{\rm H_2}$ vs Σ⋆) of star-forming regions to the sequence of ‘retired’ regions that have ceased to form new stars. Using data from the ALMaQUEST survey, we find that retired spaxels form a rMGMS that is distinct from that of star-forming spaxels, offset to lower $\Sigma _{\rm H_2}$ at fixed Σ⋆ by a factor of ∼5. We study the rMGMS of star-forming and retired spaxels on a galaxy-by-galaxy basis for eight individual ALMaQUEST galaxies. Six of these galaxies have their retired spaxels concentrated within the central few kpc. Molecular gas is detected in 40-100% of retired spaxels in the eight galaxies in our sample. Both the star-forming and retired rMGMS show a diversity in normalization from galaxy-to-galaxy. However, in any given galaxy, the rMGMS for retired regions is found to be distinct from the star-forming sequence and gas fractions of retired spaxels are up to an order of magnitude lower than the star-forming spaxels. We conclude that quenching is associated with a depletion (but not absence) of molecular gas via a mechanism that typically begins in the centre of the galaxy.

Characterizing circumnuclear starbursts in the local universe with the VLA

2020 ◽  
Vol 15 (S359) ◽  
pp. 462-463
Author(s):  
Yiqing Song ◽  
Sean T. Linden ◽  
Aaron S. Evans ◽  
Loreto Barcos-Muñoz ◽  
Eric J. Murphy
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Radio Continuum ◽  
Infrared Galaxies ◽  
Very Large Array ◽  
Star Forming ◽  
Luminous Infrared Galaxies ◽  
Normal Galaxies ◽  
Star Forming Regions ◽  
Nuclear Ring

AbstractNuclear rings are excellent laboratories to study star formation (SF) under extreme conditions. We compiled a sample of 9 galaxies that exhibit bright nuclear rings at 3-33 GHz radio continuum observed with the Jansky Very Large Array, of which 5 are normal star-forming galaxies and 4 are Luminous Infrared Galaxies (LIRGs). Using high frequency radio continuum as an extinction-free tracer of SF, we estimated the size and star formation rate of each nuclear ring and a total of 37 individual circumnuclear star-forming regions. Our results show that majority of the SF in the sample LIRGs take place in their nuclear rings, and circumnuclear SF in local LIRGs are much more spatially concentrated compared to those in the local normal galaxies and previously studied nuclear and extra-nuclear SF in normal galaxies at both low and high redshifts.

scholarly journals Resolved star formation relations at high redshift from the IRAM PHIBSS program

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Jonathan Freundlich ◽  
Françoise Combes ◽  
Linda Tacconi ◽  
Michael Cooper ◽  
Reinhard Genzel ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Formation Rate ◽  
Molecular Gas ◽  
Formation Processes ◽  
Massive Galaxies ◽  
Star Forming ◽  
Star Forming Regions ◽  
Order Of Magnitude ◽  
Formation Efficiency

AbstractObserved massive galaxies in the distant Universe form stars at much higher rates than today. High levels of star formation are sustained by a continuous supply of fresh gas and high molecular gas fractions. But after a peak around redshift z=2-3, the star formation rate decreases by an order of magnitude. Is this evolution mostly driven by the available cold gas reservoir, or are the star formation processes qualitatively different near the star formation peak? The Kennicutt-Schmidt relation enables to characterize the star formation efficiency at low and high redshift, but resolved measurements at the scale of the star-forming regions themselves are still challenging at high redshift. Molecular gas observations carried out at the IRAM Plateau de Bure interferometer within the PHIBSS program (Tacconi, Combes et al.) permit us to study the star formation efficiency at sub-galactic scales around z=1.2 and 1.5 for a limited sample of galaxies, and thus help characterize the star formation processes at this epoch. Our results lay in the continuation of the resolved low-redshift measurements, but further studies would be necessary to complement our sample and validate our conclusions.

scholarly journals Molecular gas and star formation activity in luminous infrared galaxies in clusters at intermediate redshifts

2020 ◽  
Vol 640 ◽  
pp. A64 ◽  
Author(s):  
G. Castignani ◽  
P. Jablonka ◽  
F. Combes ◽  
C. P. Haines ◽  
T. Rawle ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Fraction ◽  
Spectral Energy Distribution ◽  
Cluster Core ◽  
Spectral Energy ◽  
Molecular Gas ◽  
Infrared Galaxies ◽  
Local Cluster ◽  
Star Forming ◽  
Luminous Infrared Galaxies

We investigate the role of dense megaparsec-scale environments in processing molecular gas of cluster galaxies as they fall into the cluster cores. We selected a sample of ∼20 luminous infrared galaxies (LIRGs) belonging to intermediate-redshift clusters, mainly from the Herschel Lensing Survey and the Local Cluster Substructure Survey. These galaxies include MACS J0717.5+3745 at z = 0.546 and Abell 697, 963, 1763, and 2219 at z = 0.2 − 0.3. We performed spectral energy distribution modeling from the far-infrared to ultraviolet of the LIRGs, which span cluster-centric distances within r/r200 ≃ 0.2 − 1.6. We observed the LIRGs in CO(1→0) or CO(2→1) with the Plateau de Bure interferometer and its successor NOEMA, as part of five observational programs carried out between 2012 and 2017. We compared the molecular gas to stellar mass ratio M(H2)/M⋆, star formation rate (SFR), and depletion time (τdep) of the LIRGs with those of a compilation of cluster and field star-forming galaxies from the literature. The targeted LIRGs have SFR, M(H2)/M⋆, and τdep that are consistent with those of both main-sequence (MS) field galaxies and star-forming galaxies from the comparison sample. However we find that the depletion time, normalized to the MS value, tentatively increases with increasing r/r200, with a significance of 2.8σ, which is ultimately due to a deficit of cluster-core LIRGs with τdep ≳ τdep, MS. We suggest that a rapid exhaustion of the molecular gas reservoirs occurs in the cluster LIRGs and is indeed effective in suppressing their star formation and ultimately quenching them. This mechanism may explain the exponential decrease of the fraction of cluster LIRGs with cosmic time. The compression of the gas in LIRGs, possibly induced by intra-cluster medium shocks, may be responsible for the short timescales that are observed in a large fraction of cluster-core LIRGs. Some of our LIRGs may also belong to a population of infalling filament galaxies.

scholarly journals X-Ray Coronae from Stars

1998 ◽  
Vol 188 ◽  
pp. 13-16
Author(s):  
R. Pallavicini
Keyword(s):  
Open Clusters ◽  
Temperature Structure ◽  
List Type ◽  
Star Forming ◽  
Spectroscopic Observations ◽  
Star Forming Regions ◽  
Complete Mapping ◽  
Sky Survey ◽  
Order Of Magnitude ◽  
Age Range

A number of major advances in stellar coronal physics have occurred since 1990 mainly as a consequence of imaging observations by ROSAT and spectroscopic observations by ASCA. These can be summarised as follows: 1.an all-sky survey has been performed by ROSAT at a sensitivity of ~ 2 × 10−13 erg cm−2 s−1, complemented by pointed observations an order of magnitude deeper;2.complete mapping and deeper pointings have been obtained for virtually all open clusters closer than ~ 500 pc, and covering the age range from ~ 30 Myr to ~ 700 Myr;3.complete mapping and deeper paintings have been obtained for several Star Forming Regions (SFRs) covering the age range ~ 1 to ~ 10 Myr;4.spectroscopic observations of bright coronal sources have been obtained with EUVE and ASCA allowing the derivation of the temperature structure and elemental abundances.

Sign in / Sign up

Export Citation Format

Share Document