Dense molecular gas in star-forming regions — The importance of submillimeter observations

2008 ◽  
pp. 150-163 ◽  
Author(s):  
Karl M. Menten
Keyword(s):  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals The Connection between Molecular Gas and Star Formation in XUV Disks

2016 ◽  
Vol 11 (S321) ◽  
pp. 214-216
Author(s):  
Linda C. Watson
Keyword(s):  
Star Formation ◽  
Molecular Hydrogen ◽  
Optical Disk ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions

AbstractWe found that star-forming regions in extended ultraviolet (XUV) disks are generally consistent with the molecular-hydrogen Kennicutt-Schmidt law that applies within the inner, optical disk. This is true for star formation rates based on Hα + 24 μm data or FUV + 24 μm data. We estimated that the star-forming regions have ages of 1 − 7 Myr and propose that the presence or absence of molecular gas provides an additional “clock” that may help distinguish between aging and stochasticity as the explanation for the low Hα-to-FUV flux ratios in XUV disks. This contribution is a summary of the work originally presented in Watson et al. (2016).

scholarly journals Shocked Molecular Hydrogen from Star Forming Regions

1987 ◽  
Vol 115 ◽  
pp. 181-181 ◽  
Author(s):  
Adair P. Lane ◽  
John Bally
Keyword(s):  
Shock Waves ◽  
High Velocity ◽  
Molecular Hydrogen ◽  
Near Infrared ◽  
Young Stars ◽  
Emission Lines ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Post Shock

Near infrared (2 micron) emission lines from molecular hydrogen provide a powerful probe of the morphology and energetics of outflows associated with stellar birth. The H2 emission regions trace the location of shock waves formed when the high velocity outflow from young stars encounters dense quiescent gas. Since H2 is the dominant coolant of the hot post-shock molecular gas, the H2 lines provide a measure of the fraction of the total mechanical luminosity radiated away from the cloud.

scholarly journals Are interstellar ices porous, and how do the pores collapse?

2015 ◽  
Vol 11 (A29A) ◽  
Author(s):  
C. R. Hill ◽  
C. Mitterdorfer ◽  
T. G. A. Youngs ◽  
D. T. Bowron ◽  
N. Pascual ◽  
...  
Keyword(s):  
Solar System ◽  
Amorphous Solid ◽  
Growth Conditions ◽  
Molecular Gas ◽  
Pore Collapse ◽  
Star Forming ◽  
Gas Phases ◽  
Star Forming Regions ◽  
Solar System Objects ◽  
Interstellar Ices

Amorphous solid water (ASW) is of great importance in astrochemistry as it has been detected in star forming regions, comets, and cold solar-system objects. A key property of ASW is its porous nature (with the extent of porosity reflecting the formation and growth conditions) and the subsequent pore collapse when the ice is heated. If interstellar ices are porous there are huge implications to both the process of planet formation and the budgets of molecular gas in the solid and gas phases. It is therefore vital to understand ASW porosity over astronomically relevant conditions in order to effectively model its potential effects on these processes.

scholarly journals Molecular Gas in the Magellanic Clouds

1999 ◽  
Vol 190 ◽  
pp. 67-73 ◽  
Author(s):  
Mónica Rubio
Keyword(s):  
Line Emission ◽  
Magellanic Clouds ◽  
Gas Content ◽  
Molecular Gas ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Hydrogen Column Density ◽  
Spatial Coverage ◽  
Co Emission

The molecular gas content in the Magellanic Clouds has been studied, with different spatial coverage and resolution, through obervations of CO(1-0) line emission. In the LMC and the SMC the molecular gas is dominated by clouds whose properties are different from those of their Galactic counterparts. The relation between the intensity of CO emission and molecular hydrogen column density, or the conversion factor X, is different than that of molecular clouds in our Galaxy and depends on the ambient physical conditions. Studying the molecular gas through observations in the H2 emission line may prove an alternative way to determine the molecular content associated with star forming regions in the Magellanic Clouds. In particular, results obtained towards 30 Doradus in the LMC are presented.

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 High-J CO Intensity Measurements for Galaxies Observed by the Herschel FTS

2015 ◽  
Vol 11 (S315) ◽  
pp. 26-29
Author(s):  
Julia Kamenetzky ◽  
Naseem Rangwala ◽  
Jason Glenn ◽  
Philip Maloney ◽  
Alex Conley
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Raw Material ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
J 13 ◽  
Systematic Effects ◽  
Nearby Galaxies ◽  
Co Emission

AbstractMolecular gas is the raw material for star formation and is commonly traced by the carbon monoxide (CO) molecule. The atmosphere blocks all but the lowest-J transitions of CO for observatories on the ground, but the launch of the Herschel Space Observatory revealed the CO emission of nearby galaxies from J = 4−3 to J = 13−12. Herschel showed that mid- and high-J CO lines in nearby galaxies are emitted from warm gas, accounting for approximately 10% of the molecular mass, but the majority of the CO luminosity. The energy budget of this warm, highly-excited gas is a significant window into the feedback interactions among molecular gas, star formation, and galaxy evolution. Likely, mechanical heating is required to explain the excitation. Such gas has also been observed in star forming regions within our galaxy.We have examined all ~300 spectra of galaxies from the Herschel Fourier Transform Spectrometer and measured line fluxes or upper limits for the CO J = 4−3 to J = 13−12, [CI], and [NII] 205 micron lines in ~200 galaxies, taking systematic effects of the FTS into account. We will present our line fitting method, illustrate trends available so far in this large sample, and preview the full 2-component radiative transfer likelihood modeling of the CO emission using an illustrative sample of 20 galaxies, including comparisons to well-resolved galactic regions. This work is a comprehensive study of mid- and high-J CO emission among a variety of galaxy types, and can be used as a resource for future (sub)millimeter studies of galaxies with ground-based instruments.

scholarly journals A VLBI Study of H2O Maser Spots Associated with a Molecular Outflow ρ Oph-East

1994 ◽  
Vol 140 ◽  
pp. 60-61
Author(s):  
Takahiro Iwata ◽  
Hiroshi Takaba ◽  
Kin-Ya Matsumoto ◽  
Seiji Kameno ◽  
Noriyuki Kawaguchi
Keyword(s):  
Molecular Cloud ◽  
Observational Evidence ◽  
Molecular Gas ◽  
Mass Star ◽  
Dynamical Interaction ◽  
Star Forming ◽  
Star Forming Regions ◽  
Molecular Outflow ◽  
Low Mass ◽  
A Site

A molecular outflow is one of the most conspicuous active phenomena associated with protostars, and the kinetic energy of its outflowing mass is as large as that of random motions of ambient molecular cloud, which suggests that outflow has dynamically influence on ambient molecular gas. Possible observational evidence which suggests the existence of dynamical interaction between molecular outflow and ambient molecular cloud has been detected in several star forming regions (Fukui et al. 1986; Iwata et al. 1988). Recent detections of H2O maser emission associated with low-mass protostars (e.g. Comoretto et al. 1990) also suggest that there still exist active phenomena in the low-mass star forming regions.Molecular outflow ρ Oph-East, discovered toward a low-mass protostar IRAS 16293-2422 (Fukui et al. 1986), has been known as a site of dynamical interaction between molecular outflowing gas and ambient molecular cloud by CO and NH3 observation (Mizuno et al. 1990). Existence of several strong H2O maser spots (Wilking & Claussen 1987; Wotten 1989; Terebey et al. 1992) also suggests that active phenomena are occurring in this region. In this paper, we report our result of H2O maser observation for molecular outflow ρ Oph-East with milli-arcsecond resolution by VLBI.

scholarly journals Properties of star forming regions in the Magellanic Clouds

2008 ◽  
Vol 4 (S256) ◽  
pp. 215-226
Author(s):  
Mónica Rubio
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Molecular Clouds ◽  
Massive Star ◽  
High Sensitivity ◽  
Magellanic Clouds ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Metallicity

AbstractUnderstanding the process of star formation in low metallicity systems is one of the key studies in the early stages of galaxy evolution. The Magellanic Clouds, being the nearest examples of low metallicity systems, allow us to study in detail their star forming regions. As a consequence of their proximity we can resolve the molecular clouds and the regions of star formation individually. Therefore we can increase our knowledge of the interaction of young luminous stars with their environment. We will present results of multiwavelenghts studies of LMC and SMC massive star forming regions, which includes properties of the cold molecular gas, the embedded young population associated with molecular clouds, and the interaction of newly born stars with the surrounding interstellar medium, based on ASTE and APEX submillimeter observations complemented high sensitivity NIR groud based observations and Spitzer results.

scholarly journals Intense velocity-shears and magnetic fields in diffuse molecular gas: from 10 pc to 5 mpc

2009 ◽  
Vol 5 (H15) ◽  
pp. 442-443
Author(s):  
Edith Falgarone ◽  
Pierre Hily-Blant
Keyword(s):  
Velocity Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Dust Emission ◽  
Large Scale Structure ◽  
Small Scale ◽  
Molecular Gas ◽  
Gas Velocity ◽  
Star Forming ◽  
Star Forming Regions

AbstractRegions of intense velocity-shears are identified on statistical grounds in nearby diffuse molecular gas: they form conspicuous thin (~ 0.03 pc) and parsec-long structures that do not bear the signatures of shocked gas. Several straight substructures, ~ 3 mpc thick, have been detected at different position-angles within one of them. Two exhibit the largest velocity-shears ever measured far from star forming regions, up to 780 kms−1pc−1. Their position-angles are found to be also those of 10-parsec striations in the I(100μm) dust emission of the large scale environment. The B field projections, where available in these fields, are parallel both to the parsec- and to one of the milliparsec-scale shears. These findings put in relation the small-scale intermittent facet of the gas velocity field and the large scale structure of the magnetic fields.

scholarly journals Inefficient jet-induced star formation in Centaurus A

2017 ◽  
Vol 608 ◽  
pp. A98 ◽  
Author(s):  
Q. Salomé ◽  
P. Salomé ◽  
M.-A. Miville-Deschênes ◽  
F. Combes ◽  
S. Hamer
Keyword(s):  
Star Formation ◽  
Positive Feedback ◽  
Molecular Clouds ◽  
Milky Way ◽  
Data Cube ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Co Emission ◽  
Centaurus A

NGC 5128 (Centaurus A) is one of the best targets to study AGN feedback in the local Universe. At 13.5 kpc from the galaxy, optical filaments with recent star formation lie along the radio jet direction. This region is a testbed for positive feedback, here through jet-induced star formation. Atacama Pathfinder EXperiment (APEX) observations have revealed strong CO emission in star-forming regions and in regions with no detected tracers of star formation activity. In cases where star formation is observed, this activity appears to be inefficient compared to the Kennicutt-Schmidt relation. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to map the 12CO(1–0) emission all along the filaments of NGC 5128 at a resolution of 1.3′′ ~ 23.8pc. We find that the CO emission is clumpy and is distributed in two main structures: (i) the Horseshoe complex, located outside the HI cloud, where gas is mostly excited by shocks and where no star formation is observed, and (ii) the Vertical filament, located at the edge of the HI shell, which is a region of moderate star formation. We identified 140 molecular clouds using a clustering method applied to the CO data cube. A statistical study reveals that these clouds have very similar physical properties, such as size, velocity dispersion, and mass, as in the inner Milky Way. However, the range of radius available with the present ALMA observations does not enable us to investigate whether or not the clouds follow the Larson relation. The large virial parameter αvir of the clouds suggests that gravity is not dominant and clouds are not gravitationally unstable. Finally, the total energy injection in the northern filaments of Centaurus A is of the same order as in the inner part of the Milky Way. The strong CO emission detected in the northern filaments is an indication that the energy injected by the jet acts positively in the formation of dense molecular gas. The relatively high virial parameter of the molecular clouds suggests that the injected kinetic energy is too strong for star formation to be efficient. This is particularly the case in the horseshoe complex, where the virial parameter is the largest and where strong CO is detected with no associated star formation. This is the first evidence of AGN positive feedback in the sense of forming molecular gas through shocks, associated with low star formation efficiency due to turbulence injection by the interaction with the radio jet.

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