scholarly journals The H ii Region/PDR Connection: Self‐consistent Calculations of Physical Conditions in Star‐forming Regions

2005 ◽  
Vol 161 (1) ◽  
pp. 65-95 ◽  
Author(s):  
N. P. Abel ◽  
G. J. Ferland ◽  
G. Shaw ◽  
P. A. M. van Hoof
Keyword(s):  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Self Consistent ◽  
H Ii Region

scholarly journals NGC628 with SITELLE: I. Imaging spectroscopy of 4285 H ii region candidates

2018 ◽  
Vol 477 (3) ◽  
pp. 4152-4186 ◽  
Author(s):  
L Rousseau-Nepton ◽  
C Robert ◽  
R P Martin ◽  
L Drissen ◽  
T Martin
Keyword(s):  
Imaging Spectroscopy ◽  
Morphological Type ◽  
H Ii Regions ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Wide Range ◽  
Nearby Galaxies ◽  
H Ii Region ◽  
The Individual

Abstract This is the first paper of a series dedicated to nebular physics and the chemical evolution of nearby galaxies by investigating large samples of H ii regions with the Canada–France–Hawaii Telescope imaging spectrograph SITELLE (Spectro-Imageur à Transformée de Fourier pour l’Étude en Long et en Large des raies d’Émission). We present a technique adapted to imaging spectroscopy to identify and extract parameters from 4285 H ii region candidates found in the disc of NGC 628. Using both the spatial and spectral capabilities of SITELLE, our technique enables the extraction of the position, dust extinction, velocity, H α profile, diffuse ionized gas (DIG) background, luminosity, size, morphological type, and the emission-line fluxes for individual spaxels and the integrated spectrum for each region. We have produced a well-sampled H ii region luminosity function and studied its variation with galactocentric radius and level of the DIG background. We found a slope α of −1.12 ± 0.03 with no evidence of a break at high luminosity. Based on the width of the region profile, bright regions are rather compact, while faint regions are seen over a wide range of sizes. The radius function reveals a slope of −1.81 ± 0.02. BPT diagrams of the individual spaxels and integrated line ratios confirm that most detections are H ii regions. Also, maps of the line ratios show complex variations of the ionization conditions within H ii regions. All this information is compiled in a new catalogue for H ii regions. The objective of this data base is to provide a complete sample which will be used to study the whole parameter space covered by the physical conditions in active star-forming regions.

scholarly journals Massive star population in circumnuclear star-forming regions

2003 ◽  
Vol 212 ◽  
pp. 537-538
Author(s):  
Mar Álvarez-Álvarez ◽  
Ángeles I. Díaz ◽  
Marcelo Castellanos
Keyword(s):  
Massive Star ◽  
Stellar Populations ◽  
H Ii Regions ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Spectrophotometric Data ◽  
H Ii Region ◽  
Formation And Evolution ◽  
Photo Ionization

Due to their high luminosity, the importance of understanding the massive star formation and evolution of giant Hii regions has become more and more evident in the last few years. A mayor scenario where giant H ii regions form and develop are the very inner parts of some galaxies. These bursts frequently are arranged in a ring-like pattern. We present a study of the stellar populations and gas physical conditions in circumnuclear star-forming regions (CNSFR) based on broad- and narrow-band photometry and spectrophotometric data, which have been analyzed with the use of evolutionary population synthesis and photo-ionization models. It is found that most CNSFRs show composite stellar populations of slightly different ages. They seem to have the highest abundances found in H ii region-like objects, showing also N/O overabundances and S/O underabundaces by a factor of about three. Also, CNSFRs as a class segregate from the disk H ii region family, clustering around higher ionizing temperatures.

scholarly journals Millimetre wavelength methanol masers survey towards massive star forming regions

2007 ◽  
Vol 3 (S242) ◽  
pp. 234-235
Author(s):  
T. Umemoto ◽  
N. Mochizuki ◽  
K. M. Shibata ◽  
D.-G. Roh ◽  
H.-S. Chung
Keyword(s):  
Detection Rate ◽  
Massive Star ◽  
Molecular Line ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Maser Sources

AbstractWe present the results of a mm wavelength methanol maser survey towards massive star forming regions. We have carried out Class II methanol maser observations at 86.6 GHz, 86.9 GHz and 107.0 GHz, simultaneously, using the Nobeyama 45 m telescope. We selected 108 6.7 GHz methanol maser sources with declinations above −25 degrees and fluxes above 20 Jy. The detection limit of maser observations was ~3 Jy. Of the 93 sources surveyed so far, we detected methanol emission in 25 sources (27%) and “maser” emission in nine sources (10%), of which thre “maser” sources are new detections. The detection rate for maser emission is about half that of a survey of the southern sky (Caswell et al. 2000). There is a correlation between the maser flux of 107 GHz and 6.7 GHz/12 GHz emission, but no correlation with the “thermal” (non maser) emission. From results of other molecular line observations, we found that the sources with methanol emission show higher gas temperatures and twice the detection rate of SiO emission. This may suggest that dust evaporation and destruction by shock are responsible for the high abundance of methanol molecules, one of the required physical conditions for maser emission.

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 Warm gas in protostellar outflows

2019 ◽  
Vol 629 ◽  
pp. A77
Author(s):  
A. I. Gómez-Ruiz ◽  
A. Gusdorf ◽  
S. Leurini ◽  
K. M. Menten ◽  
S. Takahashi ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
High Velocity ◽  
The Other ◽  
Mass Star ◽  
Intermediate Mass ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Low Mass ◽  
Kinematic Properties

Context. OMC-2/3 is one of the nearest embedded cluster-forming regions that includes intermediate-mass protostars at early stages of evolution. A previous CO (3–2) mapping survey towards this region revealed outflow activity related to sources at different evolutionary phases. Aims. The present work presents a study of the warm gas in the high-velocity emission from several outflows found in CO (3–2) emission by previous observations, determines their physical conditions, and makes a comparison with previous results in low-mass star-forming regions. Methods. We used the CHAMP+ heterodyne array on the APEX telescope to map the CO (6–5) and CO (7–6) emission in the OMC-2 FIR 6 and OMC-3 MMS 1-6 regions, and to observe 13CO (6–5) at selected positions. We analyzed these data together with previous CO (3–2) observations. In addition, we mapped the SiO (5–4) emission in OMC-2 FIR 6. Results. The CO (6–5) emission was detected in most of the outflow lobes in the mapped regions, while the CO (7–6) was found mostly in the OMC-3 outflows. In the OMC-3 MMS 5 outflow, a previously undetected extremely high-velocity gas was found in CO (6–5). This extremely high-velocity emission arises from the regions close to the central object MMS 5. Radiative transfer models revealed that the high-velocity gas from MMS 5 outflow consists of gas with nH2 = 104–105 cm−3 and T > 200 K, similar to what is observed in young Class 0 low-mass protostars. For the other outflows, values of nH2 > 104 cm−3 were found. Conclusions. The physical conditions and kinematic properties of the young intermediate-mass outflows presented here are similar to those found in outflows from Class 0 low-mass objects. Due to their excitation requirements, mid − J CO lines are good tracers of extremely high-velocity gas in young outflows likely related to jets.

scholarly journals Models of Gas-Grain Chemistry in Star-forming Regions

2000 ◽  
Vol 197 ◽  
pp. 147-159 ◽  
Author(s):  
Eric Herbst
Keyword(s):  
Temporal Variations ◽  
Binding Energies ◽  
Dust Particles ◽  
Temperature Phase ◽  
Mathematical Treatment ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Chemical Models ◽  
Key Species

It is difficult if not impossible to explain the abundances of assorted interstellar molecules in both the gaseous and condensed phases without the use of grain chemistry. Unfortunately, the chemistry occurring on grains is not well understood because of a variety of uncertainties including the nature, size, and shape of dust particles, the binding energies of key species, the dominant mechanism of surface chemistry, and the correct mathematical treatment of surface processes. Still, intrepid astrochemists have used granular chemistry in chemical models of an assortment of sources including cold clouds, protostellar disks, and hot cores. Indeed, the dominant explanation of the saturated gas-phase molecules observed in hot cores involves grain chemistry during an earlier, low temperature phase. Although gas-grain models have elucidated major features of the chemistry, much more work remains to be accomplished before they can be used to help characterize the physical conditions in star-forming regions and their temporal variations.

5 Centimeter OH Masers as Diagnostics of Physical Conditions in Star‐forming Regions

2000 ◽  
Vol 534 (2) ◽  
pp. 770-780 ◽  
Author(s):  
Konstantinos G. Pavlakis ◽  
Nikolaos D. Kylafis
Keyword(s):  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions

scholarly journals Chemistry in the Envelopes around Massive Young Stars

2002 ◽  
Vol 12 ◽  
pp. 146-148
Author(s):  
Ewine F. van Dishoeck ◽  
Floris F.S. van der Tak
Keyword(s):  
Young Star ◽  
Young Stars ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Chemical Studies ◽  
H Ii Region ◽  
Infrared Wavelengths ◽  
Collapse Phase

AbstractRecent chemical studies of high-mass star-forming regions at submillimeter and infrared wavelengths reveal large variations in the abundances depending on evolutionary state. Such variations can be explained by freezing out of molecules onto grains in the cold collapse phase, followed by evaporation and high-temperature chemical reactions when the young star heats the envelope. Thus, the chemical composition can be a powerful diagnostic tool. A detailed study of a set of infrared-bright massive young stars reveals systematic increases in the gas/solid ratios and abundances of evaporated molecules with temperature. This ‘global heating’ plausibly results from the gradual dispersion of the envelopes. We argue that these objects form the earliest phase of massive star formation, before the ‘hot core’ and ultracompact H II region phase.

scholarly journals LBA observations of OH masers in the star-forming region OH 330.953–0.182

2007 ◽  
Vol 3 (S242) ◽  
pp. 162-163
Author(s):  
B. Hutawarakorn Kramer ◽  
J. L. Caswell ◽  
A. Sukom ◽  
J. E. Reynolds
Keyword(s):  
Magnetic Field ◽  
Excited State ◽  
Ground State ◽  
State Transitions ◽  
Star Forming ◽  
Left Hand ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Long Baseline ◽  
Right And Left Hand

AbstractOH masers are sensitive probes of the kinematics, physical conditions, and magnetic fields in star-forming regions. The maser site OH 330.953-0.182 has been studied using the Long Baseline Array of the Australia Telescope National Facility. Simultaneous observations of the 1665- and 1667-MHz hydroxyl ground-state transitions yield a series of maps at velocity spacing 0.09kms−1, in both right- and left-hand circular polarization, with tenth-arcsec spatial resolution. Several clusters of maser spots have been detected within a five-arcsec region. Eight Zeeman pairs were found, and in one case, at 1665 MHz, there is a nearby 1667-MHz pair indicating a similar value of magnetic field and velocity. Over the whole site, all magnetic field estimates are toward us (negative), and range from -3.7 to -5.8 mG. We also compared the morphology and kinematics of the 1665- and 1667-MHz maser spots with those from the excited state of OH at 6035 MHz and from methanol at 6668 MHz.

Sign in / Sign up

Export Citation Format

Share Document