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 The case for thermalization as a contributor to the [C ii] deficit

2021 ◽  
Vol 503 (1) ◽  
pp. 911-919
Author(s):  
Jessica Sutter ◽  
Daniel A Dale ◽  
Karin Sandstrom ◽  
J D T Smith ◽  
Alberto Bolatto ◽  
...  
Keyword(s):  
Far Infrared ◽  
Infrared Emission ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Observable Universe ◽  
Star Forming ◽  
Star Forming Regions ◽  
Wide Range ◽  
Nearby Galaxies ◽  
Selection Of

ABSTRACT The [C ii] deficit, which describes the observed decrease in the ratio of [C ii] 158 μm emission to continuum infrared emission in galaxies with high star formation surface densities, places a significant challenge to the interpretation of [C ii] detections from across the observable universe. In an attempt to further decode the cause of the [C ii] deficit, the [C ii] and dust continuum emission from 18 Local Volume galaxies has been split based on conditions within the interstellar medium where it originated. This is completed using the Key Insights in Nearby Galaxies: a Far-Infrared Survey with Herschel (KINGFISH) and Beyond the Peak (BtP) surveys and the wide-range of wavelength information, from UV to far-infrared emission lines, available for a selection of star-forming regions within these samples. By comparing these subdivided [C ii] emissions to isolated infrared emission and other properties, we find that the thermalization (collisional de-excitation) of the [C ii] line in H ii regions plays a significant role in the deficit observed in our sample.

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 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 Characteristics of H2CO Towards Star-Forming Regions

1987 ◽  
Vol 115 ◽  
pp. 171-171
Author(s):  
H. R. Dickel ◽  
W. M. Goss ◽  
A. H. Rots
Keyword(s):  
Molecular Clouds ◽  
H Ii Regions ◽  
Star Forming ◽  
Star Forming Regions ◽  
Compact Region ◽  
Dense Cores ◽  
H Ii Region ◽  
Narrow Width ◽  
Water Masers ◽  
Small Clusters

Small clusters of recently-formed massive stars with their associated compact H II regions are often found embedded in the dense cores of molecular clouds. The H2CO opacity is correlated with the compactness of the H II region and is especially high for those with associated maser activity although additional factors are involved for the ultra-compact H II regions (UCH II). VLA observations of H2CO at 2 cm have been made towards the UCH II regions of W49-north. The highest H2CO opacity of 1.0 is found towards region A which does not have maser activity; yet one of the most compact region C, has an H2CO opacity of only 0.3, For these sources the integrated H2CO opacity (over the entire profile) may be more indicative of compactness. This may be due to the broader H2CO lines which can occur towards the maser regions. For example, large line widths of 10 to 12 km s−1 ate found towards W49-north G where the most intense water masers are located and towards W49-north B which has OH masers. The H2CO line with the highest 2 cm opacity of 2.5 and a narrow width of 2 km s−1 is found towards the UCH II region ON 3 which has only weak H2O maser emission.

scholarly journals The excitation of OH by H2 revisited – II. Hyperfine resolved rate coefficients

2020 ◽  
Vol 493 (3) ◽  
pp. 3491-3495 ◽  
Author(s):  
J Kłos ◽  
P J Dagdigian ◽  
M H Alexander ◽  
A Faure ◽  
F Lique
Keyword(s):  
Molecular Clouds ◽  
Emission Spectra ◽  
Rate Coefficients ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Wide Range ◽  
State Rate ◽  
Collisional Rate Coefficients ◽  
Collisional Rate

ABSTRACT Observations of hyperfine resolved transitions of the hydroxyl radical (OH) are unique probes of the physical conditions in molecular clouds. In particular, hyperfine intensities can be used as an effective thermometer over a wide range of molecular densities. Accurate modelling of the OH emission spectra requires the calculation of collisional rate coefficients for the excitation of OH by H2, the most abundant collisional partner in the molecular clouds. Here, we determine hyperfine resolved rate coefficients for the excitation of OH by H2 using a recently developed highly accurate potential energy surface. State-to-state rate coefficients between the lower hyperfine levels were calculated using recoupling techniques for temperature ranging from 10 to 150 K. Significant differences were found with the earlier values currently used in astrophysical models, the new rate coefficients being larger than the previous ones. Finally, we compute the excitation of the OH radical in cold molecular clouds and star-forming regions. The new rate coefficients were found to increase the hyperfine intensities by a factor of ∼1–2. Consequently, we recommend using this new set of data in any astrophysical model of OH excitation.

scholarly journals Clues on Arp 142: The spiral–elliptical merger

2019 ◽  
Vol 488 (1) ◽  
pp. 830-846
Author(s):  
Marcelo D Mora ◽  
Sergio Torres-Flores ◽  
Verónica Firpo ◽  
Jose A Hernandez-Jimenez ◽  
Fernanda Urrutia-Viscarra ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Morphological Characteristics ◽  
Current Data ◽  
Ionization Mechanism ◽  
H Ii Regions ◽  
Data Set ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Individual

Abstract Nearby merging pairs are unique laboratories in which one can study the gravitational effects on the individual interacting components. In this manuscript, we report the characterization of selected H ii regions along the peculiar galaxy NGC 2936, member of the galaxy pair Arp 142, an E+S interaction, known as ‘The Penguin’. Using Gemini South spectroscopy, we have derived a high enhancement of the global star formation rate (SFR) = 35.9 M⊙ yr−1 probably stimulated by the interaction. Star-forming regions on this galaxy display oxygen abundances that are consistent with solar metallicities. The current data set does not allow us to conclude any clear scenario for NGC 2936. Diagnostic diagrams suggest that the central region of NGC 2936 is ionized by active galactic nucleus (AGN) activity and the eastern tidal plume in NGC 2936 is experiencing a burst of star formation, which may be triggered by the gas compression due to the interaction event with its elliptical companion galaxy: NGC 2937. The ionization mechanism of these sources is consistent with shock models of low velocities of 200–300 km s −1. The isophotal analysis shows tidal features on NGC 2937: at inner radii non-concentric (or off-centring) isophotes, and at large radii, a faint excess of the surface brightness profile with respect to de Vaucouleurs law. By comparing the radial velocity profiles and morphological characteristics of Arp 142 with a library of numerical simulations, we conclude that the current stage of the system would be about 50 ± 25 Myr after the first pericentre passage.

scholarly journals Structure and expansion law of H ii regions in structured molecular clouds

2019 ◽  
Vol 487 (2) ◽  
pp. 2200-2214 ◽  
Author(s):  
Manuel Zamora-Avilés ◽  
Enrique Vázquez-Semadeni ◽  
Ricardo F González ◽  
José Franco ◽  
Steven N Shore ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Massive Star ◽  
Mean Value ◽  
Neutral Medium ◽  
H Ii Regions ◽  
Star Forming ◽  
Star Forming Regions ◽  
H Ii Region ◽  
Analytical Result ◽  
Magnetohydrodynamic Simulations

Abstract We present radiation-magnetohydrodynamic simulations aimed at studying evolutionary properties of H ii regions in turbulent, magnetized, and collapsing molecular clouds formed by converging flows in the warm neutral medium. We focus on the structure, dynamics, and expansion laws of these regions. Once a massive star forms in our highly structured clouds, its ionizing radiation eventually stops the accretion (through filaments) towards the massive star-forming regions. The new overpressured H ii regions push away the dense gas, thus disrupting the more massive collapse centres. Also, because of the complex density structure in the cloud, the H ii regions expand in a hybrid manner: they virtually do not expand towards the densest regions (cores), while they expand according to the classical analytical result towards the rest of the cloud, and in an accelerated way, as a blister region, towards the diffuse medium. Thus, the ionized regions grow anisotropically, and the ionizing stars generally appear off-centre of the regions. Finally, we find that the hypotheses assumed in standard H ii-region expansion models (fully embedded region, blister-type, or expansion in a density gradient) apply simultaneously in different parts of our simulated H ii regions, producing a net expansion law (R∝ tα, with α in the range of 0.93–1.47 and a mean value of 1.2 ± 0.17) that differs from any of those of the standard models.

scholarly journals Masers in Star Forming Regions

1987 ◽  
Vol 115 ◽  
pp. 333-334 ◽  
Author(s):  
R. J. Cohen
Keyword(s):  
Young Stars ◽  
The Other ◽  
Circumstellar Disk ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Star Forming ◽  
Molecular Outflows ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Cepheus A

OH and H2O masers in star forming regions are important because they are readily detectable indicators of star formation and because they provide unique information on the kinematics and physical conditions in high density regions (106 – 1010 cm−3) surrounding young stars, regions which cannot be studied by other means at present. The Jodrell Bank MERLIN interferometer has been used to map a sample of OH and H2O masers associated with bipolar molecular outflows. The maps of Cepheus A show that the masers are closely associated with the densest compact H II regions at the centre of the flow. The masers appear to be located at the inner edges of the circumstellar disk thought to play a role in collimating the outflow. It is suggested that the H2O masers trace the interaction between the stellar wind and the dense molecular gas, and the OH masers trace shocks propagating into the molecular gas. Rapid and sometimes correlated variations in the maser emission suggest that radiative pumping is likely in this source (Rowland and Cohen, Mon. Not. R. Astr. Soc. in press). Study of the other sources is still in progress.

scholarly journals Properties of nearby giant star-forming regions

1999 ◽  
Vol 193 ◽  
pp. 418-428
Author(s):  
Deidre A. Hunter
Keyword(s):  
Star Formation ◽  
Stellar Populations ◽  
Young Star ◽  
Gas Content ◽  
H Ii Regions ◽  
Giant Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
H Ii Region ◽  
30 Doradus

I review the properties of two nearby giant H II regions — 30 Doradus and NGC 604, and of two nearby young star complexes now past the H II region phase — Constellation III and NGC 206. I discuss the stellar populations, mode of star formation, gas content, and kinematics as clues to what conditions may be like in more distant starburst environments.

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.

Sign in / Sign up

Export Citation Format

Share Document