scholarly journals ASTE CO(3-2) observations of M 83: Correlation between CO(3-2)/CO(1-0) ratios and star formation efficiencies

2006 ◽  
Vol 2 (S237) ◽  
pp. 451-451
Author(s):  
K. Muraoka ◽  
K. Kohno ◽  
T. Tosaki ◽  
N. Kuno ◽  
K. Nakanishi ◽  
...  
Keyword(s):  
Star Formation ◽  
Spatial Variation ◽  
Radial Profile ◽  
Radio Continuum ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Integrated Intensity ◽  
Barred Spiral Galaxy ◽  
Simple Summation

AbstractWe have performed CO(J=3−2) emission observations with the Atacama Submillimeter Telescope Experiment (ASTE) toward the 5′ × 5′ (or 6.6 × 6.6 kpc at the distance D = 4.5 Mpc) region of the nearby barred spiral galaxy M 83. We successfully resolved the major structures, i.e., the nuclear starburst region, bar, and inner spiral arms in CO(J=3−2) emission at a resolution of 22'' (or 480 pc), showing a good spatial coincidence between CO(J=3−2) and 6 cm continuum emissions.From a comparison of CO(J=3−2) data with CO(J=1−0) intensities measured with Nobeyama 45-m telescope, we found that the radial profile of CO(J=3−2)/CO(J=1−0) integrated intensity ratio R3−2/1−0 is almost unity in the central region (r<0.25 kpc), whereas it drops to a constant value, 0.6–0.7, in the disk region. The radial profile of star formation efficiencies (SFEs), determined from 6 cm radio continuum and CO(J=1−0) emission, shows the same trend as that of R3−2/1−0. At the bar-end (r ~ 2.4 kpc), the amounts of molecular gas and the massive stars are enhanced when compared with other disk regions, whereas there is no excess of R3−2/1−0 and SFE in that region. This means that a simple summation of the star forming regions at the bar-end and the disk cannot reproduce the nuclear starburst of M 83, implying that the spatial variation of the dense gas fraction traced by R3−2/1−0 governs the spatial variation of SFE in M 83.

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 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 Star Formation in the Large Magellanic Cloud

1987 ◽  
Vol 115 ◽  
pp. 521-533
Author(s):  
J. V. Feitzinger
Keyword(s):  
Star Formation ◽  
Large Magellanic Cloud ◽  
Radio Continuum ◽  
Physical Parameters ◽  
Formation Processes ◽  
Star Forming ◽  
Star Forming Regions ◽  
Scale Structures ◽  
And Cluster Analysis ◽  
Spiral Arm

Methods used in pattern recognition and cluster analysis are applied to investigate the spatial distribution of the star forming regions. The fractal dimension of these structures is deduced. The new 21 cm, radio continuum (1.4 GHz) and IRAS surveys reveal scale structures of 700 pc to 1500 pc being identical with the optically identified star forming sites. The morphological structures delineated by young stars reflect physical parameters which determine the star formation in this galaxy. The formation of spiral arm filaments is understandable by stochastic selfpropagating star formation processes.

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 Star-Forming Regions in the SMC

2006 ◽  
Vol 2 (S235) ◽  
pp. 311-311
Author(s):  
I. Gonidakis ◽  
E. Livanou ◽  
E. Kontizas ◽  
U. Klein ◽  
M. Kontizas ◽  
...  
Keyword(s):  
Star Formation ◽  
Starburst Galaxies ◽  
Radio Continuum ◽  
Spectral Energy ◽  
High Concentration ◽  
Star Forming ◽  
Star Forming Regions ◽  
The North ◽  
Star Formation Activity ◽  
West Part

AbstractSMC has been going through an active star formation epoch, especially during the last 0.2 Gyr when the close encounter with the LMC occured. Our goal is to detect regions dominated by early-type stars and gas and examine their behaviour at different wavelengths. Spectral energy distributions, a colour-magnitude diagram and a two-colour diagram from IRAS data (Bontekoe, Koperet & Kester (1994); Bontekoe, Kester, Stanimirović, et al. (1999)) for these regions were used in order to compare their properties with those of starburst galaxies (Helou (1986); Lehnert & Heckman (1995)). We have selected 50 stellar complexes with increased 100-μm IRAS flux, with detetected emission in all IRAS bands and/or high concentration of young stars. Ranking them by size (Maragoudaki, Kontizas, Kontizas, et al. (1998)), a total of what we call 24 aggregates, 23 complexes and 3 super-complexes were found. Radio continuum maps at 8.6-GHz (Haynes, Murray, Klein, et al. (1986)) and the CO (1→0) line (Mizuno, Rubio, Mizuno, et al. (2001)) were also correlated with the map of the complexes. Only 8 of them show enhanced star formation activity according to their IR properties and 8.6-GHz map, however, none of them resembles the IR behaviour of starburst regions found in the LMC and starburst galaxies (Livanou, Kontizas, Gonidakis, et al. (2006)). The south-west part of the “bar” has the most diverse intensity of star formation, with CO emission coincident with the largest structure. In the north-eastern end of the “bar”, star formation is likely to have commenced in the recent past, with molecular gas being abundant in this region. Ongoing and future star formation are revealed in the wing, while it appears to have ceased in the central “bar”.

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.

Numerical Modelling of Star Formation in GMCs

1992 ◽  
Vol 10 (2) ◽  
pp. 122-124
Author(s):  
John C. Lattanzio ◽  
J.J. Monaghan
Keyword(s):  
Star Formation ◽  
Numerical Modelling ◽  
Formation Process ◽  
Fragmentation Process ◽  
Molecular Gas ◽  
Preliminary Calculation ◽  
Star Forming ◽  
Star Forming Regions ◽  
Complex Process ◽  
Spherical Models

AbstractAlthough stars can be approximated very satisfactorily by spherical models, it is clear from observations of star forming regions that the break-up of molecular gas to form proto-stars is a highly complex process that cannot be approximated simply. As a consequence, the theoretical picture of fragmentation, which is based on assuming that fragmentation occurs in uniform, static, isothermal clouds, is too crude to provide a guide to the star formation process. The alternative is to simulate the fragmentation process numerically with the ultimate aim of evolving the gas to proto-stars. The difficulties involved with this procedure are discussed in this paper. We also discuss our proposed solution to this problem, together with a very preliminary calculation.

scholarly journals Star Formation in the Local Milky Way

2015 ◽  
Vol 10 (S314) ◽  
pp. 8-15
Author(s):  
Charles J. Lada
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Milky Way ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Young Stars ◽  
Molecular Gas ◽  
Physical Processes ◽  
Star Forming ◽  
Star Forming Regions

AbstractStudies of molecular clouds and young stars near the sun have provided invaluable insights into the process of star formation. Indeed, much of our physical understanding of this topic has been derived from such studies. Perhaps the two most fundamental problems confronting star formation research today are: 1) determining the origin of stellar mass and 2) deciphering the nature of the physical processes that control the star formation rate in molecular gas. As I will briefly outline here, observations and studies of local star forming regions are making particularly significant contributions toward the solution of both these important problems.

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 VLT/MUSE and ATCA Observations of the Host Galaxy of the Short GRB 080905A at z = 0.122

2021 ◽  
Vol 923 (1) ◽  
pp. 38
Author(s):  
A. M. Nicuesa Guelbenzu ◽  
S. Klose ◽  
P. Schady ◽  
K. Belczynski ◽  
D. H. Hartmann ◽  
...  
Keyword(s):  
Star Formation ◽  
Line Emission ◽  
Large Magellanic Cloud ◽  
Radio Continuum ◽  
Host Galaxy ◽  
Strong Line ◽  
Host Galaxies ◽  
Star Forming ◽  
Star Forming Regions ◽  
Field Unit

Abstract Short-GRB progenitors could come in various flavors, depending on the nature of the merging compact stellar objects (including a stellar-mass black hole or not) or depending on their ages (millions or billions of years). At a redshift of z = 0.122, the nearly face-on spiral host of the short GRB 080905A is one of the closest short-GRB host galaxies identified so far. This made it a preferred target to explore spatially resolved star formation and to investigate the afterglow position in the context of its star formation structures. We used VLT/MUSE integral-field unit observations, supplemented by ATCA 5.5/9.0 GHz radio-continuum measurements and publicly available HST data, to study the star formation activity in the GRB 080905A host galaxy. The MUSE observations reveal that the entire host is characterized by strong line emission. Using the Hα line flux, we measure for the entire galaxy an SFR of about 1.6 M ⊙ yr−1, consistent with its non-detection by ATCA. Several individual star-forming regions are scattered across the host. The most luminous region has a Hα luminosity that is nearly four times as high as the luminosity of the Tarantula nebula in the Large Magellanic Cloud. Even though star-forming activity can be traced as close to about 3 kpc (in projection) distance to the GRB explosion site, stellar population synthesis calculations show that none of the Hα-bright star-forming regions is a likely birthplace of the short-GRB progenitor.

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