scholarly journals Molecular environments of the supernova remnant G359.1−0.5

2020 ◽  
Vol 493 (3) ◽  
pp. 3947-3955 ◽  
Author(s):  
L K Eppens ◽  
E M Reynoso ◽  
J Lazendic-Galloway ◽  
J A Combi ◽  
J F Albacete-Colombo
Keyword(s):  
Molecular Structure ◽  
Supernova Remnant ◽  
Molecular Study ◽  
Molecular Gas ◽  
Molecular Line ◽  
Γ Rays ◽  
Γ Ray ◽  
Co Emission ◽  
Co Observations ◽  
Morphological Correlation

ABSTRACT We report new CO observations and a detailed molecular-line study of the mixed morphology supernova remnant G359.1−0.5, which contains six OH (1720 MHz) masers along the radio shell, indicative of shock-cloud interaction. Observations of 12CO and 13CO J:1–0 lines were performed in a ∼38 × 38 arcmin area with the on-the-fly technique using the Kit Peak 12 Meter telescope. The molecular study has revealed the existence of a few clumps with densities ∼103 cm−3 compatible in velocity and position with the OH (1720 MHz) masers. These clumps, in turn, appear to be part of a larger, elongated molecular structure ∼34 arcmin long extending between −12.48 and +1.83 km s−1, adjacent to the western edge of the radio shell. According to the densities and relative position with respect to the masers, we conclude that the CO clouds depict unshocked gas, as observed in other remnants with OH (1720 MHz) masers. In addition, we investigated the distribution of the molecular gas towards the adjacent γ-ray source HESS J1745-303 (Aharonian et al. 2006) but could not find any morphological correlation between the γ-rays and the CO emission at any velocity in this region.

scholarly journals Wide-Line Molecular Clouds and the Gamma-Ray Deficit Toward the Galactic Center

1989 ◽  
Vol 136 ◽  
pp. 157-158 ◽  
Author(s):  
J. G. Stacy ◽  
M. E. Bitran ◽  
T. M. Dame ◽  
P. Thaddeus
Keyword(s):  
Gravitational Field ◽  
Molecular Clouds ◽  
Stellar Population ◽  
Gamma Ray ◽  
Galactic Center ◽  
Molecular Gas ◽  
Show Evidence ◽  
Wide Line ◽  
Γ Ray ◽  
Co Emission

The discrepancy between observed and predicted γ-ray emission toward the Galactic Center is attributed to a unique population of wide-line molecular clouds. The most prominent objects of this class show evidence of rotation and a significant stellar population. The observed 12CO emission traces the gravitational field produced primarily by stars, not molecular gas.

scholarly journals Constraints on high-J CO emission lines in z ∼ 6 quasars

2019 ◽  
Author(s):  
S Carniani ◽  
S Gallerani ◽  
L Vallini ◽  
A Pallottini ◽  
M Tazzari ◽  
...  
Keyword(s):  
Black Body ◽  
Continuum Emission ◽  
Molecular Gas ◽  
X Ray ◽  
Compact Region ◽  
Upper Limits ◽  
Gas Heating ◽  
Co Emission ◽  
Co Observations ◽  
The Continuum

Abstract We present Atacama Large Millimiter/submillimiter Array (ALMA) observations of eight highly excited CO (${\rm J_{\rm up}}$ >8) lines and continuum emission in two z ∼ 6 quasars: SDSS J231038.88+185519.7 (hereafter J2310), for which CO(8-7), CO(9-8), and CO(17-16) lines have been observed, and ULAS J131911.29+095951.4 (J1319), observed in the CO(14-13), CO(17-16) and CO(19-18) lines. The continuum emission of both quasars arises from a compact region (<0.9 kpc). By assuming a modified black-body law, we estimate dust masses of Log(Mdust/M⊙) = 8.75 ± 0.07 and Log(Mdust/M⊙) = 8.8 ± 0.2 and dust temperatures of Tdust = 76 ± 3 K and $T_{\rm dust}=66^{+15}_{-10}~{\rm K}$, respectively for J2310 and J1319. Only CO(8-7) and CO(9-8) in J2310 are detected, while 3σ upper limits on luminosities are reported for the other lines of both quasars. The CO line luminosities and upper limits measured in J2310 and J1319 are consistent with those observed in local AGN and starburst galaxies, and other z ∼ 6 quasars, except for SDSS J1148+5251 (J1148), the only quasar at z = 6.4 with a previous CO(17-16) line detection. By computing the CO SLEDs normalised to the CO(6-5) line and FIR luminosities for J2310, J1319, and J1149, we conclude that different gas heating mechanisms (X-ray radiation and/or shocks) may explain the different CO luminosities observed in these z ∼ 6 quasar. Future ${\rm J_{\rm up}}$ >8 CO observations will be crucial to understand the processes responsible for molecular gas excitation in luminous high-z quasars.

Can Galactic γ-Ray Background be due to Superposition of γ-Rays from Millisecond Pulsars?

1998 ◽  
Vol 188 ◽  
pp. 273-274
Author(s):  
V.B. Bhatia ◽  
S. Mishra ◽  
N. Panchapakesan
Keyword(s):  
Cosmic Rays ◽  
Cosmic Ray ◽  
Diffuse Radiation ◽  
High Energy ◽  
Molecular Gas ◽  
Inverse Compton Scattering ◽  
High Energy Electrons ◽  
Inverse Compton ◽  
Γ Rays ◽  
Γ Ray

The SAS 2 and COS B observations have established the existence of diffuse γ-rays in our Galaxy in various energy ranges. The diffuse radiation is attributed to the interaction of cosmic ray nuclei and electrons with the particles of interstellar atomic and molecular gas (via the decay of pions and bremsstrahlung, respectively). Inverse Compton scattering of interstellar photons by the high energy electrons of cosmic rays may also be contributing to this background. In addition some contribution may come from discrete sources of γ-rays.

scholarly journals Radio study of the extended TeV source VER J1907+062

2019 ◽  
Vol 491 (4) ◽  
pp. 5732-5739
Author(s):  
L Duvidovich ◽  
A Petriella ◽  
E Giacani
Keyword(s):  
Atomic Hydrogen ◽  
Molecular Clouds ◽  
Supernova Remnant ◽  
Molecular Gas ◽  
Radio Observations ◽  
Very Large Array ◽  
X Ray ◽  
New Radio ◽  
Γ Ray ◽  
Pulsar Wind

ABSTRACT This paper aims to provide new insights on the origin of the TeV source VER J1907+062 through new high-quality radio observations. We used the Karl G. Jansky Very Large Array (VLA) to observe the whole extension of VER J1907+062 at 1.5 GHz with a mosaicking technique and the PSR J1907+0602 in a single pointing at 6 GHz. These data were used together with 12CO and atomic hydrogen observations obtained from public surveys to investigate the interstellar medium in the direction of VER J1907+062. The new radio observations do not show any evidence of a pulsar wind nebula (PWN) driven by the pulsars present in the field and no radio counterpart to the proposed X-ray PWN powered by PSR J1907+0602 is seen in the new VLA image at 6 GHz down to a noise level of 10 $\mu$Jy beam−1. Molecular clouds were discovered over the eastern, southern, and western borders of the radio shell of G40.5−0.5, suggesting an association with this supernova remnant. We explored several scenarios for the origin of VER J1907+062. We propose as the most probable scenario one in which the TeV emission is produced by two separated γ-ray sources located at different distances: one of leptonic origin and associated with a PWN powered by PSR J1907+0602 at ∼3.2 kpc and another of hadronic origin and produced by the interaction between G40.5−0.5 and the surrounding molecular gas at ∼8.7 kpc.

scholarly journals CO Observations of Bright IRAS Galaxies

1987 ◽  
Vol 115 ◽  
pp. 653-653
Author(s):  
D. B. Sanders
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Formation Rate ◽  
Far Infrared ◽  
Molecular Gas ◽  
Infrared Excess ◽  
Luminous Galaxies ◽  
Be Star ◽  
Co Emission ◽  
Co Observations

CO emission has been detected from 75 bright infrared galaxies with CZ = 2 000 – 16 000 km/s. These include the most distant and the most luminous galaxies (Arp 55, IR 1713+63) yet detected in CO. All of these galaxies are rich in molecular gas with Mtotal (H2) = 2 × 109 −6x1010 M⊙, and they have a strong far-infrared excess, with LFIR/LB = 2-40 and LFIR (40-400μ) = 1010 – 3 × 1012 L⊙. The primary luminosity source appears to be star formation in molecular clouds. A strong correlation is found between the FIR and 21-cm continuum flux, implying that the IMF is independent of the star formation rate. The ratio LFIR/M(H2) provides a measure of the current rate of star-formation, which is found to be a factor 3-20 larger in these galaxies than for the ensemble of molecular clouds in the Milky Way. VLA maps plus a few high resolution (14″-30″) CO (1-0) and CO (2-1) maps suggest that most of the luminosity comes from core regions 1-3 kpc in size. The abnormal concentration of molecular gas in these galactic cores is presumably the result of a collision or strong interaction with a nearby companion.

scholarly journals Tracing the cold molecular gas reservoir through dust emission in the SMC

2008 ◽  
Vol 4 (S256) ◽  
pp. 148-153
Author(s):  
Caroline Bot ◽  
Mónica Rubio ◽  
François Boulanger ◽  
Marcus Albrecht ◽  
Frank Bertoldi ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Virial Theorem ◽  
Spectral Energy Distribution ◽  
Dust Emission ◽  
Spectral Energy ◽  
Molecular Gas ◽  
Giant Molecular Clouds ◽  
Gas Reservoir ◽  
Co Emission ◽  
Co Observations

AbstractThe amount of molecular gas is a key for understanding the future star formation in a galaxy. However, this quantity is difficult to infer as the cold H2 is almost impossible to observe and, especially at low metallicities, CO only traces part of the clouds, keeping large envelopes of H2 hidden from observations. In this context, millimeter dust emission tracing the cold and dense regions can be used as a tracer to unveil the total molecular gas masses. I present studies of a sample of giant molecular clouds in the Small Magellanic Cloud. These clouds have been observed in the millimeter and sub-millimeter continuum of dust emission: with SIMBA/SEST at 1.2 mm and the new LABOCA bolometer on APEX at 870 μm. Combining these with radio data for each cloud, the spectral energy distribution of dust emission are obtained and gas masses are inferred. The molecular cloud masses are found to be systematically larger than the virial masses deduced from CO emission. Therefore, the molecular gas mass in the SMC has been underestimated by CO observations, even through the dynamical masses. This result confirms what was previously observed by Bot et al. (2007). We discuss possible interpretations of the mass discrepancy observed: in the giant molecular clouds of the SMC, part of cloud's support against gravity could be given by a magnetic field. Alternatively, the inclusion of surface terms in the virial theorem for turbulent clouds could reproduce the observed results and the giant molecular clouds could be transient structures.

scholarly journals CO Observations of the Central Bar of M83

1987 ◽  
Vol 115 ◽  
pp. 628-630 ◽  
Author(s):  
T. Handa ◽  
Y. Sofue ◽  
N. Nakai ◽  
M. Fujimoto ◽  
M. Hayashi
Keyword(s):  
Star Formation ◽  
Theoretical Model ◽  
Velocity Field ◽  
Spiral Galaxies ◽  
Raw Material ◽  
Molecular Gas ◽  
Nuclear Region ◽  
Barred Spiral Galaxies ◽  
Co Emission ◽  
Co Observations

CO observations of the nuclear region of the SABc galaxy M83 have been made with the 45-m telescope at NRO. A bar-like elongation of the CO emission along the optical bar and a velocity field which suggests noncircular motions are found. These results are consistent with predictions based on the theoretical model of barred spiral galaxies. The inflow and concentration of molecular gas in the nucleus of M83 may supply raw material which maintains a burst of star formation there.

scholarly journals The molecular gas mass of M 33

2017 ◽  
Vol 600 ◽  
pp. A27 ◽  
Author(s):  
P. Gratier ◽  
J. Braine ◽  
K. Schuster ◽  
E. Rosolowsky ◽  
M. Boquien ◽  
...  
Keyword(s):  
Large Population ◽  
Density Ratio ◽  
Dust Emission ◽  
Molecular Gas ◽  
Galactocentric Distance ◽  
Large Program ◽  
Low Metallicity ◽  
Dust Surface ◽  
Co Emission ◽  
Co Observations

Do some environments favor efficient conversion of molecular gas into stars? To answer this, we need to be able to estimate the H2 mass. Traditionally, this is done using CO observations and a few assumptions but the Herschel observations which cover the far-IR dust spectrum make it possible to estimate the molecular gas mass independently of CO and thus to investigate whether and how the CO traces H2. Previous attempts to derive gas masses from dust emission suffered from biases. Generally, dust surface densities, H i column densities, and CO intensities are used to derive a gas-to-dust ratio (GDR) and the local CO intensity to H2 column density ratio (XCO), sometimes allowing for an additional CO-dark gas component (Kdark). We tested earlier methods, revealing degeneracies among the parameters, and then used a sophisticated Bayesian formalism to derive the most likely values for each of the parameters mentioned above as a function of position in the nearby prototypical low metallicity (12 + log (O/H) ~ 8.4) spiral galaxy M 33. The data are from the IRAM Large Program mapping in the CO(2–1) line along with high-resolution H i and Herschel dust continuum observations. Solving for GDR, XCO, and Kdark in macropixels 500 pc in size, each containing many individual measurements of the CO, H i, and dust emission, we find that (i) allowing for CO dark gas (Kdark) significantly improves fits; (ii) Kdark decreases with galactocentric distance; (iii) GDR is slightly higher than initially expected and increases with galactocentric distance; (iv) the total amount of dark gas closely follows the radially decreasing CO emission, as might be expected if the dark gas is H2 where CO is photodissociated. The total amount of H2, including dark gas, yields an average XCO of twice the galactic value of 2 × 1020 cm-2/ K km s-1, with about 55% of this traced directly through CO. The rather constant fraction of dark gas suggests that there is no large population of diffuse H2 clouds (unrelated to GMCs) without CO emission. Unlike in large spirals, we detect no systematic radial trend in XCO, possibly linked to the absence of a radial decrease in CO line ratios.

scholarly journals An Atomic and Molecular Study of the Interstellar Medium Around the Supernova Remnant RCW 103

2006 ◽  
Vol 23 (2) ◽  
pp. 69-75 ◽  
Author(s):  
Sergio A. Paron ◽  
Estela M. Reynoso ◽  
Cormac Purcell ◽  
Gloria M. Dubner ◽  
Anne Green
Keyword(s):  
Interstellar Medium ◽  
Shock Front ◽  
Supernova Remnant ◽  
Molecular Study ◽  
Rotational Transition ◽  
Molecular Feature ◽  
Infrared Observations ◽  
Southern Border ◽  
Co Emission ◽  
Compact Array

AbstractWe report on the detection of HCO+ and 12CO emission in the rotational transition J = 1–0 in the vicinity of the shock front at the southern border of the supernova remnant RCW 103, where previous infrared observations suggest an interaction with a molecular cloud. The observations were carried out with the Australian Millimeter Radiotelescope at Mopra. We observed a depletion of HCO+ behind the supernova shock front. In addition, we studied the interstellar medium over an extended region towards RCW 103 based on archival λ 21 cm Hı line observations from the Australia Telescope Compact Array (ATCA) and the Parkes Telescope. No atomic gas was observed in emission in coincidence with the molecular feature. This absence was interpreted in terms of self-absorption processes.

scholarly journals Major impact from a minor merger

2018 ◽  
Vol 615 ◽  
pp. A122 ◽  
Author(s):  
S. König ◽  
S. Aalto ◽  
S. Muller ◽  
J. S. Gallagher III ◽  
R. J. Beswick ◽  
...  
Keyword(s):  
Star Formation ◽  
Brightness Temperature ◽  
Central Region ◽  
Molecular Clouds ◽  
Molecular Gas ◽  
Transfer Model ◽  
Dense Gas ◽  
Giant Molecular Clouds ◽  
Minor Mergers ◽  
Co Emission

Context. Minor mergers are important processes contributing significantly to how galaxies evolve across the age of the Universe. Their impact on the growth of supermassive black holes and star formation is profound – about half of the star formation activity in the local Universe is the result of minor mergers. Aims. The detailed study of dense molecular gas in galaxies provides an important test of the validity of the relation between star formation rate and HCN luminosity on different galactic scales – from whole galaxies to giant molecular clouds in their molecular gas-rich centers. Methods. We use observations of HCN and HCO+ 1−0 with NOEMA and of CO3−2 with the SMA to study the properties of the dense molecular gas in the Medusa merger (NGC 4194) at 1′′ resolution. In particular, we compare the distribution of these dense gas tracers with CO2−1 high-resolution maps in the Medusa merger. To characterize gas properties, we calculate the brightness temperature ratios between the three tracers and use them in conjunction with a non-local thermodynamic equilibrium (non-LTE) radiative line transfer model. Results. The gas represented by HCN and HCO+ 1−0, and CO3−2 does not occupy the same structures as the less dense gas associated with the lower-J CO emission. Interestingly, the only emission from dense gas is detected in a 200 pc region within the “Eye of the Medusa”, an asymmetric 500 pc off-nuclear concentration of molecular gas. Surprisingly, no HCN or HCO+ is detected for the extended starburst of the Medusa merger. Additionally, there are only small amounts of HCN or HCO+ associated with the active galactic nucleus. The CO3−2/2−1 brightness temperature ratio inside “the Eye” is ~2.5 – the highest ratio found so far – implying optically thin CO emission. The CO2−1/HCN 1−0 (~9.8) and CO2−1/HCO+ 1−0 (~7.9) ratios show that the dense gas filling factor must be relatively high in the central region, consistent with the elevated CO3−1/2−1 ratio. Conclusions. The line ratios reveal an extreme, fragmented molecular cloud population inside the Eye with large bulk temperatures (T > 300 K) and high gas densities (n(H2) > 104 cm-3). This is very different from the cool, self-gravitating structures of giant molecular clouds normally found in the disks of galaxies. The Eye of the Medusa is found at an interface between a large-scale minor axis inflow and the central region of the Medusa. Hence, the extreme conditions inside the Eye may be the result of the radiative and mechanical feedback from a deeply embedded, young and massive super star cluster formed due to the gas pile-up at the intersection. Alternatively, shocks from the inflowing gas entering the central region of the Medusa may be strong enough to shock and fragment the gas. For both scenarios, however, it appears that the HCN and HCO+ dense gas tracers are not probing star formation, but instead a post-starburst and/or shocked ISM that is too hot and fragmented to form newstars. Thus, caution is advised in taking the detection of emission from dense gas tracers as evidence of ongoing or imminent star formation.

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