scholarly journals Resolved spectral variations of the centimetre-wavelength continuum from the ρ Oph W photo-dissociation-region

2021 ◽  
Author(s):  
Simon Casassus ◽  
Matías Vidal ◽  
Carla Arce-Tord ◽  
Clive Dickinson ◽  
Glenn J White ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Dust Emission ◽  
Image Synthesis ◽  
Microwave Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Parametric Image ◽  
Physical Conditions ◽  
Morphological Differences ◽  
Dust Grain

Abstract Cm-wavelength radio continuum emission in excess of free-free, synchrotron and Rayleigh-Jeans dust emission (excess microwave emission, EME), and often called ‘anomalous microwave emission’, is bright in molecular cloud regions exposed to UV radiation, i.e. in photo-dissociation regions (PDRs). The EME correlates with IR dust emission on degree angular scales. Resolved observations of well-studied PDRs are needed to compare the spectral variations of the cm-continuum with tracers of physical conditions and of the dust grain population. The EME is particularly bright in the regions of the ρ Ophiuchi molecular cloud (ρ Oph) that surround the earliest type star in the complex, HD 147889, where the peak signal stems from the filament known as the ρ Oph-W PDR. Here we report on ATCA observations of ρ Oph-W that resolve the width of the filament. We recover extended emission using a variant of non-parametric image synthesis performed in the sky plane. The multi-frequency 17 GHz to 39 GHz mosaics reveal spectral variations in the cm-wavelength continuum. At ∼30 arcsec resolutions, the 17-20 GHz intensities follow tightly the mid-IR, Icm∝I(8 μm), despite the breakdown of this correlation on larger scales. However, while the 33-39 GHz filament is parallel to IRAC 8 μm, it is offset by 15–20 arcsec towards the UV source. Such morphological differences in frequency reflect spectral variations, which we quantify spectroscopically as a sharp and steepening high-frequency cutoff, interpreted in terms of the spinning dust emission mechanism as a minimum grain size acutoff ∼ 6 ± 1 Å that increases deeper into the PDR.

The diagnostic power of radio spectra from star-forming galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 177-186
Author(s):  
Eric J. Murphy
Keyword(s):  
Star Formation ◽  
Dust Emission ◽  
Cosmic Ray ◽  
Microwave Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Synchrotron Emission ◽  
Very Large Array ◽  
Star Forming

AbstractRadio continuum emission from galaxies is powered by a combination of distinct physical processes, each providing unique diagnostic information. Over frequencies spanning ∼ 1–120 GHz, radio spectra of star-forming galaxies are primarily comprised of: (1) non-thermal synchrotron emission powered by accelerated cosmic-ray electrons/positrons; (2) free-free emission from young massive star-forming (H ii) regions; (3) anomalous microwave emission, which is a dominant, but completely unconstrained, foreground in cosmic microwave background experiments; and (4) cold, thermal dust emission that accounts for most of the dust and total mass content in the interstellar medium in galaxies. In this proceeding, we discuss these key energetic processes that contribute to the radio emission from star-forming galaxies, with an emphasis on frequencies ≳30 GHz, where current investigations of star formation within nearby galaxies show that the free-free emission begins to dominate over non-thermal synchrotron emission. We also discuss how planned radio facilities that will access these frequencies, such as a next-generation Very Large Array (ngVLA), will be transformative to our understanding of the star formation process in galaxies.

scholarly journals A Gas and Dust Rich Giant Elliptical Galaxy

2005 ◽  
Vol 13 ◽  
pp. 872-874
Author(s):  
O. Krause ◽  
U. Lisenfeld ◽  
U. Klaas ◽  
D. Lemke ◽  
M. Haas ◽  
...  
Keyword(s):  
Elliptical Galaxy ◽  
Dust Emission ◽  
Optical Spectra ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Bolometric Luminosity ◽  
Thermal Radio ◽  
Visual Extinction ◽  
Dust Mass ◽  
Ir Emission

AbstractThe bolometric luminosity of LFIR = 2×1012 L⊙ makes ISOSS J 15079+7247 one of the most luminous and unusual galaxies detected by the 170 μm ISOPHOT Serendipity Survey (ISOSS). The detection of CO (1-0) emission identifies a giant elliptical galaxy at redshift z = 0.2136 as the counterpart of the FIR source. The derived high gas mass of 3 × 1010 M⊙ favours the picture that the dust emission is associated with this elliptical galaxy. The ultraluminous IR emission can be explained by a hidden starburst in the center of the elliptical. This is supported by the strength of non-thermal radio continuum emission. The huge dust mass of 5×108 M⊙ corresponds to a visual extinction of AV ~ 1000 mag, being consistent with the non-detection of any signatures of a strong starburst in ISOSS J 15079+7247 in optical spectra.

scholarly journals Modelling the spinning dust emission from LDN 1780

2020 ◽  
Vol 495 (1) ◽  
pp. 1122-1135 ◽  
Author(s):  
Matias Vidal ◽  
Clive Dickinson ◽  
S E Harper ◽  
Simon Casassus ◽  
A N Witt
Keyword(s):  
Angular Resolution ◽  
Spectral Energy Distribution ◽  
Dust Emission ◽  
Microwave Emission ◽  
Spectral Energy ◽  
Frequency Range ◽  
Polycyclic Aromatic ◽  
The Difference ◽  
Dust Grain ◽  
Sd Model

ABSTRACT We study the anomalous microwave emission (AME) in the Lynds Dark Nebula (LDN) 1780 on two angular scales. With publicly available data at an angular resolution of 1°, we studied the spectral energy distribution of the cloud in the 0.408–2997 GHz frequency range. The cloud presents a significant (>20σ) amount of AME, making it one of the clearest examples of AME on 1 ° scales, and its spectrum can be well fitted with a spinning dust (SD) model. We also find at these angular scales that the location of the peak of the emission at lower frequencies (23–70 GHz) differs from the location at the higher frequencies (90–3000 GHz) maps. In addition to the analysis on 1° angular scales, we present data from the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at 31 GHz with an angular resolution of 2 arcmin, in order to study the origin of the AME in LDN 1780. We studied morphological correlations between the CARMA map and different infrared tracers of dust emission. We found that the best correlation is with the 70- μm template, which traces warm dust (T ∼ 50 K). Finally, we study the difference in radio emissivity between two locations within the cloud. We measured a factor of ≈6 difference in 31-GHz emissivity. We show that this variation can be explained, using the SD model, by a variation on the dust grain size distribution across the cloud, particularly changing the fraction of polycyclic aromatic hydrocarbon for a fixed total amount of carbon.

scholarly journals Dark Supernova Remnants Revealed by CO-Line Bubbles in the W43 Molecular Complex along the 4-kpc Galactic Arm

Galaxies ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 13
Author(s):  
Yoshiaki Sofue
Keyword(s):  
Molecular Clouds ◽  
Supernova Remnants ◽  
Dust Emission ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Giant Molecular Clouds ◽  
Turbulent Structures ◽  
Stellar Objects ◽  
Receiver System

Fine structure of the density distribution in giant molecular clouds (GMCs) around W43 (G31+00+90 km s−1at ∼5.5 kpc) was analyzed using the FUGIN* CO-line survey at high-angular (20”∼0.5 pc) and velocity (1.3 km s−1) resolutions (*Four-receiver-system Unbiased Galactic Imaging survey with the Nobeyama 45-m telescope). The GMCs show highly turbulent structures, and the eddies are found to exhibit spherical bubble morphology appearing in narrow ranges of velocity channels. The bubbles are dark in radio continuum emission, unlike usual supernova remnants (SNR) or HII regions, and in infrared dust emission, unlike molecular bubbles around young stellar objects. The CO bubbles are interpreted as due to fully evolved buried SNRs in molecular clouds after rapid exhaustion of the released energy in dense molecular clouds. Then, the CO bubbles may be a direct evidence for exciting and maintaining the turbulence in GMCs by SN origin. Search for CO bubbles as “dark SNRs” (dSNR) will have implication to estimate the supernova rate more accurately, and hence the star formation activity in the Milky Way.

scholarly journals SRAO CO Observation of Supernova Remnants in l = 70° to 190°

2013 ◽  
Vol 9 (S296) ◽  
pp. 183-187
Author(s):  
Il-Gyo Jeong ◽  
Bon-Chul Koo
Keyword(s):  
Hydrodynamic Model ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Supernova Remnants ◽  
Spatial Relation ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Astronomy Observatory ◽  
Western Half ◽  
Co Emission

AbstractWe present the results 12CO J = 1–0 line observations of eleven Galactic supernova remnants (SNRs) between l = 70° and 190° obtained using the Seoul Radio Astronomy Observatory (SRAO) 6-m radio telescope. We detected CO emission towards most of the remnants. In seven SNRs, molecular clouds show a good spatial relation with their radio morphology: G73.9+0.9, G84.2−0.8, G85.4+0.7, G85.9−0.6, G93.3+6.9 (DA530), 94.0+1.0 (3C 434.1), and G182.4+4.3. Two SNRs are particularly interesting. In G85.4+0.7, there is a filamentary molecular cloud aligned along the south-east boundary of the remnant. This cloud extends to the nearby Hii region G84.9+0.5. If the molecular cloud is associated with both the Hii region and the SNR, the distance to the SNR would be 5–7 kpc. In 3C 434.1, there is a large molecular cloud blocking the western half of the remnant where the radio continuum emission is faint. The cloud shows a very good spatial correlation with radio continuum features, which strongly suggests the physical association of the cloud with the SNR. This gives a distance of 3 kpc to the SNR. We performed 12CO J = 2–1 line observations of this cloud using Kölner Observatorium für Sub-Millimeter Astronomie (KOSMA) 3-m telescope and found a region where the 12CO J = 2–1/1–0 line ratio is high. We present a hydrodynamic model showing that 3C434.1 could have resulted from a SN explosion occurred just outside the boundary of a thin, molecular cloud.

scholarly journals Distribution of Non-Thermal Emission in Galaxies

1981 ◽  
Vol 94 ◽  
pp. 209-214 ◽  
Author(s):  
R. Sancisi ◽  
P.C. van der Kruit
Keyword(s):  
Spiral Galaxies ◽  
Angular Resolution ◽  
Thermal Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Good Sensitivity ◽  
Physical Conditions ◽  
Large Samples ◽  
First Time

The properties of the radio continuum emission from spiral galaxies have been reviewed by Van der Kruit and Allen (1976) and by Van der Kruit (1978). In more recent years the major developments in the understanding of the radio continuum properties and the underlying physical conditions of galaxies have come from a number of surveys of large samples of objects. Some of these surveys (e.g. Hummel, 1980a) have good sensitivity and sufficiently high angular resolution to allow for the first time a clear separation of central sources and disk emission and a study of the properties of these components in a large number of galaxies. As a consequence some results already found, suggested or only suspected in previous detailed investigations of a limited number of objects are put on a firmer basis or entirely new aspects are revealed.

scholarly journals Relationships between Galactic Radio Continuum and HαEmission

1998 ◽  
Vol 15 (1) ◽  
pp. 64-69 ◽  
Author(s):  
L. E. Cram ◽  
A. J. Green ◽  
D. C.-J. Bock
Keyword(s):  
Thermal Emission ◽  
Line Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Physical Conditions ◽  
Thermal Radio Emission ◽  
The Relationship ◽  
Galactic Object ◽  
Galactic Radio ◽  
Made In

AbstractRadio continuum emission due to thermal bremsstrahlung and optical Hαspectral line emission arise from processes involving similar atomic entities and physical conditions. The relationship between the flux density of the emission from the two processes is mainly a function of the electron temperature of the emitting region, modified by other factors such as the mode of radiation transfer in the hydrogen spectrum. On the other hand, radio continuum radiation due to non-thermal synchrotron emission is formed by species and processes not involved in thermal emission. As a consequence, differences between the observed radio continuum emission and Hαemission from cosmic sources can provide reliable information on a variety of important physical aspects of the sources, including the relative importance of thermal and non-thermal radio emission and the degree of optical obscuration. This paper reviews the theory of the formation of Hαand the radio continuum in the interstellar medium (ISM), discusses some of the factors that must be considered in comparing observations made in the two frequency regimes, and summarises the properties of some classes of galactic object that emit both optical and radio radiation.

The radio continuum emission from the Galaxy

1964 ◽  
Vol 20 ◽  
pp. 102-106 ◽  
Author(s):  
B. Y. Mills
Keyword(s):  
Large Scale ◽  
Galactic Structure ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Physical Conditions ◽  
Galactic System ◽  
The Galaxy

Study of the radio continuum emission from the Galaxy is of interest both from the viewpoint of the physics of the radiating processes and the light which these shed on physical conditions within the Galaxy, and also because the large-scale organization of the emitting regions gives information about the structure of the Galaxy as a whole. We are concerned here particularly with the latter aspect, that is, the question of galactic structure, and for this we need to know the distribution of the emitting regions throughout the Galactic System.

scholarly journals Self-scattering of non-spherical dust grains

2020 ◽  
Vol 638 ◽  
pp. A116 ◽  
Author(s):  
Florian Kirchschlager ◽  
Gesa H.-M. Bertrang
Keyword(s):  
Dust Emission ◽  
Dipole Approximation ◽  
Continuum Emission ◽  
Incoming Wave ◽  
Grain Sizes ◽  
Order Of Magnitude ◽  
Dust Grain ◽  
Spherical Grains ◽  
The Impact ◽  
Protoplanetary Discs

Context. The understanding of (sub-)millimetre polarisation has made a leap forward since high-resolution imaging with the Atacama Large (sub-)Mm Array (ALMA) became available. Amongst other effects, self-scattering (i.e. the scattering of thermal dust emission on other grains) is thought to be the origin of millimetre polarisation. This opens the first window to a direct measurement of dust grain sizes in regions of optically thick continuum emission as it can be found in protoplanetary discs and star-forming regions. However, the newly derived values of grain sizes are usually around ~100 μm and thus one order of magnitude smaller than those obtained from more indirect measurements, as well as those expected from theory (~1 mm). Aims. We see the origin of this contradiction in the applied dust model of current self-scattering simulations: a perfect compact sphere. The aim of this study is to test our hypothesis by investigating the impact of non-spherical grain shapes on the self-scattering signal. Methods. We applied discrete dipole approximation simulations to investigate the influence of the grain shape on self-scattering polarisation in three scenarios: an unpolarised and polarised incoming wave under a fixed and a varying incident polarisation angle. Results. We find significant deviations of the resulting self-scattering polarisation when comparing non-spherical to spherical grains. In particular, tremendous deviations are found for the polarisation signal of grains when observed outside the Rayleigh regime, that is for >100 μm sized grains observed at the 870 μm wavelength. Self-scattering by oblate grains produces higher polarisation degrees compared to spheres, which challenges the interpretation of the origin of observed millimetre polarisation. A (nearly) perfect alignment of the non-spherical grains is required to account for the observed millimetre polarisation in protoplanetary discs. Furthermore, we find conditions under which the emerging scattering polarisation of non-spherical grains is flipped in orientation by 90°. Conclusions. These results show clearly that the perfect compact sphere is an oversimplified model, which has reached its limit. Our findings point towards a necessary re-evaluation of the dust grain sizes derived from (sub-)millimetre polarisation.

scholarly journals The Orion Star-Forming Complex

1987 ◽  
Vol 115 ◽  
pp. 123-137 ◽  
Author(s):  
Tetsuo Hasegawa
Keyword(s):  
Dust Emission ◽  
Emission Feature ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Molecular Gas ◽  
Orion Nebula ◽  
Vibrationally Excited ◽  
Star Forming ◽  
H Ii Region ◽  
Co Emission

High resolution images of the Orion Nebula in the millimeter wave emission lines of CS and CO taken with the 45-m telescope at Nobeyama are presented. They cover a field approximately 400″ square with a 15″ – 34″ resolution and reveal a wealth of information on kinematic and density structures. The images of the J=1-0 (49 GHz) and J=2-1 (98 GHz) lines of CS show a long (>1 pc) and narrow (∼0.1 pc) N-S ridge of dense molecular gas. On the ridge, two major clumps are recognized; one is associated with the KL object and the other is 100″ south of it. The images of the J=1-0 (115 GHz) CO line indicate interaction between the molecular cloud and the H II region formed by the Trapezium stars. Bright CO emission is found towards the edges of the denser part of the H II region delineated by radio continuum emission. The CO emission coincides with the emission of vibrationally excited H2 and the 3.3 μm dust emission feature. The CO images reveal filamentary structures (“streamers”) stretching radially from the KL region. On the streamers there are Herbig-Haro objects moving away from the KL region. They may be tracers of weak interaction between the ambient molecular gas and mostly unseen, highly collimated, high-velocity (>200 km/s) jets.

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