Spatial distribution of far-infrared emission in spiral galaxies. I. Relation with radio continuum emission.

1997 ◽  
Vol 114 ◽  
pp. 932 ◽  
Author(s):  
Y. D. Mayya ◽  
T. N. Regaradjan
Keyword(s):  
Spatial Distribution ◽  
Spiral Galaxies ◽  
Far Infrared ◽  
Infrared Emission ◽  
Radio Continuum ◽  
Continuum Emission

scholarly journals Spatial Distribution of Far Infrared and Radio Continuum Emission in Spiral Galaxies

1996 ◽  
Vol 171 ◽  
pp. 415-415
Author(s):  
Y.D. Mayya ◽  
T.N. Rengarajan
Keyword(s):  
Spiral Galaxies ◽  
Far Infrared ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Emission Profile ◽  
Exponential Component ◽  
Dust Temperature ◽  
Order Of Magnitude ◽  
Disk Component ◽  
Exponential Disk

A study of 8 nearby spiral galaxies (NGC 2903, 3079, 3198, 3628, 4303, 4321, 4656 and 6946) is carried out using the radio continuum (RC) and far infrared (FIR) images at 1′ resolution. These images are used to study the radial gradients in the ratios of FIR to RC (Q60 and Q100), warm dust temperature (Td(60/100)) etc. The main results are illustrated with NGC 2903 as an example in Fig. 1, where azimuthally averaged quantities are plotted. Td(60/100) decreases away from the center (45–25 K), increasing again by ∼ 5 K in outer galaxies. Typically Q60 decreases by a factor of three away from the center in a given galaxy, but has an order of magnitude spread in the pixel values over all the galaxies. In contrast, Q100 shows flatter gradient, which is expected from the observed temperature gradient. 20 cm RC emission profile is also shown in Fig. 1. The RC and FIR profiles can be fitted by a combination of central gaussian and exponential disk components. In general RC and FIR have about the same fraction of exponential component with the exception of NGC 3628, in which the FIR is dominated by the gaussian while the RC is mostly disk component (see Fig. 2). In 5 of the remaining 7 galaxies, the exponential component contributes > 50% of the total. In general RC scale lengths are larger than the FIR.

scholarly journals Modeling the 60μm/20cm Infrared-to-Radio Ratio Within Spiral Galaxies

1990 ◽  
Vol 140 ◽  
pp. 237-238
Author(s):  
M. D. Bicay ◽  
G. Helou
Keyword(s):  
Spiral Galaxies ◽  
Far Infrared ◽  
Major Axis ◽  
Detailed Comparison ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Local Maxima ◽  
Central Regions ◽  
Order Of Magnitude ◽  
Nearby Galaxies

The remarkably tight global correlation between integrated far-infrared and radio continuum emission from spiral galaxies has recently stimulated interest in determining whether the relation holds spatially within galaxies (Wainscoat et al. 1987; Beck and Golla 1988; Bicay et al. 1989, hereafter Paper I). We report here on a detailed comparison of the distribution of 60μm infrared and 20cm radio continuum emission within 25 galaxies, mostly disk spirals. Local maxima in the thermal infrared and predominantly nonthermal radio maps are found to be spatially coincident on scales <0.3h−1 kpc in nearby galaxies. Superimposed on this broad correlation, we observe in the disks of most sample galaxies a slow decrease in the 60μm-to-20cm ratio Q60 with increasing radius. Values of Q60 within the central regions are often enhanced by a factor of 3 or more compared to the outer disks, whereas the corresponding enhancement in radio surface brightness is greater by at least an order of magnitude. The radial gradient in Q60 is most easily identified in nearby, face-on galaxies (e.g. NGC 5236, NGC 6946) due to the limited IRAS angular resolution. However, the gradient is also observed along the major axis of highly inclined systems (e.g. NGC 55).

scholarly journals Triggered high-mass star formation in the H ii region W 28 A2: A cloud–cloud collision scenario

2020 ◽  
Author(s):  
Katsuhiro Hayashi ◽  
Satoshi Yoshiike ◽  
Rei Enokiya ◽  
Shinji Fujita ◽  
Rin Yamada ◽  
...  
Keyword(s):  
Star Formation ◽  
Intensity Ratio ◽  
Molecular Clouds ◽  
Early Stage ◽  
Infrared Emission ◽  
Radio Continuum ◽  
High Mass ◽  
Continuum Emission ◽  
Mass Star ◽  
H Ii Region

Abstract We report on a study of the high-mass star formation in the H ii region W 28 A2 by investigating the molecular clouds that extend over ∼5–10 pc from the exciting stars using the 12CO and 13CO (J = 1–0) and 12CO (J = 2–1) data taken by NANTEN2 and Mopra observations. These molecular clouds consist of three velocity components with CO intensity peaks at VLSR ∼ −4 km s−1, 9 km s−1, and 16 km s−1. The highest CO intensity is detected at VLSR ∼ 9 km s−1, where the high-mass stars with spectral types O6.5–B0.5 are embedded. We found bridging features connecting these clouds toward the directions of the exciting sources. Comparisons of the gas distributions with the radio continuum emission and 8 μm infrared emission show spatial coincidence/anti-coincidence, suggesting physical associations between the gas and the exciting sources. The 12CO J = 2–1 to 1–0 intensity ratio shows a high value (≳0.8) toward the exciting sources for the −4 km s−1 and +9 km s−1 clouds, possibly due to heating by the high-mass stars, whereas the intensity ratio at the CO intensity peak (VLSR ∼ 9 km s−1) decreases to ∼0.6, suggesting self absorption by the dense gas in the near side of the +9 km s−1 cloud. We found partly complementary gas distributions between the −4 km s−1 and +9 km s−1 clouds, and the −4 km s−1 and +16 km s−1 clouds. The exciting sources are located toward the overlapping region in the −4 km s−1 and +9 km s−1 clouds. Similar gas properties are found in the Galactic massive star clusters RCW 38 and NGC 6334, where an early stage of cloud collision to trigger the star formation is suggested. Based on these results, we discuss the possibility of the formation of high-mass stars in the W 28 A2 region being triggered by cloud–cloud collision.

scholarly journals Radio properties of the OH megamaser galaxy IRAS 02524+2046

2020 ◽  
Vol 638 ◽  
pp. A78
Author(s):  
Hao Peng ◽  
Zhongzu Wu ◽  
Bo Zhang ◽  
Yongjun Chen ◽  
Xingwu Zheng ◽  
...  
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Line Emission ◽  
Far Infrared ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Starburst Galaxy ◽  
Radio Flux ◽  
Vlbi Observations

We present results from VLBI observations of continuum and OH line emission in IRAS 02524+2046 as well as arcsecond-scale radio properties of this galaxy using VLA archive data. We found that there is no significant detection of radio continuum emission from VLBI observations. The arcsecond-scale radio images of this source show no clear extended emission. The total radio flux density at L and C bands are approximately 2.9 mJy and 1.0 mJy, respectively, which indicates a steep radio spectral index between the two bands. A steep spectral index, low brightness temperature, and high q-ratio (i.e., the far-infrared to the radio flux density), which are three critical indicators in the classification of radio activity in the nuclei of galaxies, are all consistent with the classification of this source as a starburst galaxy from its optical spectrum. The high-resolution line profile reveals that we detected both the 1665 MHz and 1667 MHz OH maser lines, which show two and three clear components, respectively. The channel maps show that the maser emission are distributed in a region of ∼210 pc × 90 pc. The detected maser components in different regions indicate similar double spectral features, which might be evidence that this galaxy is at a stage of major merger as seen from the optical morphology.

scholarly journals The Large-Scale Radio Continuum Structure of Spiral Galaxies

1978 ◽  
Vol 77 ◽  
pp. 33-48 ◽  
Author(s):  
P.C. van der Kruit
Keyword(s):  
Large Scale ◽  
Spiral Galaxies ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Optical Image ◽  
Radio Continuum ◽  
Continuum Emission ◽  
The Galaxy ◽  
Continuum Structure ◽  
Disk Component

This review concerns the large-scale structure of radio continuum emission in spiral galaxies (“the smooth background”), by which we mean the distribution of radio surface brightness at scales larger than, say, 1 kpc. Accordingly the nuclear emission and structure due to spiral arms and HII regions will not be a major topic of discussion here. Already the first mappings of the galactic background suggested that there is indeed a distribution of radio continuum emission extending throughout the Galaxy. This conclusion has been reinforced by the earliest observations of M31 by showing that the general emission from this object extended over at least the whole optical image. More recently, van der Kruit (1973a, b, c) separated the radio emission from a sample of spiral galaxies observed at 1415 MHz with the Westerbork Synthesis Radio Telescope (WSRT) into a nuclear, spiral arm and “base disk” component, showing that the latter component usually contains most of the flux density. This latter component is largely non-thermal and extends over the whole optical image (see also van der Kruit and Allen, 1976). Clearly it is astrophysically interesting to discuss the large-scale structure of the radio continuum emission.

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