scholarly journals Molecular Gas Distribution and Dynamics in the Central Region of Galaxies

1994 ◽  
Vol 140 ◽  
pp. 293-299
Author(s):  
Sumio Ishizuki
Keyword(s):  
High Resolution ◽  
Central Region ◽  
Large Scale ◽  
Starburst Galaxies ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Molecular Gas ◽  
Gas Distribution

AbstractTo investigate the relation between a large-scale stellar bar and circumnuclear starburst, the CO (J=1→0) emission of circumnuclear regions of three starburst galaxies NGC2782, NGC3504, and M83 (NGC5236) have been mapped with the Nobeyama Millimeter Array. The high resolution CO (J=1→0) images indicate that the molecular gas in the three starburst galaxies is located interior to the innermost ends of the paired straight dust lanes. The molecular gas at the small radii is associated with their circumnuclear starburst sites which are indicated by radio continuum emission.

scholarly journals The Circumstellar Environment of LkHα 234

1987 ◽  
Vol 115 ◽  
pp. 368-368
Author(s):  
B. A. Wilking ◽  
L. G. Mundy ◽  
R. D. Schwartz
Keyword(s):  
High Resolution ◽  
Millimeter Wave ◽  
Spectral Dependence ◽  
Large Scale ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Owens Valley ◽  
Molecular Line ◽  
Continuum Source ◽  
Circumstellar Environment

We present high resolution (HPBW = 5 arcsec) continuum and molecular-line observations of the circumstellar environment of the emission-line star LkHα 234 made with the Owens Valley Millimeter-Wave Interferometer. These 98 GHz observations have revealed an unresolved continuum source coincident with the star and a 10 000 by 17000 A.U. ridge of enhanced CS(2-1) emission which peaks ∼ 4″ east of the star. The resulting spectral dependence for the radio continuum emission of ν1.5 is most easily interpreted as arising from a partially ionized stellar wind. Attempts are made to describe the properties of the CS emission in terms of a rotating molecular disk which would link LkHα 234 with large scale mass loss activity in the cloud. However, it appears most likely that the CS emission is arising from a dense (n(H2) ∼ 106 cm −3) condensation of gas adjacent to, but not dynamically associated with, the star.

scholarly journals A Survey of OH in the Galactic Centre Region

1996 ◽  
Vol 169 ◽  
pp. 311-316
Author(s):  
P.J. Boyce ◽  
R. J. Cohen
Keyword(s):  
Central Region ◽  
Molecular Clouds ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Molecular Gas ◽  
The Galaxy ◽  
Centre Region ◽  
Line Survey ◽  
The Continuum

The galactic centre contains the largest concentration of molecular clouds in the Galaxy. The clouds in the central region are unusual in having large linewidths and masses, and large non-circular motions. Previous surveys of their distribution in the central region have been carried out in OH (Robinson & McGee 1970; Cohen & Few 1976), H2CO (Whiteoak & Gardner 1979; Cohen & Few 1981), CO (Bania 1977; Dame et al. 1987; Bally et al. 1987, 1988) and CS (Bally et al. 1987, 1988). The OH groundstate lines at 18cm wavelength have certain advantages for such a survey. The OH lines appear in absorption against the galactic centre continuum sources, and against the continuum emission from the disk of the Galaxy. The absorption spectra are sensitive to relatively small molecular column densities. In addition they can give information on the relative positions of the molecular gas and the radio continuum sources. This paper describes results from an absorption line survey of the galactic centre region in the OH main lines at 1667.359 MHz and 1665.402 MHz (Boyce & Cohen 1994).

scholarly journals Molecules as tracers of galaxy evolution

2012 ◽  
Vol 8 (S292) ◽  
pp. 199-208 ◽  
Author(s):  
Susanne Aalto
Keyword(s):  
Black Holes ◽  
Star Formation ◽  
High Resolution ◽  
Galaxy Evolution ◽  
Large Scale ◽  
Short Review ◽  
Stimulated Emission ◽  
Molecular Gas ◽  
Infrared Galaxies ◽  
Luminous Infrared Galaxies

AbstractStudying the molecular phase of the interstellar medium in galaxies is fundamental for the understanding of the onset and evolution of star formation and the growth of supermassive black holes. We can use molecules as observational tools exploiting them as tracers of chemical, physical and dynamical conditions. In this short review, key molecules (e.g. HCN, HCO+, HNC, HC3N, CN, H3O+) in identifying the nature of buried activity and its evolution are discussed including some standard astrochemical scenarios. Furthermore, we can use IR excited molecular emission to probe the very inner regions of luminous infrared galaxies (LIRGs) allowing us to get past the optically thick dust barrier of the compact obscured nuclei, e.g. in the dusty LIRG NGC4418. High resolution studies are often necessary to separate effects of excitation and radiative transport from those of chemistry - one example is absorption and effects of stimulated emission in the ULIRG Arp220. Finally, molecular gas in large scale galactic outflows is briefly discussed.

scholarly journals The TANGO Project: Thorough ANalysis of radio-Galaxies Observations

2009 ◽  
Vol 5 (S267) ◽  
pp. 127-127
Author(s):  
Breezy Ocaña Flaquer ◽  
Stephane Leon Tanne ◽  
Francoise Combes ◽  
Jeremy Lim
Keyword(s):  
Selection Criteria ◽  
Radio Galaxies ◽  
Elliptical Galaxies ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Molecular Gas

AbstractWe present a sample of radio galaxies selected only on the basis of radio continuum emission and we confirm that these galaxies have lower molecular gas mass than other elliptical galaxies with different selection criteria.

scholarly journals A coordinated radio and optical survey of M31

1985 ◽  
Vol 106 ◽  
pp. 435-436
Author(s):  
R.A.M. Walterbos ◽  
R. C. Kennicutt
Keyword(s):  
Large Scale ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Small Scale ◽  
Surface Photometry ◽  
Optical Surface ◽  
Schmidt Telescope ◽  
Infrared Observations ◽  
Andromeda Galaxy ◽  
Optical Surveys

At Leiden we are obtaining coordinated radio, optical and infrared observations of the Andromeda galaxy, M31. Its proximity offers us a unique opportunity to study both the large-scale and small-scale structure of a galaxy which is similar in many respects to the Milky Way. The WSRT has been used to obtain high-resolution (24″ × 36″) maps of M31 in the HI line and 21-and 49-cm radio-continuum emission. Recently the radio data have been complemented with optical surface photometry in UBVR and Hα, using the Burrell Schmidt telescope at Kitt Peak and the Palomar Schmidt. Results from the HI and IRAS infrared observations are presented elsewhere. Here we present some preliminary results from the radio-continuum and optical surveys.

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.

scholarly journals Characterizing the radio continuum emission from intense starburst galaxies

2016 ◽  
Vol 461 (1) ◽  
pp. 825-838 ◽  
Author(s):  
T. J. Galvin ◽  
N. Seymour ◽  
M. D. Filipović ◽  
N. F. H. Tothill ◽  
J. Marvil ◽  
...  
Keyword(s):  
Starburst Galaxies ◽  
Radio Continuum ◽  
Continuum Emission

scholarly journals CTB80: Cosmic Collision?

1983 ◽  
Vol 101 ◽  
pp. 343-346
Author(s):  
C. J. Salter ◽  
F. Mantovani ◽  
P. Tomasi
Keyword(s):  
High Resolution ◽  
Radio Source ◽  
Radio Continuum ◽  
Continuum Emission ◽  
X Ray ◽  
Polarized Emission ◽  
Linearly Polarized ◽  
New Interpretation ◽  
Galactic Radio

High resolution maps of the Galactic radio source CTB80 at three different frequencies are presented. A new interpretation in terms of a cosmic collision between two SNRs of different age is suggested.CTB80 is one of the most mystifying Galactic Objects yet discovered and has recently attracted considerable attention from X-ray, optical and radio astronomers (see for example: Becker et al. (1981), Angerhofer et al. (1980, 1981), Velusamy et al. (1976), van den Bergh (1980).The present observations of the radio continuum emission of the extended feature at 408 MHz, 1720 MHz and 4750 MHz and the linearly polarized emission at 1720 MHz and 4750 MHz (Figs 1,2,3) throw new light on the morphological, spectral and polarization properties of the whole source.

scholarly journals The headlight cloud in NGC 628: An extreme giant molecular cloud in a typical galaxy disk

2020 ◽  
Vol 634 ◽  
pp. A121 ◽  
Author(s):  
Cinthya N. Herrera ◽  
Jérôme Pety ◽  
Annie Hughes ◽  
Sharon E. Meidt ◽  
Kathryn Kreckel ◽  
...  
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Stellar Population ◽  
High Mass ◽  
Molecular Gas ◽  
Giant Molecular Cloud ◽  
The Impact

Context. Cloud-scale surveys of molecular gas reveal the link between giant molecular cloud properties and star formation across a range of galactic environments. Cloud populations in galaxy disks are considered to be representative of the normal star formation process, while galaxy centers tend to harbor denser gas that exhibits more extreme star formation. At high resolution, however, molecular clouds with exceptional gas properties and star formation activity may also be observed in normal disk environments. In this paper we study the brightest cloud traced in CO(2–1) emission in the disk of nearby spiral galaxy NGC 628. Aims. We characterize the properties of the molecular and ionized gas that is spatially coincident with an extremely bright H II region in the context of the NGC 628 galactic environment. We investigate how feedback and large-scale processes influence the properties of the molecular gas in this region. Methods. High-resolution ALMA observations of CO(2–1) and CO(1−0) emission were used to characterize the mass and dynamical state of the “headlight” molecular cloud. The characteristics of this cloud are compared to the typical properties of molecular clouds in NGC 628. A simple large velocity gradient (LVG) analysis incorporating additional ALMA observations of 13CO(1−0), HCO+(1−0), and HCN(1−0) emission was used to constrain the beam-diluted density and temperature of the molecular gas. We analyzed the MUSE spectrum using Starburst99 to characterize the young stellar population associated with the H II region. Results. The unusually bright headlight cloud is massive (1 − 2 × 107 M⊙), with a beam-diluted density of nH2 = 5 × 104 cm−3 based on LVG modeling. It has a low virial parameter, suggesting that the CO emission associated with this cloud may be overluminous due to heating by the H II region. A young (2 − 4 Myr) stellar population with mass 3 × 105 M⊙ is associated. Conclusions. We argue that the headlight cloud is currently being destroyed by feedback from young massive stars. Due to the large mass of the cloud, this phase of the its evolution is long enough for the impact of feedback on the excitation of the gas to be observed. The high mass of the headlight cloud may be related to its location at a spiral co-rotation radius, where gas experiences reduced galactic shear compared to other regions of the disk and receives a sustained inflow of gas that can promote the mass growth of the cloud.

scholarly journals 5.5. The detection of a gas-rich bar in the interacting galaxy UGC 2855

1998 ◽  
Vol 184 ◽  
pp. 219-220
Author(s):  
S. Hüttemeister ◽  
S. Aalto ◽  
W. F. Wall
Keyword(s):  
Star Formation ◽  
Central Region ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Starburst Galaxies ◽  
Large Percentage ◽  
Molecular Gas ◽  
Transient Phenomena

Bars fuel the prolific star formation rate in many Starburst galaxies. They provide a mechanism for feeding gas into the nuclei as well as a laboratory for the study of molecular gas that is unbound and diffuse due to tidal strain and cloud collisions. A large percentage of galaxies show a stellar bar which is, however, in most cases almost devoid of (molecular) gas, except in the central region. Thus, long gaseous bars are rare and transient phenomena.

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