scholarly journals Warm and Cold Gas in Galactic Nuclei: The Near-IR/Millimeter Connection in NGC 253

1994 ◽  
Vol 140 ◽  
pp. 306-311
Author(s):  
Paul P. Van Der Werf ◽  
M. Cameron ◽  
R. Genzel ◽  
M. Blietz ◽  
A. Krabbe ◽  
...  
Keyword(s):  
Galactic Nuclei ◽  
Spectroscopic Imaging ◽  
Optical Emission ◽  
Starburst Galaxy ◽  
Stellar Content ◽  
Giant Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Near Ir ◽  
Ir Spectroscopic

AbstractWe discuss the use of seeing-limited near-IR spectroscopic imaging combined with high resolution millimeter and submillimeter wave observations, as a diagnostic in the study of the nuclear interstellar medium in starburst galaxies and active galactic nuclei. As an example, recent near-IR spectroscopic imaging of the starburst galaxy NGC 253 is analyzed. It is shown that the central ~ 100 pc of NGC 253 contains a number of giant star forming complexes, the stellar content of which is at least as large as that of the 30 Dor region in the LMC. We suggest the use of the [FeII]/Brγ ratio as an approximate age indicator for such complexes. The warm component of the nuclear molecular medium in NGC 253 detected in submillimeter CO spectra and in near-IR rovibrational lines of H2 is probably heated by stellar UV radiation or slow shocks in star forming regions, rather than by supernova remnant shocks. There are indications that molecular material is being removed from the nuclear region by the “superwind” observed in optical emission lines.

Multiwavelength analysis of OH Megamaser galaxies: The case of IRAS11506-3851

2020 ◽  
Vol 15 (S359) ◽  
pp. 347-349
Author(s):  
Carpes P. Hekatelyne ◽  
Thaisa Storchi-Bergmann
Keyword(s):  
Active Galactic Nuclei ◽  
Hubble Space Telescope ◽  
Galactic Nuclei ◽  
Large Array ◽  
Very Large Array ◽  
Star Forming ◽  
Star Forming Regions ◽  
Field Unit ◽  
Mixed Transition ◽  
Integral Field

AbstractWe present Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Hubble Space Telescope (HST) and Very Large Array (VLA) observations of the inner kpc of the OH Megamaser galaxy IRAS 11506-3851. In this work we discuss the kinematics and excitation of the gas as well as its radio emission. The HST images reveal an isolated spiral galaxy and the combination with the GMOS-IFU flux distributions allowed us to identify a partial ring of star-forming regions surrounding the nucleus with a radius of ≍500 pc. The emission-line ratios and excitation map reveal that the region inside the ring present mixed/transition excitation between those of Starbursts and Active Galactic Nuclei (AGN), while regions along the ring are excited by Starbursts. We suggest that we are probing a buried or fading AGN that could be both exciting the gas and originating an outflow.

scholarly journals VSOP, A Space VLBI Programme

1990 ◽  
Vol 123 ◽  
pp. 263-269
Author(s):  
H. Hirabayashi
Keyword(s):  
Active Galactic Nuclei ◽  
Phase Transfer ◽  
Galactic Nuclei ◽  
Satellite Orbit ◽  
Radio Sources ◽  
Space Observatory ◽  
Stellar Objects ◽  
Radio Observatory ◽  
Star Forming ◽  
Star Forming Regions

AbstractVSOP, VLBI Space Observatory Programme, is an approved space VLBI programme of ISAS for the study of very compact radio sources with the synthesized aperture of 30,000 km diameter, by connecting an orbiting radio observatory with ground radiotelescopes. The VSOP satellite carrying 10 m antenna with 1.6, 5, and 22 GHz band receivers will be launched in early 1995 by M-V rocket of ISAS into an eccentric orbit with 20,000 km in apogee height. The tracking network will be formed for the satellite orbit determination, phase transfer and IF down-link. VSOP aims imaging capability with best resolution of 0.0001 arc second in 22 GHz band. Imaging of active galactic nuclei, star forming regions and stellar objects, and radioastrometry are main scientific targets.

Gamma-ray Observation of Nearby Starburst Galaxy IC342

2005 ◽  
Vol 20 (14) ◽  
pp. 3167-3169
Author(s):  
◽  
Tomoyuki Nagai ◽  
Vladimir Vassiliev
Keyword(s):  
Cosmic Rays ◽  
Gamma Ray ◽  
High Energy ◽  
Critical Parameters ◽  
Starburst Galaxy ◽  
Star Forming ◽  
High Energy Cosmic Rays ◽  
Star Forming Regions ◽  
Progenitor Stars ◽  
Current Paradigm

Regions with high star formation rates (SFR) in starburst galaxies (SBGs) are frequently accompanied by high density clouds of interstellar matter (ISM). This may create nearly perfect conditions for generating diffuse gamma-ray radiation as high energy cosmic rays accelerated in supernovae explosions of massive progenitor stars interact with the ambient protons. If the current paradigm that supernovae are the origin sites of high energy cosmic rays is valid, then the star forming regions rich in supernovae may become the laboratories to test and study this phenomenon. The gamma-ray luminosity of these extragalactic objects is suppressed by a large distance factor compared to supernovae in our own galaxy. However, flux estimates indicate that if star bursting regions have a proper combination of critical parameters (intersteller medium density, age, size, supernova rate, magnetic field strength) the cumulative enhancement of the gamma-ray luminosity resulting from multiple explosions of supernovae into dense ISM may generate an observable flux for nearby SBGs such as M82, IC342. A search for TeV gamma-ray emission from IC342 was conducted with the Whipple 10m gamma-ray telescope from September 2002 to March 2004.

Magnetodynamical acceleration of cosmic jets: sweeping-magnetic-twist mechanism

1986 ◽  
Vol 64 (4) ◽  
pp. 507-513 ◽  
Author(s):  
Yutaka Uchida ◽  
Kazunari Shibata
Keyword(s):  
Large Scale ◽  
Galactic Nuclei ◽  
High Energy ◽  
Point Of View ◽  
Driving Mechanism ◽  
Star Forming ◽  
Star Forming Regions ◽  
Large Scale Magnetic Field ◽  
Twisted Field ◽  
The Galaxy

Characteristic behavior of cosmic jets predicted by a magnetodynamic mechanism proposed by Uchida and Shibata is discussed in terms of recent observational results of bipolar flows from star-forming regions as examples of low-energy cases. The theoretical model considers the twisting-up of part of the large-scale magnetic field with the driving mechanism being the contracting rotation of the accretion disk around the gravitating center. The twisted field screws out the mass from the surface layers of the disk along the large-scale external field, explaining the observed tuning-fork type of distribution of the cold CO bipolar flows, gradual acceleration of the flows from the vicinity of the disk, and the helical velocity field in the outflows, all of which are not easy to explain by previous hypotheses assuming the wind and blast from the central object. Prospects of application of this mechanism to high-energy jets from active galactic nuclei or such peculiar objects in the galaxy like SS433 or Sco X-1 are discussed from the point of view of the similarity inherent in the mechanism.

scholarly journals Stellar Associations in the LMC

1999 ◽  
Vol 190 ◽  
pp. 410-416 ◽  
Author(s):  
E. Kontizas ◽  
M. Kontizas ◽  
D. Gouliermis ◽  
A. Dapergolas ◽  
R. Korakitis ◽  
...  
Keyword(s):  
Star Formation History ◽  
Stellar Content ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Stellar Component ◽  
Formation History ◽  
Wide Range ◽  
Definition Of ◽  
Stellar Associations

The stellar associations are defined as loose unbound concentrations of young stars with a bright OB stellar component, mainly located at the most recent star forming regions, representing the smallest units in the hierarchy of stellar systems in galaxies. The definition of the associations is discussed and the main properties of their stellar content are summarized. Using plates taken with the 1.2m UK Schmidt Telescope a method is developed to detect all stellar associations in the LMC and to find their spatial distribution relative to the LMC's recent star formation history. In 40% of the LMC region, the number of “single peak” associations has increased considerably (~ 3x). A very interesting result is that the faint limit, where the identified associations are revealed, varies by about 3 mag. This indicates not only extinction differences but also the presence of pre-main sequence stars at a wide range of masses.

scholarly journals An obscured AGN population hidden in the VIPERS galaxies: identification through spectral energy distribution decomposition

2020 ◽  
Vol 495 (2) ◽  
pp. 1853-1873
Author(s):  
E Pouliasis ◽  
G Mountrichas ◽  
I Georgantopoulos ◽  
A Ruiz ◽  
M Yang ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Galactic Nuclei ◽  
Spectral Energy ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Redshift Survey ◽  
Selection Of

ABSTRACT The detection of X-ray emission constitutes a reliable and efficient tool for the selection of active galactic nuclei (AGNs), although it may be biased against the most heavily absorbed AGNs. Simple mid-infrared (IR) broad-band selection criteria identify a large number of luminous and absorbed AGNs, yet again host contamination could lead to non-uniform and incomplete samples. Spectral energy distribution (SED) decomposition is able to decouple the emission from the AGN versus that from star-forming regions, revealing weaker AGN components. We aim to identify the obscured AGN population in the VIMOS Public Extragalactic Redshift Survey in the Canada–France–Hawaii Telescope Legacy Survey W1 field through SED modelling. We construct SEDs for 6860 sources and identify 160 AGNs at a high confidence level using a Bayesian approach. Using optical spectroscopy, we confirm the nature of ∼85 per cent of the AGNs. Our AGN sample is highly complete (∼92 per cent) compared to mid-IR colour-selected AGNs, including a significant number of galaxy-dominated systems with lower luminosities. In addition to the lack of X-ray emission (80 per cent), the SED fitting results suggest that the majority of the sources are obscured. We use a number of diagnostic criteria in the optical, IR, and X-ray regimes to verify these results. Interestingly, only 35 per cent of the most luminous mid-IR-selected AGNs have X-ray counterparts suggesting strong absorption. Our work emphasizes the importance of using SED decomposition techniques to select a population of type II AGNs, which may remain undetected by either X-ray or IR colour surveys.

scholarly journals Water in the interstellar media of galaxies

2015 ◽  
Vol 11 (A29B) ◽  
pp. 395-399
Author(s):  
Floris F. S. van der Tak
Keyword(s):  
High Resolution ◽  
Water Chemistry ◽  
Galactic Nuclei ◽  
Radiation Environment ◽  
Interstellar Clouds ◽  
Star Forming ◽  
Star Forming Regions ◽  
Interstellar Media ◽  
Ionization Rates

AbstractThis paper reviews recent observations of water in Galactic interstellar clouds and nearby galactic nuclei. Two results are highlighted: (1) Multi-line H2O mapping of the Orion Bar shows that the water chemistry in PDRs is driven by photodissociation and -desorption, unlike in star-forming regions. (2) High-resolution spectra of H2O and its ions toward 5 starburst / AGN systems reveal low ionization rates, unlike as found from higher-excitation lines. We conclude that the chemistry of water strongly depends on radiation environment, and that the ionization rates of interstellar clouds decrease by at least 10 between galactic nuclei and disks.

scholarly journals SEQUENTIAL STAR FORMATION IN RCW 34: A SPECTROSCOPIC CENSUS OF THE STELLAR CONTENT OF HIGH-MASS STAR-FORMING REGIONS

2010 ◽  
Vol 713 (2) ◽  
pp. 883-899 ◽  
Author(s):  
A. Bik ◽  
E. Puga ◽  
L.B.F.M. Waters ◽  
M. Horrobin ◽  
Th. Henning ◽  
...  
Keyword(s):  
Star Formation ◽  
High Mass ◽  
Mass Star ◽  
Stellar Content ◽  
Star Forming ◽  
Star Forming Regions
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