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TOPIC: NGC 1808

Blobrana

L

Posts: 131433

Date: Dec 21 14:57 2016

RE: NGC 1808	Permalink

Title: Multi-line Imaging of the Starburst Galaxy NGC 1808 with ALMA Author: Dragan Salak, Yuto Tomiyasu, Naomasa Nakai, Yusuke Miyamoto Revealing the properties of molecular gas in starburst galaxies is key to understand the process of star formation across cosmic history. In this paper, we present our recent high-resolution (\(\sim1''\) or 50 pc) ALMA observations of the nearby, barred starburst galaxy NGC 1808, and highlight some of the main findings: (1) the discovery of a double peak revealed in the distributions of CO (3-2) and CS (2-1) in the circumnuclear disk indicating the presence of a molecular gas torus with a radius of \(r\sim32\) pc; inside the torus, we found a compact source of dust continuum at 0.87 mm and CO, coincident with the location of the low-luminosity AGN revealed by X-ray observations; (2) the excitation of CO gas, traced by the line intensity ratio of CO (3-2) to CO (1-0) is elevated to \(\sim1\) in the star-forming disk; the ratio is between 0.5 and 1 in the 500 pc ring; (3) the ratio of HCN (1-0) to HCO\(^{+}\) (1-0) in the central 1 kpc exhibits a radial gradient: while the ratio decreases from \(\sim1.6\) in the center to \(\sim0.9\) in the 500 pc disk, it exhibits a peak of \(\sim2\) in a ring-like structure at a galactocentric radius of \(r\sim100\) pc. The detection of SiO (2-1) within the CND suggests the presence of shocks, likely generated by the intense nuclear star formation (supernova explosions and stellar winds from massive stars), as well as inflows and outflows of turbulent gas in the central 100 pc. Read more (4843kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Dec 5 15:17 2016

PGC 16779	Permalink

Title: Star formation and gas flows in the centre of the NUGA galaxy NGC 1808 observed with SINFONI Author: Gerold Busch, Andreas Eckart, Mónica Valencia-S., Nastaran Fazeli, Julia Scharwächter, Françoise Combes, Santiago García-Burillo NGC 1808 is a nearby barred spiral galaxy which hosts young stellar clusters in a patchy circumnuclear ring with a radius of ~240pc. In order to study the gaseous and stellar kinematics and the star formation properties of the clusters, we perform seeing-limited H+K-band near-infrared integral-field spectroscopy with SINFONI of the inner ~600pc. From the M^BH - sigma_* relation, we find a black hole mass of a few 10^7 solar masses. We estimate the age of the young stellar clusters in the circumnuclear ring to be \lesssim 10Myr. No age gradient along the ring is visible. However, the starburst age is comparable to the travel time along the ring, indicating that the clusters almost completed a full orbit along the ring during their life time. In the central ~600pc, we find a hot molecular gas mass of ~730 solar masses which, with standard conversion factors, corresponds to a large cold molecular gas reservoir of several 10^8 solar masses, in accordance with CO measurements from the literature. The gaseous and stellar kinematics show several deviations from pure disc motion, including a circumnuclear disc and signs of a nuclear bar potential. In addition, we confirm streaming motions on ~200pc scale that have recently been detected in CO(1-0) emission. Due to our enhanced angular resolution of <1arcsec, we find further streaming motion within the inner arcsecond, that have not been detected until now. Despite the flow of gas towards the centre, no signs for significant AGN activity are found. This raises the questions what determines whether the infalling gas will fuel an AGN or star formation. Read more (3101kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: May 9 20:48 2014

NGC 1808	Permalink

NGC 1808 (also IRAS 05059-3734, MCG -6-12-5 and PGC 16779) is a magnitude +10.8 Seyfert galaxy located 46 million light-years away in the constellation Columba. NGC 1808 is probably a neighbour of, and gravitationally interacting with, NGC 1792. The galaxy was discovered by Scottish astronomer James Dunlop using a 22.86 cm (9 inch) Reflector at Paramatta (now named Parramatta), New South Wales on the 10 May 1826. The galaxy hosted Supernova 1993AF Right Ascension 05h 07m 42.5s, Declination -37° 30' 47" Read more Read more __________________

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