* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Home -> Astronomy News -> Stars/galaxy News -> NGC 34
Post Info TOPIC: NGC 34
Blobrana


L

Posts: 131433
Date:
RE: NGC 34
Permalink  
 

Title: Discovery of a Small Central Disk of CO and HI in the Merger Remnant NGC 34
Author: Ximena Fernández, A.O. Petric, Francois Schweizer, J.H. van Gorkom

We present CO(1-0) and HI(21-cm) observations of the central region of the wet merger remnant NGC 34. The Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations detect a regularly rotating disk in CO with a diameter of 2.1 kpc and a total molecular hydrogen mass of (2.1±0.2)×109 M. The rotation curve of this gas disk rises steeply, reaching maximum velocities at 1" (410 pc) from the center. Interestingly, HI observations done with the Karl G. Jansky Very Large Array show that the absorption against the central continuum has the exact same velocity range as the CO in emission. This strongly suggests that the absorbing HI also lies within 1" from the center, is mixed in and corotates with the molecular gas. A comparison of HI absorption profiles taken at different resolutions (5"-45") shows that the spectra at lower resolutions are less deep at the systemic velocity. This provides evidence for HI emission in the larger beams, covering the region from 1 kpc to 9 kpc from the center. The central rapidly rotating disk was likely formed either during the merger or from fall-back material. Lastly, the radio continuum flux of the central source at mm wavelengths (5.4±1.8 mJy) is significantly higher than expected from an extrapolation of the synchrotron spectrum, indicating the contribution of thermal free-free emission from the central starburst.

Read more (1986kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: Remnant of a "Wet" Merger: NGC 34 and Its Young Massive Clusters, Young Stellar Disk, and Strong Gaseous Outflow
Authors: Francois Schweizer (OCIW), Patrick Seitzer (U. Michigan)

This paper presents new images and spectroscopy of NGC 34 (Mrk 938) obtained with the du Pont 2.5-m and Baade 6.5-m telescopes at Las Campanas, plus photometry of an HST archival V image. This Mv = -21.6 galaxy has often been classified as a Seyfert 2, yet recently published infrared spectra suggest a dominant central starburst. We find that the galaxy features a single nucleus, a main spheroid containing a blue central disk, and tidal tails indicative of two former disk galaxies. These galaxies appear to have completed merging. The remnant shows three clear optical signs that the merger was gas-rich ("wet") and accompanied by a starburst: (1) It sports a rich system of young star clusters, of which 87 have absolute magnitudes -10.0 > Mv > -15.4. Five clusters with available spectra have ages in the range 0.1-1.0 Gyr, photometric masses between 2x10^6 and 2x10^7 Msun, and are gravitationally bound young globulars. (2) The blue central disk appears to be young. It is exponential, can be traced to >10 kpc radius, and has a smooth structure and colours suggest- ing a dominant, ~400 Myr old poststarburst population. And (3), the centre of NGC 34 drives a strong outflow of cool, neutral gas, as revealed by broad blueshifted Na I D lines. The mean outflow velocity of this gas is -620 km/s, while the maximum velocity reaches -1050 km/s. We suggest that NGC 34 stems from two recently merged gas-rich disk galaxies with an estimated mass ratio between 1/3 and 2/3. The remnant seems to have first experienced a galaxy-wide starburst that then shrank to its current central and obscured state. The strong gaseous outflow came last.

Read more (771kb, PDF)

__________________
Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.
Home -> Astronomy News -> Stars/galaxy News -> NGC 34


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard