The warm, dense gas in the central two parsecs of the Galaxy: Observations with SPIFI, a new direct-detection submillimeter spectrometer

Details The warm, dense gas in the central two parsecs of the Galaxy: Observations with SPIFI, a new direct-detection submillimeter spectrometer The warm, dense gas in the central two parsecs of the Galaxy: Observations with SPIFI, a new direct-detection submillimeter spectrometer

May 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt........13b&link_type=abstract

Thesis (PhD). CORNELL UNIVERSITY, Source DAI-B 61/11, p. 5911, May 2001, 177 pages.

Mathematics

Logic

1

Scientific paper

We have mapped the central two parsecs of the Galaxy in the J = 7 --> 6 (372 μm) rotational transition of carbon monoxide. The CO emission is generally but not entirely interior to the circumnuclear ring (CNR) traced with HCN emission, and shows some of the morphological features of the far- infrared continuum. An excitation model fit to our observations and existing CO datasets show that the emission originates in warm, T = 240 K, moderate-density, n ~ 7 × 10 4 cm-3, gas with a total mass of 2000-3000 Msolar . The luminosity source is likely magnetohydrodynamic shocks with low velocities, 10-20 km s-1 and modest magnetic fields, 0.3-0.5 mG. The observed luminosity suggests that a substantial fraction (10-50%) of the dynamical energy of the CNR is dissipated on an orbital timescale. We also present a study of the conditions in the starburst nucleus of NGC 253, using observations of far- infrared transitions of OH and CO ( J = 7 --> 6). Optically thin OH absorption transitions measure the column density of OH, and the implied OH abundance is 9 × 10 -7, higher than in any known galactic sources. This can be explained as a combination of the increased metallicity of NGC 253, and enhancement due to warm-gas chemistry. The CO observations show that approximately 25% of the molecular gas in the central 220 pc of NGC 253 is both warmer than 100 K and denser than 104 cm-3. The atomic and warm molecular gas tracers suggest a highly fragmented ISM clumped on scales smaller than 1 pc. The submillimeter observations were made on the first observing run with a new spectrometer, SPIFI. The instrument is the first direct-detection imaging submillimeter spectrometer, and important aspects of its design, construction, and operation are presented. 25 silicon bolometers cooled to 60 mK form the detector array and two cryogenic, scanning Fabry-Perot interferometers and a 60 mK bandpass filter provide spectral resolving power selectable between 500 and 10000. At present, SPIFI's sensitivity is within a factor 1.5-2.5 of the photon background limit, and the instrument has a substantial advantage over present-day heterodyne spectrometers for mapping projects and deep extragalactic observations requiring large bandwidth.

Affiliated with

Also associated with

No associations

Rating

The warm, dense gas in the central two parsecs of the Galaxy: Observations with SPIFI, a new direct-detection submillimeter spectrometer does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The warm, dense gas in the central two parsecs of the Galaxy: Observations with SPIFI, a new direct-detection submillimeter spectrometer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The warm, dense gas in the central two parsecs of the Galaxy: Observations with SPIFI, a new direct-detection submillimeter spectrometer will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-946384