Scientific Highlights


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Scientific Highlights    


      

Due to the upgrade of the telescope control system (described in detail in the Technical Section), actual astronomical operation of the SMT after summer 2002 shutdown was not resumed until November 2002. In spite of this shortened time span, several exciting developments have occurred. Not only has the use of the current facility instruments been consolidated (especially in continuum), but also several new receiver systems (JT, Desert STAR) have been tested for the first time. Furthermore, mm-wave VLBI operations involving the 2 antennas of ARO are now well established, having made possible the first successful transatlantic 1mm observations ever. Below is a brief summary of the observations carried out since then, and some of the results.

 

Spectral Line Studies:

Star formation regions in the Galaxy

Hails et al mapped CS(5-4) in several molecular regions near known sites of massive star formation in search for high-mass protostellar object precursors.

Hedden et al. mapped the Northern Cloud of the Mon OB1 region in several species and transitions (i.e., CO(3-2), 13CO(3-2), CS(5-4) and CS(7-6)) to better understand the dynamical and physical conditions in and around the star forming ridges.

Wilson et al. mapped specific regions of the M17 molecular complex in the CO(3-2) and CS(7-6) lines to compare with their VLA SiO(1-0) map of those regions.

Young Stellar objects

To support their detections of HCN(4-3) v=1 1c mode vibrational emission from putative circumstellar disks, Groppi et al. observed the  1d mode emission in several candidates.

Interstellar Chemistry

Ruiterkamp et al. observed several transitions of the HNCO molecule in protostars with the 4.62 micron XCN spectral absorption feature to investigate the possibility that they are related.

Savage et al observed the hyperfine N=2→1 and N=3→2 transitions of CN and 13CN in the 1mm region to better determine the isotopic 12C/13C ratios in several molecular clouds.

Ziurys et al were the first to use the new JT 2mm facility receiver for astronomical observations. They have started a project to search for Calcium Carbide (CaC) in several carbon-rich environments.

In order to study the possible presence of chemical differentiation in regions with moderate star formation levels, Butner et al carried out a multi-line and multi-transition mapping project of the B5 and L1641N regions in CS, CH3OH, H13CO and C18O.

Extragalactic Astronomy

Apponi et al carried out a survey of 10 early-type galaxies with detected ISM (X-rays, HI and dust) in CO(2-1) and CO(3-2) to obtain information on the physical conditions of the molecular gas in these objects. Data on the CO(1-0) transition were obtained at the other telescope of the Arizona Radio Observatory (KP12m).

Vila-Vilaro et al started their high frequency study of rare CO isotopes of a sub-sample of RSA spirals they had detected in 13CO(1-0) with the ARO KP12m telescope. They expect to detect secular as well as Hubble type trends. 

 


Continuum Observations:

Planetary

Sykes et al used the 19 channel bolometer to study the sub-mm light curves of two asteroids, Ceres and Vesta. They intend to derive not only the effects of rotational shape variation in the continuum variability but also associate some of the light curve features with actual geographic features on the surfaces of both objects.

Stellar

Meyer et al searched for 870micron dust emission from possible circumstellar disks in a sample of 43 nearby solar-type stars covering a wide range of ages. These data will complement one of the SIRTF legacy programs that intend to study the structure of such disks, their frequency and their evolution until planet condensation.

Bieging observed the thermal dust emission in the circumstellar envelopes of 30 AGB stars with previously detected CO emission. Such measurements will allow determining the dust-to-gas ratio of the ejected material. Most objects were detected.

  

 

 Silverstone et al measured the thermal dust emission flux from a sample of 21 main-sequence stars detected by IRAS. The data will help determine the total mass of optically thick dust and the amount of cool dust in their circumstellar disks.

Stansberry et al searched for the presence of circumstellar disks around lambda-Bootis stars and nearby binary systems. The presence of such disks in the former would support the view that their abnormal abundances come from peculiar selective condensation of metals. In the latter it will help study the stability and evolution of such disks in binary stellar systems.

Aufdenberg & Gordon studied the thermal dust emission of 6 nearby supergiants to constrain atmospheric models and thus allow a better estimation of mass-loss rates and effective surface temperatures.

Extragalactic

Vila-Vilaro et al studied the 870 micron thermal dust emission in the central regions of 3 bona-fide Seyfert galaxies to prove the possible shocks in those regions. This study will help trace the path of the ISM into the bulges of these objects.


 

The 3-2-1 Survey 

The feasibility of several large-scale spectral-line galactic and extragalactic surveys involving both ARO telescopes has also been tested during this season.

The 3-2-1 Survey proposed by J. Bally (CASA), J. Bieging (SO), C. Walker (SO) and B. Vila-Vilaro (ARO) is aimed at obtaining high-resolution and high-sensitivity mm and sub-mm spectral mapping of 75 square degrees of the Galaxy. This survey will significantly contribute to our understanding of the molecular cloud life-cycles, star formation triggering and self-regulation and the effects of the galactic environment. This survey involves extensive use of the on-the-fly (OTF) mapping technique. To test the technical feasibility of the stringent sensitivity and mapping fidelity requirements for this survey, OTF observations of several selected fields in the molecular ring and anti-center regions were carried out with both the HHSMT and the KP12m telescopes. Preliminary results indicate that at the SMT the required sensitivity can be achieved for a full square degree area in 24 hours of observations.

Figure 1 shown in the OTF mapping section, indicates a contour map of the Gem OB1 region in 12CO(2-1) obtained during the testing.

                 

                Fig 1                        Fig 2                                  Fig 3

Figure 1 A 12CO(2-1) map of the Gem OB1 region obtained using OTF mapping at the HHSMT. The image shows the line integrated intensity, in antenna temperature units, smoothed to the beamsize of the telescope at this frequency (i.e., 32"). The contours range from 10 to 140 K km/s in steps of 5 K km/s. The antenna beam is shown in the small box in the upper righthand corner. Approximately 87,000 spectra have gone into this 0.75deg x 1deg map. An RMS of 0.25 K per binned point was reached for the whole map in 22 hours of observation.

Figure 2. 12CO(2-1) map of a 20' x 1 deg region in the Gem OB1 region obtained with the KP12m telescope. The image shows the line integrated intensity in antenna temperature scale, smoothed to the beamsize of the telescope at this frequency (i.e., 27"). The map can be compared with the one obtained at the HHSMT shown above. 92000 spectra were used in producing this image.

Figure 3. 12CO(2-1) map of a 20' x 1 deg region along the l=30 region (molecular ring) in the Galaxy obtained with the KP12m telescope. The image shows line integrated intensity, in antenna temperature units, smoothed to the beamsize for the telescope at this frequency (i.e., 27").As can be noticed, emission has been detected everywhere in this region. The beam of the telescope is shown in the lower-left of the map. 92000 spectra were used in producing this image.


 

VLBI:

Doeleman, Krichbaum et al carried out 2mm and 1mm continental and transatlantic VLBI observations involving the 2 antennas of the ARO. Spectral line SiO maser observations at 144.NNN GHz of several stellar envelopes were carried out, as well as continuum observations of the central regions of several radio-loud galaxies.

Furthermore, the first successful transatlantic 1mm continuum observations ever were also performed on several strong Active Galactic Nuclei.

 

              

     Fig 1                           Fig 2                     Fig 3

Figure 1:  Optical HST image of the asymmetric VY CMa reflection nebula (Smith et al 2001) showing emission to the SW with almost no emission to the NE of the star.  The faint and reddened NE emission may be due to obscuration from a circumstellar disk oriented SE-NW.

Figure 2:  Velocity color coded map of the v=1 J=32 (129 GHz) SiO masers towards the evolved hypergiant star VY CMa.  The white disk shows the estimated size of the stellar photosphere.  The masers cannot be registered to the stellar position, but their quasi-linear morphology suggests they form either in an incomplete ring around the star, or in a circumstellar disk. 

Figure 3: First transatlantic VLBI fringes at 230 GHz. The continuum emission of the quasar 3C454.3 was detected over the 6 Gigalambda baseline between the HHT and the IRAM 30m stations. The equivalent angular resolution of the observations was 35 µarcseconds"


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Last updated: 11/08/11.