Rui-qing Mao - Academia.edu (original) (raw)
Papers by Rui-qing Mao
Astronomy and Astrophysics, 2007
Aims. The high angular resolution images with the Very Large Array (VLA) allow us to explore the ... more Aims. The high angular resolution images with the Very Large Array (VLA) allow us to explore the general properties of protostellar cores in massive star forming regions at large distances. Methods. We observed the NH 3 (J, K) = (1, 1) and (2, 2) lines toward five massive protostar candidates (IRAS 18196-1331, IRAS 18352-0148, IRAS 18361-0627, IRAS 18414-0339 and IRAS 19474+2637) with the VLA D configuration. Results. We found that these objects have hundreds of solar masses in dense gas with rotation temperatures from 8 to 27 K. No 1.3 cm continuum emission was detected at an rms of ∼0.7 mJy in all sources except IRAS 18361-0627. We identified 60 clumps and determined their physical parameters (e.g. line width, rotation temperature, size, and mass). The clump masses range from 0.1 M ⊙ to 4800 M ⊙ . The average size, line width and temperature are 0.1 ± 0.06 pc, 1.3 ± 0.4 km s −1 and 16 ± 5 K. The discrepancy between NH 3 and (sub)mm continuum emission is found in IRAS 18196-1331. This phenomenon could occur as a result of the NH 3 abundance variation being affected by the UV illumination.
This paper describes observations of search for H2O masers using 13.7 m radio telescope in 1993. ... more This paper describes observations of search for H2O masers using 13.7 m radio telescope in 1993. The sources were selected on the basis of infrared observations of star masers at Xinlong Station, Beijing Astronomical Observatory.
Astronomy & Astrophysics - ASTRON ASTROPHYS, 2000
We surveyed 81 dense molecular cores associated with regions of massive star formation and Sgr A ... more We surveyed 81 dense molecular cores associated with regions of massive star formation and Sgr A in the JK-1K-1 = 505-404 and 10010-909 lines of HNCO. Line emission was detected towards 57 objects. Selected subsamples were also observed in the 101-000, 404-303, 707-606, 15015-14014, 16016-15015 and 21021-20020 lines, covering a frequency range from 22 to 461 GHz. HNCO lines from the K-1 = 2,3 ladders were detected in several sources. Towards Orion-KL, K-1 = 5 transitions with upper state energies Eu/k ~ 1100 and 1300 K could be observed. Five HNCO cores were mapped. The sources remain spatially unresolved at 220 and 461 GHz (10010-909 and 21010-20020 transitions) with beam sizes of 24'' and 18\arcsec, respectively. The detection of hyperfine structure in the 101-000 transition is consistent with optically thin emission under conditions of Local Thermodynamic Equilibrium (LTE). This is corroborated by a rotational diagram analysis of Orion-KL that indicates optically thin l...
![Research paper thumbnail of Submillimeter Array 12 CO ([FORMULA][F]J=3-2[/F][/FORMULA]) Interferometric Observations of the Central Region of M51](https://attachments.academia-assets.com/41248559/thumbnails/1.jpg)
](The Astrophysical Journal, 2004
We present the first interferometric 12 CO ( ) observations (beam size of or pc) with J p 3-2 3Љ ... more We present the first interferometric 12 CO ( ) observations (beam size of or pc) with J p 3-2 3Љ .9 # 1Љ .6 160 # 65 the Submillimeter Array (SMA) toward the center of the Seyfert 2 galaxy M51. The image shows a strong concentration at the nucleus and weak emission from the spiral arm to the northwest. The integrated intensity of the central component in 12 CO ( ) is almost twice as high as that in 12 CO ( ), indicating that the molecular gas within an J p 3-2 J p 1-0 ∼80 pc radius of the nucleus is warm (տ100 K) and dense (∼10 4 cm Ϫ3 ). Similar intensity ratios are seen in shocked regions in our Galaxy, suggesting that these gas properties may be related to active galactic nucleus or starburst activity. The central component shows a linear velocity gradient (∼1 . 4k ms Ϫ1 pc Ϫ1 ) perpendicular to the radio continuum jet, similar to that seen in previous observations and interpreted as a circumnuclear molecular disk/torus around the Seyfert 2 nucleus. In addition, we identify a linear velocity gradient (0.7 km s Ϫ1 pc Ϫ1 ) along the jet. Judging from the energetics, the velocity gradient can be explained by supernova explosions or energy and momentum transfer from the jet to the molecular gas via interaction, which is consistent with the high-intensity ratio.
Astronomy and Astrophysics, 2006
We observed a sample of 35 water masers not coincident with known HII regions and/or low mass you... more We observed a sample of 35 water masers not coincident with known HII regions and/or low mass young stellar objects (YSOs) with the Effelsberg 100 m telescope in the NH 3 (J, K) = (1, 1), (2, 2), (3, 3) and (4, 4) transitions. Sixteen sources were detected in the NH 3 emission. The detection rate is 46%. All these sixteen sources have NH 3 (1, 1) and (2, 2) emission, among which four sources have NH 3 (3, 3) emission. Comparing with the IRAS and the 2MASS data, we analyzed the relationship between the detection rate and the infrared color, the dust temperature and the source distance. All the detected sources were mapped and 17 cores were obtained (one source IRAS 20215+3725 has two cores). From the detected sources five cores do not coincide with radio continuum or IRAS and MSX point sources. Excluding one core that has no MSX data available, the remaining eleven cores are coincident with IRAS or MSX point sources. The typical size and mass of the cores are 1.6 pc and 1.5 × 10 3 M ⊙ , respectively. The average line widths of the NH 3 (1, 1) and (2, 2) are 1.54 and 1.73 km s −1 . The average kinetic temperature of the gas is about 19 K. These values are much larger than those of low mass cores. The NH 3 cores that coincide with IRAS sources (referred to as Group I) have slightly larger line widths (1.65 and 1.75 km s −1 for the (1, 1) and (2, 2) lines, respectively) and larger masses (1.8 × 10 3 M ⊙ ) than the mean values of the sample. For this type of core the kinetic temperature correlates with the line width. The line width appears to correlate with the bolometric luminosity and the core size. Despite the average luminosity of 2.9 × 10 4 L ⊙ , there is no detectable 6 cm emission. These are candidates for high mass protostars or precursors of UC HII regions. The NH 3 cores with peaks offset from infrared sources (referred to as Group II) have an average size of 1.7 pc and an average line width of 1.50 km s −1 for the (1, 1) line. The line width of the (1, 1) emission is smaller than that of the group I. The average mass is 9.4 × 10 2 M ⊙ . One possible explanation for the deviation is that the NH 3 peak and the infrared source correspond to different clumps. These cores are potential high mass star formation sites and may be at an earlier evolutionary stage than those with IRAS point sources. This type of core is seen in mapping observations, and can be easily missed by single-spectrum observations toward the IRAS position.
Astronomy and Astrophysics Supplement Series, 1998
Observations of H_2O maser sources on the 13.7 m radio telescope of Purple Mountain Observatory f... more Observations of H_2O maser sources on the 13.7 m radio telescope of Purple Mountain Observatory from 1990 Aug. to 1994 Jan. are summarized. For searching new water masers, the total number of search candidates is about 360, with 110 objects detected. Among them are 96 new detections. A list of the new detections and their spectra are presented. Table 1
Astronomy and Astrophysics, 2007
Aims. The high angular resolution images with the Very Large Array (VLA) allow us to explore the ... more Aims. The high angular resolution images with the Very Large Array (VLA) allow us to explore the general properties of protostellar cores in massive star forming regions at large distances. Methods. We observed the NH 3 (J, K) = (1, 1) and (2, 2) lines toward five massive protostar candidates (IRAS 18196-1331, IRAS 18352-0148, IRAS 18361-0627, IRAS 18414-0339 and IRAS 19474+2637) with the VLA D configuration. Results. We found that these objects have hundreds of solar masses in dense gas with rotation temperatures from 8 to 27 K. No 1.3 cm continuum emission was detected at an rms of ∼0.7 mJy in all sources except IRAS 18361-0627. We identified 60 clumps and determined their physical parameters (e.g. line width, rotation temperature, size, and mass). The clump masses range from 0.1 M ⊙ to 4800 M ⊙ . The average size, line width and temperature are 0.1 ± 0.06 pc, 1.3 ± 0.4 km s −1 and 16 ± 5 K. The discrepancy between NH 3 and (sub)mm continuum emission is found in IRAS 18196-1331. This phenomenon could occur as a result of the NH 3 abundance variation being affected by the UV illumination.
This paper describes observations of search for H2O masers using 13.7 m radio telescope in 1993. ... more This paper describes observations of search for H2O masers using 13.7 m radio telescope in 1993. The sources were selected on the basis of infrared observations of star masers at Xinlong Station, Beijing Astronomical Observatory.
Astronomy & Astrophysics - ASTRON ASTROPHYS, 2000
We surveyed 81 dense molecular cores associated with regions of massive star formation and Sgr A ... more We surveyed 81 dense molecular cores associated with regions of massive star formation and Sgr A in the JK-1K-1 = 505-404 and 10010-909 lines of HNCO. Line emission was detected towards 57 objects. Selected subsamples were also observed in the 101-000, 404-303, 707-606, 15015-14014, 16016-15015 and 21021-20020 lines, covering a frequency range from 22 to 461 GHz. HNCO lines from the K-1 = 2,3 ladders were detected in several sources. Towards Orion-KL, K-1 = 5 transitions with upper state energies Eu/k ~ 1100 and 1300 K could be observed. Five HNCO cores were mapped. The sources remain spatially unresolved at 220 and 461 GHz (10010-909 and 21010-20020 transitions) with beam sizes of 24'' and 18\arcsec, respectively. The detection of hyperfine structure in the 101-000 transition is consistent with optically thin emission under conditions of Local Thermodynamic Equilibrium (LTE). This is corroborated by a rotational diagram analysis of Orion-KL that indicates optically thin l...
The Astrophysical Journal, 2004
We present the first interferometric 12 CO ( ) observations (beam size of or pc) with J p 3-2 3Љ ... more We present the first interferometric 12 CO ( ) observations (beam size of or pc) with J p 3-2 3Љ .9 # 1Љ .6 160 # 65 the Submillimeter Array (SMA) toward the center of the Seyfert 2 galaxy M51. The image shows a strong concentration at the nucleus and weak emission from the spiral arm to the northwest. The integrated intensity of the central component in 12 CO ( ) is almost twice as high as that in 12 CO ( ), indicating that the molecular gas within an J p 3-2 J p 1-0 ∼80 pc radius of the nucleus is warm (տ100 K) and dense (∼10 4 cm Ϫ3 ). Similar intensity ratios are seen in shocked regions in our Galaxy, suggesting that these gas properties may be related to active galactic nucleus or starburst activity. The central component shows a linear velocity gradient (∼1 . 4k ms Ϫ1 pc Ϫ1 ) perpendicular to the radio continuum jet, similar to that seen in previous observations and interpreted as a circumnuclear molecular disk/torus around the Seyfert 2 nucleus. In addition, we identify a linear velocity gradient (0.7 km s Ϫ1 pc Ϫ1 ) along the jet. Judging from the energetics, the velocity gradient can be explained by supernova explosions or energy and momentum transfer from the jet to the molecular gas via interaction, which is consistent with the high-intensity ratio.
Astronomy and Astrophysics, 2006
We observed a sample of 35 water masers not coincident with known HII regions and/or low mass you... more We observed a sample of 35 water masers not coincident with known HII regions and/or low mass young stellar objects (YSOs) with the Effelsberg 100 m telescope in the NH 3 (J, K) = (1, 1), (2, 2), (3, 3) and (4, 4) transitions. Sixteen sources were detected in the NH 3 emission. The detection rate is 46%. All these sixteen sources have NH 3 (1, 1) and (2, 2) emission, among which four sources have NH 3 (3, 3) emission. Comparing with the IRAS and the 2MASS data, we analyzed the relationship between the detection rate and the infrared color, the dust temperature and the source distance. All the detected sources were mapped and 17 cores were obtained (one source IRAS 20215+3725 has two cores). From the detected sources five cores do not coincide with radio continuum or IRAS and MSX point sources. Excluding one core that has no MSX data available, the remaining eleven cores are coincident with IRAS or MSX point sources. The typical size and mass of the cores are 1.6 pc and 1.5 × 10 3 M ⊙ , respectively. The average line widths of the NH 3 (1, 1) and (2, 2) are 1.54 and 1.73 km s −1 . The average kinetic temperature of the gas is about 19 K. These values are much larger than those of low mass cores. The NH 3 cores that coincide with IRAS sources (referred to as Group I) have slightly larger line widths (1.65 and 1.75 km s −1 for the (1, 1) and (2, 2) lines, respectively) and larger masses (1.8 × 10 3 M ⊙ ) than the mean values of the sample. For this type of core the kinetic temperature correlates with the line width. The line width appears to correlate with the bolometric luminosity and the core size. Despite the average luminosity of 2.9 × 10 4 L ⊙ , there is no detectable 6 cm emission. These are candidates for high mass protostars or precursors of UC HII regions. The NH 3 cores with peaks offset from infrared sources (referred to as Group II) have an average size of 1.7 pc and an average line width of 1.50 km s −1 for the (1, 1) line. The line width of the (1, 1) emission is smaller than that of the group I. The average mass is 9.4 × 10 2 M ⊙ . One possible explanation for the deviation is that the NH 3 peak and the infrared source correspond to different clumps. These cores are potential high mass star formation sites and may be at an earlier evolutionary stage than those with IRAS point sources. This type of core is seen in mapping observations, and can be easily missed by single-spectrum observations toward the IRAS position.
Astronomy and Astrophysics Supplement Series, 1998
Observations of H_2O maser sources on the 13.7 m radio telescope of Purple Mountain Observatory f... more Observations of H_2O maser sources on the 13.7 m radio telescope of Purple Mountain Observatory from 1990 Aug. to 1994 Jan. are summarized. For searching new water masers, the total number of search candidates is about 360, with 110 objects detected. Among them are 96 new detections. A list of the new detections and their spectra are presented. Table 1