J. S. Zhang
Articles written in Journal of Astrophysics and Astronomy
Volume 32 Issue 1-2 March 2011 pp 37-41
H2O maser emissions have been found in external galaxies for more than 30 years. Main sciences associated with extragalactic H2O masers can be summarized roughly into three parts: maser emission itself, AGN sciences and cosmology exploration. Our work in this field focusses on two projects: X-ray data analysis of individual maser source using X-ray penetrability to explore maser host obscured AGN; multi-wavelength statistical properties of the whole published H2O maser sample. Here their nuclear radio properties were investigated in detail, based on their 6-cm and 20-cm radio observation data. Comparing the radio properties between maser-detected sources and non-detected sources at similar distance scale, we find that: (1) maser host galaxies tend to have higher nuclear radio luminosity; (2) the spectral index of both samples is comparable (∼ 0.6), within the error ranges. In addition, for AGN-maser sources, the isotropic maser luminosity tends to increase with rising radio luminosity. Thus we propose the nuclear radio luminosity as one good indicator for searching AGN-masers in the future.
Volume 32 Issue 1-2 March 2011 pp 49-51 Part 1. Blazar Observations in Radio
The Eddington ratio 𝜆 was derived for the entire maser host AGN sample, based on the intrinsic X-ray luminosity, the X-ray bolometric correction 𝐶X and the mass of central black hole. Further the [O III] bolometric correction 𝐶[O III] was estimated for our sample. Possible relations were also investigated between the maser luminosity and the bolometric luminosity – the Eddington ratio.
Volume 32 Issue 1-2 March 2011 pp 179-182 Part 3. Blazar Observations in High Energy Bands
For H2O megamaser galaxy Mrk 266, its Chandra and XMM–Newton data are analyzed here. It shows existence of two obscured nuclei (separation is ∼ 5''). Our preferred model, the high energy reflected model can fit the hard component of both nuclei spectra well.
Volume 32 Issue 1-2 March 2011 pp 331-332 Part 7. Other Topics
Astronomy is a very interesting subject for undergraduate students studying physics. In this paper, we report astronomy education for undergraduate students in the Physics Department of Guangzhou University, and how we are teaching astronomy to the students. Astrophysics has been rapidly developing since 1994, when the center for astrophysics was founded. Now, astrophysics has become a key subject in Guangdong Province, and the Astronomy Science and Technology Research Laboratory one of the key laboratories of the Department of Education of the Guangdong Province. Many undergraduate students, working under the tutorship of faculty members completed their thesis at the Center for Astrophysics in Guangzhou.
Volume 35 Issue 3 September 2014 pp 219-222 Part I: Blazar Observations in Radio
FAST, the Five-hundred meter Aperture Spherical radio Telescope, will become the largest operating single-dish telescope in the coming years. It has many advantages: much better sensitivity for its largest collecting area; large sky coverage due to its innovative design of the active primary surface; extremely radio quiet from its unique location, etc. In this work, I will highlight the future capabilities of FAST to discover and observe both galactic and extragalactic masers.
Volume 35 Issue 3 September 2014 pp 223-225 Posters
For the H2O maser host AGN sample, we derived their bolometric luminosity corrections, based on their X-ray data and [O III] emission line luminosities. Our results for maser AGNs is comparable to that of non-maser AGNs.
Volume 35 Issue 3 September 2014 pp 297-299 Posters
The infrared properties of Fermi AGNs were investigated using the survey data of the Wide-field Infrared Survey Explorer (WISE). The results showed:
BL Lacs tend to be brighter than FSRQs at 3.4 𝜇m. However, with increase of wavelength, FSRQs tend to be brighter than BL Lacs.
FSRQs colours are redder than BL Lacs;
A strong correlation exists between infrared and 𝛾-ray luminosity.
Volume 35 Issue 3 September 2014 pp 495-496 Part VII: Other Topics
We report the possible accretion from companion in the massive star forming region (G350.69–0.49). This region seems to be a binary system composed of a diffuse object (possible nebulae or UC HII region) and a Massive Young Stellar Object (MYSO) seen in Spitzer IRAC image. The diffuse object and MYSO are connected by the shock-excited 4.5 𝜇m emission, suggesting that the massive star may form through accreting material from the companion in this system.
Volume 35 Issue 3 September 2014 pp 509-511 Part VII: Other Topics
Extragalactic H2O masers have been found in dense gas circumstance in off-nuclear star formation regions or within parsecs of Active Galactic Nuclei (AGNs). HCN molecular (one of the best dense gas tracers) Emission has been detected in more than 60 galaxies. For HCN-detected galaxy sample, the relation of maser and gas emission was investigated here to identify physical observable properties that differentiate maser and non-maser galaxies. Our analysis results show that there is no significant difference on the infrared and gas emission between maser galaxies and galaxies without maser detection. For maser host HCN-galaxies, maser luminosity is found to be correlated to CO luminosity (a proxy of the total molecular gas) and HCN luminosity, i.e., kilomasers (𝐿H2O < 10𝐿⊙) with low maser luminosity having low gas emission luminosity, with respect to megamasers (𝐿H2O > 10𝐿⊙). For normalized maser and HCN luminosity (for removing distance effect), the correlation is still apparent. However, for normalized maser and CO luminosity, the correlation disappeared completely. Thus one proposition that the amount of dense molecular gas should be a good tracer of H2O maser emission can be made.
Volume 35 Issue 3 September 2014 pp 541-543 Part VII: Other Topics
We present our observations toward Sgr B2 region in 𝐽 = 1−0 lines of 12CO, 13CO, C18O and C17O using 13.7-m Delingha millimeter telescope with newly installed 9-beam SIS superconducting receiver. From the integrated line intensity, we derive the abundance ratio of C18O/C17O with a mean value of 3.11 ± 0.10, which is consistent with the previous results.
Volume 35 Issue 3 September 2014 pp 545-548 Part VII: Other Topics
For H2O megamaser galaxy Mrk 348, Chandra and XMM–Newton data are analysed. The nuclear fitting results of XMM–Newton data suggest the possible existence of a heavily obscured AGN. But the nuclear spectrum extracted from Chandra cannot be well-fitted by the best fitting model for XMM–Newton. Further optimal fitting and discussions are needed.
Volume 40 | Issue 6
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