Report
CO Multi-line Imaging of Nearby Galaxies (COMING): I. Physical properties of molecular gas in the barred spiral galaxy NGC 2903
| العنوان: | CO Multi-line Imaging of Nearby Galaxies (COMING): I. Physical properties of molecular gas in the barred spiral galaxy NGC 2903 |
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| المؤلفون: | Muraoka, Kazuyuki, Sorai, Kazuo, Kuno, Nario, Nakai, Naomasa, Nakanishi, Hiroyuki, Takeda, Miho, Yanagitani, Kazuki, Kaneko, Hiroyuki, Miyamoto, Yusuke, Kishida, Nozomi, Hatakeyama, Takuya, Umei, Michiko, Tanaka, Takahiro, Tomiyasu, Yuto, Saita, Chey, Ueno, Saeko, Matsumoto, Naoko, Salak, Dragan, Morokuma-Matsui, Kana |
| سنة النشر: | 2016 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Astrophysics of Galaxies |
| الوصف: | We present simultaneous mappings of J=1-0 emission of 12CO, 13CO, and C18O molecules toward the whole disk (8' x 5' or 20.8 kpc x 13.0 kpc) of the nearby barred spiral galaxy NGC 2903 with the Nobeyama Radio Observatory 45-m telescope at an effective angular resolution of 20" (or 870 pc). We detected 12CO(J=1-0) emission over the disk of NGC 2903. In addition, significant 13CO(J=1-0) emission was found at the center and bar-ends, whereas we could not detect any significant C18O(J=1-0) emission. In order to improve the signal-to-noise ratio of CO emission and to obtain accurate line ratios of 12CO(J=2-1)/12CO(J=1-0) ($R_{2-1/1-0}$) and 13CO(J=1-0)/12CO(J=1-0) ($R_{13/12}$), we performed the stacking analysis for our 12CO(J=1-0), 13CO(J=1-0), and archival 12CO(J=2-1) spectra with velocity-axis alignment in nine representative regions of NGC 2903. We successfully obtained the stacked spectra of the three CO lines, and could measure averaged $R_{2-1/1-0}$ and $R_{13/12}$ with high significance for all the regions. We found that both $R_{2-1/1-0}$ and $R_{13/12}$ differ according to the regions, which reflects the difference in the physical properties of molecular gas; i.e., density ($n_{\rm H_2}$) and kinetic temperature ($T_K$). We determined $n_{\rm H_2}$ and $T_K$ using $R_{2-1/1-0}$ and $R_{13/12}$ based on the large velocity gradient approximation. The derived $n_{\rm H_2}$ ranges from ~ 1000 cm$^{-3}$ (in the bar, bar-ends, and spiral arms) to 3700 cm$^{-3}$ (at the center) and the derived $T_K$ ranges from 10 K (in the bar and spiral arms) to 30 K (at the center). We examined the dependence of star formation efficiencies (SFEs) on $n_{\rm H_2}$ and $T_K$, and found the positive correlation between SFE and $n_{\rm H_2}$ with the correlation coefficient for the least-square power-law fit $R^2$ of 0.50. This suggests that molecular gas density governs the spatial variations in SFEs. Comment: 26 pages, 11 figures, 3 tables, accepted for publication in PASJ |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1093/pasj/psw080 |
| URL الوصول: | http://arxiv.org/abs/1607.08023 |
| رقم الانضمام: | edsarx.1607.08023 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1093/pasj/psw080 |
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