Abstract
To study the high-transition dense-gas tracers and their relationships to the star formation of the inner ∼2 kpc circumnuclear region of NGC 253, we present HCN J = 4−3 and HCO+ J = 4−3 maps obtained with the James Clerk Maxwell Telescope. Using the spatially resolved data, we compute the concentration indices r90/r50 for the different tracers. HCN and HCO+ 4-3 emission features tend to be centrally concentrated, which is in contrast to the shallower distribution of CO 1-0 and the stellar component. The dense-gas fraction (fdense, traced by the velocity-integrated-intensity ratios of HCN/CO and HCO+/CO) and the ratio R31 (CO 3-2/1-0) decline towards larger galactocentric distances, but increase with higher star formation rate surface density. The radial variation and the large scatter of fdense and R31 imply distinct physical conditions in different regions of the galactic disc. The relationships of fdense versus Σstellar, and SFEdense versus Σstellar are explored. SFEdense increases with higher Σstellar in this galaxy, which is inconsistent with previous work that used HCN 1-0 data. This implies that existing stellar components might have different effects on the high-J HCN and HCO+ than their low-J emission. We also find that SFEdense seems to be decreasing with higher fdense which is consistent with previous works, and it suggests that the ability of the dense gas to form stars diminishes when the average density of the gas increases. This is expected in a scenario where only the regions with high-density contrast collapse and form stars.
| Original language | English |
|---|---|
| Pages (from-to) | 1276-1296 |
| Number of pages | 21 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 494 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 2020 May 1 |
Bibliographical note
Funding Information:We thank the anonymous referee for the very helpful comments. We thank Antonio Usero for kindly providing the data used for Fig. 10. We also thank Padelis P. Papadopoulos for his contribution to the observing effort for the project and for providing helpful discussions and feedback on the draft. This research is supported by the National Key R&D Program of China with no. 2017YFA0402704, and no. 2016YFA0400702. It is also supported by the National Natural Science Foundation of China (grants nos. 11861131007, 11420101002, 11603075, 11721303, U1731237, 11933011 and 11673057), and Chinese Academy of Sciences Key Research Program of Frontier Sciences (grant no. QYZDJSSW-SLH008). MJM acknowledges the support of the National Science Centre, Poland through the grant 2018/30/E/ST9/00208. The research of CDW is supported by grants from the Natural Sciences and Engineering Research Council of Canada and the Canada Research Chairs program. JHH is supported by NSFC grant nos. 11873086 and U1631237, and by Yunnan Province of China (No. 2017HC018). SM is supported by the Ministry of Science and Technology (MOST) of Taiwan, MOST 107-2119-M-001-020. This work is sponsored (in part) by the Chinese Academy of Sciences (CAS), through a grant to the CAS South America Center for Astronomy (CASSACA) in Santiago, Chile. The James Clerk Maxwell Telescope is operated by the East Asian Observatory on behalf of The National Astronomical Observatory of Japan; Academia Sinica Institute of Astronomy and Astrophysics; the Korea Astronomy and Space Science Institute; Center for Astronomical Mega-Science (as well as the National Key R&D Program of China with no. 2017YFA0402700). Additional funding support is provided by the Science and Technology Facilities Council of the United Kingdom and participating universities in the United Kingdom and Canada.
Funding Information:
We thank the anonymous referee for the very helpful comments. We thank Antonio Usero for kindly providing the data used for Fig. 10. We also thank Padelis P. Papadopoulos for his contribution to the observing effort for the project and for providing helpful discussions and feedback on the draft. This research is supported by the National Key R&D Program of China with no. 2017YFA0402704, and no. 2016YFA0400702. It is also supported by the National Natural Science Foundation of China ( grants nos. 11861131007, 11420101002, 11603075, 11721303, U1731237, 11933011 and 11673057), and Chinese Academy of Sciences Key Research Program of Frontier Sciences (grant no. QYZDJ-SSW-SLH008). MJM acknowledges the support of the National Science Centre, Poland through the grant 2018/30/E/ST9/00208. The research of CDW is supported by grants from the Natural Sciences and Engineering Research Council of Canada and the Canada Research Chairs program. JHH is supported by NSFC grant nos. 11873086 and U1631237, and by Yunnan Province of China (No. 2017HC018). SM is supported by the Ministry of Science and Technology (MOST) of Taiwan, MOST 107-2119-M-001-020. This work is sponsored (in part) by the Chinese Academy of Sciences (CAS), through a grant to the CAS South America Center for Astronomy (CASSACA) in Santiago, Chile. The James Clerk Maxwell Telescope is operated by the East Asian Observatory on behalf of The National Astronomical Observatory of Japan; Academia Sinica Institute of Astronomy and Astrophysics; the Korea Astronomy and Space Science Institute; Center for Astronomical Mega-Science (as well as the National Key R&D Program of China with no. 2017YFA0402700). Additional funding support is provided by the Science and Technology Facilities Council of the United Kingdom and participating universities in the United Kingdom and Canada.
Publisher Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science