تقرير
Surveying the Whirlpool at Arcseconds with NOEMA (SWAN)- I. Mapping the HCN and N$_2$H$^+$ 3mm lines
| العنوان: | Surveying the Whirlpool at Arcseconds with NOEMA (SWAN)- I. Mapping the HCN and N$_2$H$^+$ 3mm lines |
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| المؤلفون: | Stuber, Sophia K., Pety, Jerome, Schinnerer, Eva, Bigiel, Frank, Usero, Antonio, Beslić, Ivana, Querejeta, Miguel, Jiménez-Donaire, María J., Leroy, Adam, Brok, Jakob den, Neumann, Lukas, Eibensteiner, Cosima, Teng, Yu-Hsuan, Barnes, Ashley, Chevance, Mélanie, Colombo, Dario, Dale, Daniel A., Glover, Simon C. O., Liu, Daizhong, Pan, Hsi-An |
| سنة النشر: | 2023 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Astrophysics of Galaxies |
| الوصف: | We present the first results from "Surveying the Whirlpool at Arcseconds with NOEMA" (SWAN), an IRAM Northern Extended Millimetre Array (NOEMA)+30m large program that maps emission from several molecular lines at 90 and 110 GHz in the iconic nearby grand-design spiral galaxy M~51 at cloud-scale resolution ($\sim$3\arcsec=125\,pc). As part of this work, we have obtained the first sensitive cloud-scale map of N$_2$H$^+$(1-0) of the inner $\sim5\,\times 7\,$kpc of a normal star-forming galaxy, which we compare to HCN(1-0) and CO(1-0) emission to test their ability in tracing dense, star-forming gas. The average N$_2$H$^+$-to-HCN line ratio of our total FoV is $0.20\pm0.09$, with strong regional variations of a factor of $\gtrsim 2$ throughout the disk, including the south-western spiral arm and the center. The central $\sim1\,$kpc exhibits elevated HCN emission compared to N$_2$H$^+$, probably caused by AGN-driven excitation effects. We find that HCN and N$_2$H$^+$ are strongly super-linearily correlated in intensity ($\rho_\mathrm{Sp}\sim 0.8$), with an average scatter of $\sim0.14\,$dex over a span of $\gtrsim 1.5\,$dex in intensity. When excluding the central region, the data is best described by a power-law of exponent $1.2$, indicating that there is more N$_2$H$^+$ per unit HCN in brighter regions. Our observations demonstrate that the HCN-to-CO line ratio is a sensitive tracer of gas density in agreement with findings of recent Galactic studies which utilize N$_2$H$^+$. The peculiar line ratios present near the AGN and the scatter of the power-law fit in the disk suggest that in addition to a first-order correlation with gas density, second-order physics (such as optical depth, gas temperature) or chemistry (abundance variations) are encoded in the N$_2$H$^+$/CO, HCN/CO and N$_2$H$^+$/HCN ratios. Comment: Accepted for publication in A&A. 6 pages, 3 figures (+ Appendix 4 pages, 2 figures) |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1051/0004-6361/202348205 |
| URL الوصول: | http://arxiv.org/abs/2312.09810 |
| رقم الأكسشن: | edsarx.2312.09810 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1051/0004-6361/202348205 |
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