학술논문
FAUST VI. VLA 1623--2417 B: a new laboratory for astrochemistry around protostars on 50 au scale
Document Type
Working Paper
Author
Codella, C.; López-Sepulcre, A.; Ohashi, S.; Chandler, C. J.; De Simone, M.; Podio, L.; Ceccarelli, C.; Sakai, N.; Alves, F.; Durán, A.; Fedele, D.; Loinard, L.; Mercimek, S.; Murillo, N.; Bianchi, E.; Bouvier, M.; Busquet, G.; Caselli, P.; Dulieu, F.; Feng, S.; Hanawa, T.; Johnstone, D.; Lefloch, B.; Maud, L. T.; Moellenbrock, G.; Oya, Y.; Svoboda, B.; Yamamoto, S.
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Subject
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Abstract
The ALMA interferometer, with its unprecedented combination of high-sensitivity and high-angular resolution, allows for (sub-)mm wavelength mapping of protostellar systems at Solar System scales. Astrochemistry has benefited from imaging interstellar complex organic molecules in these jet-disk systems. Here we report the first detection of methanol (CH3OH) and methyl formate (HCOOCH3) emission towards the triple protostellar system VLA1623-2417 A1+A2+B, obtained in the context of the ALMA Large Program FAUST. Compact methanol emission is detected in lines from Eu = 45 K up to 61 K and 537 K towards components A1 and B, respectively. LVG analysis of the CH3OH lines towards VLA1623-2417 B indicates a size of 0.11-0.34 arcsec (14-45 au), a column density N(CH3OH) = 10^16-10^17 cm-2, kinetic temperature > 170 K, and volume density > 10^8 cm-3. An LTE approach is used for VLA1623-2417 A1, given the limited Eu range, and yields Trot < 135 K. The methanol emission around both VLA1623-2417 A1 and B shows velocity gradients along the main axis of each disk. Although the axial geometry of the two disks is similar, the observed velocity gradients are reversed. The CH3OH spectra from B shows two broad (4-5 km s-1) peaks, which are red- and blue-shifted by about 6-7 km s-1 from the systemic velocity. Assuming a chemically enriched ring within the accretion disk, close to the centrifugal barrier, its radius is calculated to be 33 au. The methanol spectra towards A1 are somewhat narrower (about 4 km s-1), implying a radius of 12-24 au.
Comment: MNRAS, in press
Comment: MNRAS, in press