Star formation rates in the L 1482 filament of the California molecular cloud

• Published in: Publications of the Astronomical Society of Japan Vol. 72; no. 4
• Main Authors: Omodaka, Toshihiro, Nagayama, Takumi, Dobashi, Kazuhito, Chibueze, James O, Yamabi, Akifumi, Shimajiri, Yoshito, Inoue, Shinnosuke, Hamada, Shota, Sunada, Kazuyoshi, Ueno, Yuji
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.08.2020
• Subjects: stars: formation; stars: individual (LkHα 101); ISM: clouds; masers; astrometry
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/psaa048

Abstract We measured the trigonometric parallax of the H2O maser source associated with the L 1482 molecular filament hosting the most massive young star, LkHα 101, in the California molecular cloud. The measured parallax is 1.879 ± 0.096 mas, corresponding to the distance of 532 ± 28 pc. This parallax is consistent with that of the nearby star cluster LkHα 101, which was recently measured with Gaia DR2. We found that the L 1482 molecular filament and the LkHα 101 cluster are located at the same distance within 3 ± 30 pc. We observed the southern parts of L 1482 molecular clouds including the H2O maser source, which is adjacent to LkHα 101, using the Nobeyama 45 m telescope in the J = 1–0 transitions of both 12CO and 13CO. The peak intensity of the 12CO line revealed the high excitation temperature region (60–70 K) due to heating by UV radiation from LkHα 101. We derived the column density of these molecular clouds assuming local thermodynamic equilibrium (LTE) from the 13CO emission. Using Dendrogam, we searched for small-scale, dense structures (cores) and identified 337 cores in the 13CO data. Gravitationally bound cores with a virial mass to LTE mass ratio ≤1.5 and young stars are concentrated in the high excitation temperature region. The column density in the warm region is five to six times larger than that of the surrounding colder molecular region. This suggests that the warm region has been compressed by a high-pressure wave and successive radiation-driven star formation is in progress in this warm region. In the cold molecular cloud to the north of the warm region, the cores are likely gravitationally unbound, which may be the reason why star formation is not active there.