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We present new observations of all three ground-state transitions of the methylidyne (CH) radical and all four ground-state transitions of the hydroxyl (OH) radical toward a sharp boundary region of the Taurus molecular cloud. These data…

星系天体物理 · 物理学 2016-12-12 Duo Xu , Di Li

A growing body of evidence has been supporting the existence of so-called "dark molecular gas" (DMG), which is invisible in the most common tracer of molecular gas, i.e., CO rotational emission. DMG is believed to be the main gas component…

星系天体物理 · 物理学 2015-03-10 Di Li , Duo Xu , Carl Heiles , Zhichen Pan , Ningyu Tang

We study four lines of sight that probe the transition from diffuse molecular gas to molecular cloud material in Taurus. Measurements of atomic and molecular absorption are used to infer the distribution of species and the physical…

Hydroxyl (OH) is expected to be abundant in diffuse interstellar molecular gas as it forms along with $H_2$ under similar conditions and within a similar extinction range. We have analyzed absorption measurements of OH at 1665 MHz and 1667…

We report the results from a new, highly sensitive ($\Delta T_{mb} \sim 3 $mK) survey for thermal OH emission at 1665 and 1667 MHz over a dense, 9 x 9-pixel grid covering a $1\deg$ x $1\deg$ patch of sky in the direction of $l = 105\deg, b…

When modeling infrared or gamma-ray data as a linear combination of observed gas tracers, excess emission has been detected compared to expectations from known neutral and atomic gas as traced by HI and CO measurements, respectively. This…

星系天体物理 · 物理学 2017-02-22 D. Paradis , K. Dobashi , T. Shimoikura , A. Kawamura , T. Onishi , Y. Fukui , J. -P. Bernard

The CO-dark molecular gas (DMG), which refers to the molecular gas not traced by CO emission, is crucial for the evolution of the interstellar medium (ISM). While the gas properties of DMG have been widely explored in the Solar…

星系天体物理 · 物理学 2024-05-22 Gan Luo , Di Li , Zhi-yu Zhang , Thomas G. Bisbas , Ningyu Tang , Lingrui Lin , Yichen Sun , Pei Zuo , Jing Zhou

Studying the atomic-to-molecular transition is essential for understanding the evolution of interstellar medium. The linear edge of Taurus molecular cloud, clearly identified in the $^{13}$CO(1-0) intensity map, serves as an ideal site for…

星系天体物理 · 物理学 2025-04-03 Ningyu Tang , Feihang Miao , Gan Luo , Di Li , Junzhi Wang , Fujun Du , Donghong Wu , Shu Liu

Neither HI nor CO emission can reveal a significant quantity of so-called dark gas in the interstellar medium (ISM). It is considered that CO-dark molecular gas (DMG), the molecular gas with no or weak CO emission, dominates dark gas. We…

星系天体物理 · 物理学 2016-09-14 Ningyu Tang , Di Li , Carl Heiles , Shen Wang , Zhichen Pan , Jun-Jie Wang

We present a study of the three-dimensional (3D) distribution of interstellar dust derived from stellar extinction observations toward the Taurus molecular cloud (MC) and its relation with the neutral atomic hydrogen (HI) emission at 21 cm…

(abridged) We report a study of the relation between dust and gas over a 100deg^2 area in the Taurus molecular cloud. We compare the H2 column density derived from dust extinction with the CO column density derived from the 12CO and 13CO J=…

We report here our latest search for molecular outflows from young brown dwarfs and very low-mass stars in nearby star-forming regions. We have observed three sources in Taurus with the Submillimeter Array and the Combined Array for…

太阳与恒星天体物理 · 物理学 2015-06-22 Ngoc Phan-Bao , Chin-Fei Lee , Paul T. P. Ho , Cuong Dang-Duc , Di Li

The most extensive survey of carbon monoxide (CO) gas in the Taurus molecular cloud relied on $^{12}$CO and $^{13}$CO $J=1 \rightarrow 0$ emission only, distinguishing the region where $^{12}$CO is detected without $^{13}$CO (named mask 1…

星系天体物理 · 物理学 2023-08-02 Yan Duan , Di Li , Laurent Pagani , Paul F. Goldsmith , Tao-Chung Ching , Chen Wang , Jinjin Xie

We present the first results on the diffuse transition clouds observed in [CII] line emission at 158 microns (1.9 THz) towards Galactic longitudes near 340deg (5 LOSs) and 20deg (11 LOSs) as part of the GOT C+ survey. Out of the total 146…

星系天体物理 · 物理学 2015-05-19 T. Velusamy , W. D. Langer , J. L. Pineda , P. F. Goldsmith , D. Li. , H. W. Yorke

We have obtained OH spectra of four transitions in the $^2\Pi_{3/2}$ ground state, at 1612, 1665, 1667, and 1720 MHz, toward 51 sightlines that were observed in the Herschel project Galactic Observations of Terahertz C+. The observations…

The mass of molecular gas in an interstellar cloud is often measured using line emission from low rotational levels of CO, which are sensitive to the CO mass, and then scaling to the assumed molecular hydrogen H_2 mass. However, a…

星系天体物理 · 物理学 2015-05-18 Mark G. Wolfire , David Hollenbach , Christopher F. McKee

We have conducted OH 18 cm survey toward 141 molecular clouds in various environments, including 33 optical dark clouds, 98 Planck Galactic cold clumps (PGCCs) and 10 Spitzer dark clouds with the Arecibo telescope. The deviations from local…

星系天体物理 · 物理学 2020-12-23 Ningyu Tang , Di Li , Nannan Yue , Pei Zuo , Tie Liu , Gan Luo , Longfei Chen , Sheng-Li Qin , Yuefang Wu , Carl Heiles

We report the results of a 100 square degree survey of the Taurus Molecular Cloud region in the J = 1-0 transition of 12CO and 13CO. The image of the cloud in each velocity channel includes ~ 3 million Nyquist sampled pixels on a 20" grid.…

天体物理学 · 物理学 2009-12-08 Paul F. Goldsmith , Mark Heyer , Gopal Narayanan , Ronald Snell , Di Li , Chris Brunt

The most abundant interstellar molecule, molecular Hydrogen (H$_{2}$), is practically invisible in cold molecular clouds. Astronomers typically use carbon monoxide (CO) to trace the bulk distribution and mass of H$_{2}$ in our galaxy and…

星系天体物理 · 物理学 2023-11-23 Michael P. Busch

A deep, wide-field, near-infrared imaging survey was used to construct an extinction map of the southeastern part of the California Molecular Cloud (CMC) with $\sim$ 0.5 arc min resolution. The same region was also surveyed in the…

星系天体物理 · 物理学 2015-05-27 S. Kong , C. J. Lada , E. A. Lada , C. Román-Zúñiga , J. H. Bieging , M. Lombardi , J. Forbrich , J. F. Alves
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