We present observations of continuum emission in the MIR to mm wavelength range, complemented with ammonia observations, of the dense core ahead of the radio Herbig Haro object HH 80N, found in the GGD 27 region. The continuum emission in all the observed bands peaks at the same position, consistent with the presence of an embedded object, HH 80N-IRS1, within the core. The distribution of the VLA ammonia emission is well correlated with that of the dust, suggesting that photochemical effects caused by the nearby Herbig Haro object do not play an important role in shaping this particular molecular emission. In order to unveil the nature of HH 80N-IRS1 we analyzed the continuum data of this source, using self-consistent models of protostellar collapse. We find that a young protostar surrounded by a slowly rotating collapsing envelope of radius $\sim$0.08 pc and 20 \msun\ plus a circumstellar disk of radius $\sim$300 AU and 0.6 \msun\ provide a good fit to the observed spectral energy distribution and to the maps at 350 \micron, 1.2 mm and 3.5 mm of HH 80N-IRS1. Besides, the APEX and PdBI continuum maps at 350 \micron\ and 3.5 mm, respectively, reveal additional clumps in the continuum emission. Given the modeling results and the observed morphology of the emission, we propose a scenario consisting of a central embedded Class 0 object, HH 80N-IRS1, with the rest of material of the HH 80N core possibly undergoing fragmentation that may lead to the formation of several protostars
We present a Berkeley-Illinois-Maryland Association (BIMA) Array molecular survey of the star forming core ahead of HH 80N, the optically obscured northern counterpart of the Herbig-Haro objects HH 80/81. Continuum emission at 1.4 mm and 8 micron is detected at the center of the core, which confirms the presence of an embedded very young stellar object in the core. All detected molecular species arise in a ring-like structure, which is most clearly traced by CS(2-1) emission. This molecular ring suggests that strong molecular depletion occurs in the inner part of the core (at a radius of ~0.1 …
We present VLA NH3 and PdBI NH2D and H13NC observations of the star forming core ahead of HH 80N, the optically obscured northern counterpart of the Herbig-Haro objects HH 80/81. The main goal is to determine the kinematical information of the high density regions of the core ($n\lesssim 10^5$ cm$^{-3}$), missed in previous works due to the depletion of the species observed (e.g. CS). The obtained maps show different kinematical signatures between the eastern and western parts of the core, suggesting a possible dynamical interaction of the core with the HH 80/81/80N outflow. The analysis of th…
V2129 Oph is a 1.35 solar mass classical T Tauri star, known to possess a strong and complex magnetic field. By extrapolating from an observationally derived magnetic surface map, obtained through Zeeman-Doppler imaging, models of V2129 Oph's corona have been constructed, and used to make predictions regarding the global X-ray emission measure, the amount of modulation of X-ray emission, and the density of accretion shocks. In late June 2009 we will under take an ambitious multi-wavelength, multi-observing site, and near contemporaneous campaign, combining spectroscopic optical, nIR, UV, X-ray…
Our understanding of protoplanetary disks has greatly improved over the last decade due to a wealth of data from new facilities. Unbiased dust surveys with Spitzer leave us with good constraints on the dust dispersal timescale of small grains in the terrestrial planet forming region. In the ALMA era, this can be confronted for the first time also with evolutionary timescales of mm grains in the outer disk. Gas surveys in the context of the existing multi-wavelength dust surveys will be a key in large statistical studies of disk gas evolution. Unbiased gas surveys are limited to ALMA CO submm s…
We observed a field of $16'\times 16'$ in the star-forming region Pelican Nebula (IC 5070) at $BVRI$ wavelengths for 90 nights spread over one year in 2012-2013. More than 250 epochs in $VRI$-bands are used to identify and classify variables up to $V\sim 21$~mag. We present a catalogue of optical time-series photometry with periods, mean-magnitudes and classifications for 95 variable stars including 67 pre-main-sequence variables towards star-forming region IC 5070. The pre-main-sequence variables are further classified as candidate classical T Tauri and weak-line T Tauri stars based on their …
The brown dwarf population in the canonical star forming region NGC2264 is so far poorly explored. We present a deep, multi-wavelength, multi-epoch survey of the star forming cluster NGC2264, aimed to identify young brown dwarf candidates in this region. Using criteria including optical/near-infrared colours, variability, Spitzer mid-infrared colour excess, extinction, and Gaia parallax and proper motion (in order of relevance), we select 902 faint red sources with indicators of youth. Within this sample we identify 429 brown dwarf candidates based on their infrared colours. The brown dwarf ca…
In this paper, we present a detailed morphological, kinematic, and thermal analysis of two homologous magnetic flux ropes (MFRs) from NOAA 11515 on 2012 July 8--9. The study is based on multi-wavelength and dual-perspective imaging observations from the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory Ahead spacecraft, which can well reveal the structure and evolution of the two MFRs. We find that both of the MFRs show up in multiple passbands and their emissions mainly consist of a cold component peaking at a temperature of $\sim$0.4--0.6 MK and a hot component peaki…
Modeling the Far-Infrared Polarization Spectrum of a High-Mass Star Forming Cloud
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA)（天体物理学跨学科探索与研究中心）；Northwestern University（西北大学）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；Villanova University（维拉诺瓦大学）；SOFIA Science Center, NASA Ames Research Center（索菲亚科学中心，NASA艾姆斯研究中心）；University of Chicago（芝加哥大学）；Department of Astronomy, University of Virginia（弗吉尼亚大学天文学系）
Most stars and thus most planetary systems do not form in isolation. The larger star-forming environment affects protoplanetary disks in multiple ways: gravitational interactions with other stars truncate disks and alter the architectures of exoplanet systems; external irradiation from nearby high-mass stars truncates disks and shortens their lifetimes; and remaining gas and dust in the environment affects dynamical evolution (if removed by feedback processes) and provides some shielding for disks from external irradiation. The dynamical evolution of the region regulates when and how long vari…
High angular resolution observations of discs at mm wavelengths (on scales of a few au) are now commonplace, but there is a current lack of a comparable angular resolution for observations at cm wavelengths. This presents a significant barrier to improving our understanding of planet formation, in particular how dust grains grow from mm to cm sizes. In this paper, we examine the ability of the Square Kilometre Array (SKA) to observe dust substructure in a young, planet-forming disc at cm wavelengths. We use dusty hydrodynamics and continuum radiative transfer to predict the distribution and em…
The determination of chemical composition is crucial for investigating the formation and evolution of star forming galaxies and provides a powerful tool to constrain the effects of galactic winds and accretion from the cosmic web. In this regard stellar absorption line studies provide an attractive alternative to the standard techniques using the strong emission lines of HII regions. We discuss a number of newly developed methods: - multi-object spectroscopy of individual blue and red supergiant stars, the brightest stars in the universe at visual and NIR wavelengths, - NIR spectroscopy of sup…
Far-infrared and (sub)millimeter fluxes can be used to study dust in protoplanetary disks, the building blocks of planets. Here, we combine observations from the Herschel Space Observatory with ancillary data of 284 protoplanetary disks in the Taurus, Chamaeleon I, and Ophiuchus star-forming regions, covering from the optical to mm/cm wavelengths. We analyze their spectral indices as a function of wavelength and determine their (sub)millimeter slopes when possible. Most disks display observational evidence of grain growth, in agreement with previous studies. No correlation is found between oth…
We present new measurements of the dust emissivity index, beta, for the high-mass, star-forming OMC 2/3 filament. We combine 160-500 um data from Herschel with long-wavelength observations at 2 mm and fit the spectral energy distributions across a ~ 2 pc long, continuous section of OMC 2/3 at 15000 AU (0.08 pc) resolution. With these data, we measure beta and reconstruct simultaneously the filtered-out large-scale emission at 2 mm. We implement both variable and fixed values of beta, finding that beta = 1.7 - 1.8 provides the best fit across most of OMC 2/3. These beta values are consistent wi…
The high rate of planet detection among solar-type stars argues that planet formation is common. It is also generally assumed that planets form in protoplanetary discs like those observed in nearby star forming regions. On what timescale does the transformation from discs to planets occur? Here we show that current inventories of planets and protoplanetary discs are sensitive enough to place basic constraints on the timescale and efficiency of the planet formation process. A comparison of planet detection statistics and the measured solid reservoirs in T Tauri discs suggests that planet format…
We summarize the results of our long-running campaign to help understand the nature of high-mass X-ray binaries (HMXBs), emphasizing recent Suzaku observations of IGR J16207-5129 and IGR J17391-3021. Thanks to the expanding ranks of HMXBs in our Galaxy, we are able to perform more reliable statistical analyses on the three currently-known sub-classes of HMXB: those with supergiant companions (SGXBs); those with Be companions (BEXBs); and the enigmatic Supergiant Fast X-ray Transients (SFXTs). We discuss new diagnostic tools, akin to the "Corbet diagram," in which HMXBs tend to segregate based …
We investigate the influence of Wolf-Rayet (W-R) stars on their surrounding star-forming molecular clouds. We study five regions containing W-R stars in the inner Galactic plane ($l\sim$[14$^\circ$-52$^\circ$]), using multi-wavelength data from near-infrared to radio wavelengths. Analysis of $^{13}$CO line data reveals that these W-R stars have developed gas-deficient cavities in addition to molecular shells with expansion velocities of a few km s$^{-1}$. The pressure owing to stellar winds primarily drives these expanding shells and sweeps up the surrounding matter to distances of a few pc. T…
The majority of the ultimate main-sequence mass of a star is assembled in the protostellar phase, where a forming star is embedded in an infalling envelope and encircled by a protoplanetary disk. Studying mass accretion in protostars is thus a key to understanding how stars gain their mass and ultimately how their disks and planets form and evolve. At this early stage, the dense envelope reprocesses most of the luminosity generated by accretion to far-infrared and submillimeter wavelengths. Time-domain photometry at these wavelengths is needed to probe the physics of accretion onto protostars,…
The magnetic field plays an important role in every stage of the star-formation process from the collapse of the initial protostellar core to the star's arrival on the main sequence. Consequently, the goal of this science case is to explore a wide range of magnetic phenomena that can be investigated using the polarization capabilities of the Next Generation Very Large Array (ngVLA). These include (1) magnetic fields in protostellar cores via polarized emission from aligned dust grains, including in regions optically thick at wavelengths observable by the Atacama Large Millimeter/submillimeter …
The Rosetta Stone Project. II. The correlation between star formation efficiency and L/M indicator for the evolutionary stages of star-forming clumps in post-processed radiative magnetohydrodynamics simulations
本研究通过 Rosetta Stone 框架对恒星形成团块的辐射磁流体动力学模拟进行辐射转移后处理与合成观测，标定了 $L/M$ 指标与恒星形成效率之间的幂律相关性，为团块演化阶段分类提供了可靠依据。
