We presented a multi-wavelength study of AFGL 333-Ridge. The molecular line data reveals that the AFGL 333-Ridge has two independent velocity components at -50.5 km/s and -48.0 km/s. In the Position-Velocity diagram, the bridge feature connects with two parts that are spatially correlated but separated in velocity. These observational evidences support the scenario that the two velocity components have collided and merged into one molecular cloud. The majority of Class I YSOs are distributed within the collision region, suggesting that the cloud-cloud collision has induced the YSOs formation in the ridge. Using the radio recombination line (RRL) data obtained by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), the RRL velocities of three HII regions are consistent with that of the AFGL 333-Ridge. By comparing the three HII regions' dynamical ages with the collision timescale of the two components, we conclude that the influence of the three HII regions may not drive the two clouds to merge. The formation of the AFGL 333-Ridge is probably due to the expansion of the giant HII region W4.
We present multi-wavelength data to investigate the physical properties and fragmentation of AFGL 333- Ridge. A statistical analysis of velocity dispersion indicates that turbulence is the dominant motion in the ridge. However, the linear mass density (1124.0 M/pc) of AFGL 333-Ridge far exceeds its critical value of 406.5 M/pc, suggesting that additional motions are required to prevent the filament radial collapse. Using the getsources algorithm, we identified 14 cores from the Herschel maps, including two protostellar cores and 12 starless cores. All of these starless cores are gravitationall…
We investigated the star formation activities in the AFGL333 region, which is in the vicinity of the W4 expanding bubble, by conducting NH3 (1,1), (2,2), and (3,3) mapping observations with the 45 m Nobeyama Radio Telescope at an angular resolution of 75". The morphology of the NH3 (1,1) map shows a bow-shape structure with the size of 2.0 x 0.6 pc as seen in the dust continuum. At the interface between the W4 bubble and the dense NH3 cloud, the compact HII region G134.2+0.8, associated with IRAS02245+6115, is located. Interestingly, just north and south of G134.2+0.8 we found NH3 emission exh…
This paper aims to investigate the hypothesis that the embedded luminous star AFGL2591-VLA3 (2.3E5Lsun at 3.33kpc) is forming according to a scaled-up version of a low-mass star formation scenario. We present multi-configuration VLA 3.6cm and 7mm, as well as CARMA C18O and 3mm continuum observations to investigate the morphology and kinematics of the ionized gas, dust, and molecular gas around AFGL2591. We also compare our results to ancillary near-IR images, and model the SED and 2MASS image profiles of AFGL2591 using a dust continuum radiative transfer code. The observed 3.6cm images uncover…
We have studied the dust density, temperature and velocity distributions of the archetypal massive young stellar object (MYSO) AFGL 2591. Given its high luminosity ($L=2 \times 10^5$ L$_\odot$) and distance ($d=3.3$ kpc), AFGL 2591 has one of the highest $\sqrt{L}/d$ ratio, giving better resolved dust emission than any other MYSO. As such, this paper provides a template on how to use resolved multi-wavelength data and radiative transfer to obtain a well-constrained 2-D axi-symmetric analytic rotating infall model. We show for the first time that the resolved dust continuum emission from Hersch…
We have observed the massive protostar AFGL 2136 IRS 1 in multiple wavelength windows in the near-to-mid-infrared at high ($\sim3$ km s$^{-1}$) spectral resolution using VLT+CRIRES, SOFIA+EXES, and Gemini North+TEXES. There is an abundance of H$_2$O absorption lines from the $ν_1$ and $ν_3$ vibrational bands at 2.7 $μ$m, from the $ν_2$ vibrational band at 6.1 $μ$m, and from pure rotational transitions near 10-13 $μ$m. Analysis of state-specific column densities derived from the resolved absorption features reveals that an isothermal absorbing slab model is incapable of explaining the relative …
We present the analysis of Spitzer/IRAC and NIR imaging observation of AFGL 5157, an active star forming region. In the IRAC images, this region shows strong PAH emissions in channel 4 and H$_2$ emissions in channel 2. Many of the H$_2$ features are aligned to form jet-like structures. Three bipolar jets in the NH$_3$ core region and a couple of jets northwest of the core have been identified. We identify the possible driving agents of the bipolar jets and show them to be very young. An embedded cluster has been detected in the NH$_3$ core; many members in the cluster show their SEDs increasin…
To probe the ongoing physical mechanism, we studied a wide-scale environment around AFGL 5142 (area ~25 pc x 20 pc) using a multi-wavelength approach. The Herschel column density (N(H_2)) map reveals a massive inverted Y-like structure (mass ~6280 M_sun), which hosts a pair of elongated filaments (lengths >10 pc). The Herschel temperature map depicts the filaments in a temperature range of ~12.5-13.5 K. These elongated filaments overlap each other at several places, where N(H_2) > 4.5 x 10^{21}cm^{-2}. The 12CO and 13CO line data also show two elongated cloud components (around -1.5 and -4.5 k…
We observationally investigate star formation (SF) process occurring in AFGL 5157 (area ~13.5 pc X 13.5 pc) using a multi-wavelength approach. Embedded filaments are seen in the {\it Herschel} column density map, and one of them is identified as an elongated filamentary feature (FF) (length ~8.3 pc; mass ~1170 Msun). Five Herschel clumps (Mclump ~45-300 Msun) are traced in the central part of FF, where an extended temperature structure (Td ~13.5-26.5 K) is observed. In the direction of the central part of FF, the warmer region at Td ~20-26.5 K spatially coincides with a mid-infrared (MIR) shel…
The Galactic center dust ridge consists of a narrow string of massive condensations identified in submillimeter dust continuum emission. To determine whether new high-mass stars are forming in this region, we performed new observations at 870 $μ$m with the Atacama Pathfinder Experiment telescope and at 8.4 GHz with the Very Large Array. We complement our data with recent maser and mid-infrared results. The ridge's clouds are dark at mid-infrared wavelengths, indicating the presence of cold, high column density material. In combination with existing temperature measurements in the dust ridge, w…
Increasing evidence suggests that, similar to their low-mass counterparts, high-mass stars form through a disk-mediated accretion process. At the same time, formation of high-mass stars still necessitates high accretion rates, and hence, high gas densities, which in turn can cause disks to become unstable against gravitational fragmentation. We study the kinematics and fragmentation of the disk around the high-mass star forming region AFGL 2591-VLA 3 which was hypothesized to be fragmenting based on the observations that show multiple outflow directions. We use a new set of high-resolution (0.…
Galaxy clusters are the most massive gravitationally bound structures in the Universe. They grow by accreting smaller structures in a merging process that produces shocks and turbulence in the intra-cluster gas. We observed a ridge of radio emission connecting the merging galaxy clusters Abell 0399 and Abell 0401 with the Low Frequency Array (LOFAR) at 140 MHz. This emission requires a population of relativistic electrons and a magnetic field located in a filament between the two galaxy clusters. We performed simulations to show that a volume-filling distribution of weak shocks may re-accelera…
Star formation within the Central Molecular Zone (CMZ) may be intimately linked to the orbital dynamics of the gas. Recent models suggest that star formation within the dust ridge molecular clouds (from G0.253+0.016 to Sgr B2) follows an evolutionary time sequence, triggered by tidal compression during their preceding pericentre passage. Given that these clouds are the most likely precursors to a generation of massive stars and extreme star clusters, this scenario would have profound implications for constraining the time-evolution of star formation. In this Letter, we search for the initial c…
The central molecular zone (CMZ) hosts some of the most massive and dense molecular clouds and star clusters in the Galaxy, offering an important window into star formation under extreme conditions. Star formation in this extreme environment may be closely linked to the 3-D distribution and orbital dynamics of the gas. Here I discuss how our new, accurate description of the $\{l,b,v\}$ structure of the CMZ is helping to constrain its 3-D geometry. I also present the discovery of a highly-regular, corrugated velocity field located just upstream from the dust ridge molecular clouds (which includ…
We review the use of young low mass stars and protostars, or young stellar objects (YSOs), as tracers of star formation. Observations of molecular clouds at visible, infrared, radio and X-ray wavelengths can identify and characterize the YSOs populating these clouds, with the ability to detect deeply embedded objects and all evolutionary stages. Surveys with the Spitzer, Herschel, XMM-Newton and Chandra space telescopes have measured the spatial distribution of YSOs within a number of nearby (< 2.5 kpc) molecular clouds, showing surface densities varying by more than three orders of magnitude.…
Protoplanetary disks in dense, massive star-forming regions are strongly affected by their environment. How this environmental impact changes over time is an important constraint on disk evolution and external photoevaporation models. We characterize the dust emission from 179 disks in the core of the young (0.5 Myr) NGC 2024 cluster. By studying how the disk mass varies within the cluster, and comparing these disks to those in other regions, we aim to determine how external photoevaporation influences disk properties over time. Using the Atacama Large Millimeter/submillimeter Array, a 2.9' x …
We present large-field (4.25~$\times$~3.75 deg$^2$) mapping observations toward the Galactic region centered at $l = 150\arcdeg, b = 3.5\arcdeg$ in the $J = 1-0$ emission line of CO isotopologues ($^{12}$CO, $^{13}$CO, and C$^{18}$O), using the 13.7 m millimeter-wavelength telescope of the Purple Mountain Observatory. Based on the $^{13}$CO observations, we reveal a filamentary cloud in the Local Arm at a velocity range of $-$0.5 to 6.5~km~s$^{-1}$. This molecular cloud contains 1 main filament and 11 sub-filaments, showing the so-called "ridge-nest" structure. The main filament and three sub-…
The RCW41 star-forming region is embedded within the Vela Molecular Ridge, hosting a massive stellar cluster surrounded by a conspicuous HII region. Understanding the role of interstellar magnetic fields and studying the newborn stellar population is crucial to build a consistent picture of the physical processes acting on this kind of environment. We have carried out a detailed study of the interstellar polarization toward RCW41, with data from an optical and near-infrared polarimetric survey. Additionally, deep near-infrared images from the NTT 3.5m telescope have been used to study the phot…
We study star formation in the Center Ridge 1 (CR1) clump in the Vela C giant molecular cloud, selected as a high column density region that shows the lowest level of dust continuum polarization angle dispersion, likely indicating that the magnetic field is relatively strong. We observe the source with the ALMA 7m-array at 1.05~mm and 1.3~mm wavelengths, which enable measurements of dust temperature, core mass and astrochemical deuteration. A relatively modest number of eleven dense cores are identified via their dust continuum emission, with masses spanning from 0.17 to 6.7 Msun. Overall CR1 …
This paper presents the observations of the Cloud D in the Vela Molecular Ridge, obtained with the IRAC camera onboard the Spitzer Space Telescope at the wavelengths λ= 3.6, 4.5, 5.8, 8.0 μm. A photometric catalog of point sources, covering a field of approximately 1.2 square degrees, has been extracted and complemented with additional available observational data in the millimeter region. Previous observations of the same region, obtained with the Spitzer MIPS camera in the photometric bands at 24 μm and 70 μm, have also been reconsidered to allow an estimate of the spectral slope of the sour…
Detailed studies of intermediate/low mass pre-main sequence (PMS) stars outside the Galaxy have so far been conducted only for small targeted regions harbouring known star formation complexes. The VISTA Survey of the Magellanic Clouds (VMC) provides an opportunity to study PMS populations down to solar masses on a galaxy-wide scale. Our goal is to use near-infrared data from the VMC survey to identify and characterise PMS populations down to ~1 M_sun across the Magellanic Clouds. We present our colour-magnitude diagram method, and apply it to a ~1.5 deg^2 pilot field located in the Large Magel…
