To probe the star formation (SF) process, we present a multi-wavelength study of IRAS 05480+2545 (hereafter I05480+2545). Analysis of Herschel data reveals a massive clump (Mclump ∼ 1875 peak N(H2) ∼ ...4.8 × 1022 cm−2; AV ∼ 51 mag) containing the 6.7 GHz methanol maser and I05480+2545, which is also depicted in a temperature range of 18-26 K. Several noticeable parsec-scale filaments are detected in the Herschel 250 m image and seem to be radially directed to the massive clump. It resembles more of a "hub-filament" system. Deeply embedded young stellar objects (YSOs) have been identified using the 1-5 m photometric data, and a significant fraction of YSOs and their clustering are spatially found toward the massive clump, revealing the intense SF activities. An infrared counterpart (IRc) of the maser is investigated in the Spitzer 3.6-4.5 m images. The IRc does not appear as a point-like source and is most likely associated with the molecular outflow. Based on the 1.4 GHz and H continuum images, the ionized emission is absent toward the IRc, indicating that the massive clump harbors an early phase of a massive protostar before the onset of an ultracompact H ii region. Together, the I05480+2545 is embedded in a very similar "hub-filament" system to those seen in the Rosette Molecular Cloud. The outcome of the present work indicates the role of filaments in the formation of the massive star-forming clump and cluster of YSOs, which might help channel material to the central hub configuration and the clump/core.
ABSTRACT
We present a multiwavelength investigation of a large-scale physical system containing the W33 complex. The extended system (∼50 pc × 37 pc) is selected based on the distribution of ...molecular gas at 29.6, 60.2 km s−1 and of 88 ATLASGAL 870-μm dust clumps at d ∼2.6 kpc. The extended system/molecular cloud traced in the maps of 13CO and C18O emission contains several H ii regions excited by OB stars (age ∼0.3–1.0 Myr) and a thermally supercritical filament (fs1, length ∼17 pc). The filament, which is devoid of ionized gas, shows a dust temperature (Td) of ∼19 K, while the H ii regions have a Td of ∼21–29 K. It suggests the existence of two distinct environments in the cloud. The distribution of Class I young stellar objects (mean age ∼0.44 Myr) traces the early stage of star formation (SF) towards the cloud. At least three velocity components (around 35, 45 and 53 km s−1) are investigated towards the system. The analysis of 13CO and C18O reveals spatial and velocity connections of cloud components at around 35 and 53 km s−1. The observed positions of previously known sources, W33 Main, W33 A and O4–7I stars, are found towards a complementary distribution of these two cloud components. The filament fs1 and a previously known object W33 B are seen towards the overlapping areas of the clouds, where ongoing SF activity is evident. A scenario related to converging/colliding flows from two different velocity components appears to explain well the observed indications of SF activity in the system.
ABSTRACT We have performed a multi-wavelength analysis of a mid-infrared (MIR) bubble N37 and its surrounding environment. The selected 15′ × 15′ area around the bubble contains two molecular clouds ...(N37 cloud; 37-43 km s−1, and C25.29+0.31; 43-48 km s−1) along the line of sight. A total of seven OB stars are identified toward the bubble N37 using photometric criteria, and two of them are spectroscopically confirmed as O9V and B0V stars. The spectro-photometric distances of these two sources confirm their physical association with the bubble. The O9V star appears to be the primary ionizing source of the region, which is also in agreement with the desired Lyman continuum flux analysis estimated from the 20 cm data. The presence of the expanding H ii region is revealed in the N37 cloud, which could be responsible for the MIR bubble. Using the 13CO line data and photometric data, several cold molecular condensations as well as clusters of young stellar objects (YSOs) are identified in the N37 cloud, revealing ongoing star formation (SF) activities. However, the analysis of ages of YSOs and the dynamical age of the H ii region do not support the origin of SF due to the influence of OB stars. The position-velocity analysis of 13CO data reveals that two molecular clouds are interconnected by a bridge-like structure, favoring the onset of a cloud-cloud collision process. The SF activities (i.e., the formation of YSO clusters and OB stars) in the N37 cloud are possibly influenced by the cloud-cloud collision.
In the direction of l = 17 6-19°, the star-forming sites Sh 2-53 and IRAS 18223-1243 are prominently observed, and seem to be physically detached from each other. Sh 2-53 has been investigated at the ...junction of the molecular filaments, while a larger-scale environment of IRAS 18223-1243 remains unexplored. The goal of this paper is to investigate the star formation processes in the IRAS site (area ∼0 4 × 0 4). Based on the GRS 13CO line data, two molecular clouds, peaking at velocities of 45 and 51 km s−1, are found. In the position-velocity plots, a relatively weak 13CO emission is detected at intermediate velocities (i.e., 47.5-49.5 km s−1) between these two clouds, illustrating a link between two parallel elongated velocity structures. These clouds are physically connected in both space and velocity. The MAGPIS data at 20 cm trace free-free continuum emission toward the IRAS 18223-1243 source. Using the Spitzer and UKIDSS photometric data, we have identified infrared-excess young stellar objects (YSOs), and have observed their groups toward the intersection zones of the clouds. IRAS 18223-1243 is also spatially seen at an interface of the clouds. Considering these observational findings, we propose the onset of the collision of two clouds in the IRAS site about 1 Myr ago, which triggered the birth of massive star(s) and the YSO groups. A nonuniform distribution of the GPIPS H-band starlight mean polarization angles is also observed toward the colliding interfaces, indicating the impact of the collision on the magnetic field morphology.
Abstract
The paper presents an analysis of multiwavelength data of a nearby star-forming site, the IC 5146 dark streamer (
d
∼ 600 pc), which has been treated as a single and long filament,
fl
. Two ...hub-filament systems (HFSs) are known to exist toward the eastern and the western ends of
fl
. Earlier published results favor simultaneous evidence of HFSs and end-dominated collapse (EDC) in
fl
. A Herschel column density map (resolution ∼13.″5) reveals two intertwined sub-filaments (i.e.,
fl-A
and
fl-B
) toward
fl
, displaying a nearly double helix-like structure. This picture is also supported by the C
18
O(3–2) emission. The
fray and fragment
scenario may explain the origin of intertwined sub-filaments. In the direction of
fl
, two cloud components around 2 and 4 km s
−1
are depicted using
13
CO(1–0) and C
18
O(1–0) emission and are connected in velocity space. The HFSs are spatially found at the overlapping areas of these cloud components and can be explained by the cloud–cloud collision scenario. Nonthermal gas motion in
fl
with a larger Mach number is found. The magnetic field position angle measured from the filament’s long axis shows a linear trend along the filament. This signature is confirmed in the other nearby EDC filaments, presenting a more quantitative confirmation of the EDC scenario. Based on our observational outcomes, we witness multiple processes operational in the IC 5146 streamer. Overall, the streamer can be recognized as the first reliable candidate for edge collapse, HFSs, and intertwined sub-filaments.
ABSTRACT
With the aim of understanding the role of outflows in star formation, we performed a statistical study of the physical parameters of outflows in 11 massive protoclusters associated with ...ultracompact H ii regions. A total of 106 outflow lobes are identified in these protoclusters using the ALMA CO (3–2), HCN (4–3), and HCO+ (4–3) line observations. Although the position angles of outflow lobes do not differ in these three tracers, HCN and HCO+ tend to detect lower terminal velocity of the identified outflows compared to CO. The majority of the outflows in our targets are young with typical dynamical time-scales of 102–104 yr, and are mostly composed of low-mass outflows along with at least one high-mass outflow in each target. An anticorrelation of outflow rate with dynamical time-scale indicates that the outflow rate possibly decreases with time. Also, a rising trend of dynamical time-scale with the mass of the associated core hints that the massive cores might have longer accretion histories than the low-mass cores. Estimation of different energies in these protoclusters shows that outflows studied here cannot account for the generation of the observed turbulence, but can sustain the turbulence at the current epoch as the energy injection rate from the outflows is similar to the estimated dissipation rate.
We present a multiwavelength analysis of a ∼30′ × 30′ area around the Sh 2-53 region (hereafter S53 complex), which is associated with at least three H ii regions, two mid-infrared bubbles (N21 and ...N22), and infrared dark clouds. The 13CO line data trace the molecular content of the S53 complex in a velocity range of 36-60 km s−1 and show the presence of at least three molecular components within the selected area along this direction. Using the observed radio continuum flux of the H ii regions, the derived spectral types of the ionizing sources agree well with the previously reported results. The S53 complex harbors clusters of young stellar objects (YSOs) that are identified using the photometric 2-24 m magnitudes. It also hosts several massive condensations ( ) that are traced in the Herschel column density map. The complex is found at the junction of at least five molecular filaments, and the flow of gas toward the junction is evident in the velocity space of the 13CO data. Together, the S53 complex is embedded in a very similar "hub-filament" system to those reported in Myers, and the active star formation is evident toward the central "hub" inferred by the presence of the clustering of YSOs.
To probe the ongoing physical mechanism, we studied a wide-scale environment around AFGL 5142 (area ∼25 pc × 20 pc) using a multiwavelength approach. The Herschel column density (N(H2)) map reveals a ...massive inverted Y-like structure (mass ∼6280 M ), 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(H2) > 4.5 × 1021 cm−2. The 12CO and 13CO line data also show two elongated cloud components (around −1.5 and −4.5 km s−1) toward the inverted Y-like structure, which are connected in the velocity space. First moment maps of CO confirm the presence of two intertwined filamentary clouds along the line of sight. These results explain the morphology of the inverted Y-like structure through a combination of two different filamentary clouds, which are also supported by the distribution of the cold H i gas. Based on the distribution of young stellar objects (YSOs), star formation (SF) activities are investigated toward the inverted Y-like structure. The northern end of the structure hosts AFGL 5142 and tracers of massive SF, where high surface density of YSOs (i.e., 5-240 YSOs pc−2) reveals strong SF activity. Furthermore, noticeable YSOs are found toward the overlapping zones of the clouds. All this observational evidence supports a scenario of collision/interaction of two elongated filamentary clouds/flows, which appears to explain SF history in the site AFGL 5142.
Abstract
We report the observational findings of the Sh2-112 H
ii
region by using the multiwavelength data analysis ranging from optical to radio wavelengths. This region is powered by the massive ...O8V-type star BD +45 3216. The surface density distribution and minimum spanning tree analyses of the young stellar object (YSO) candidates in the region reveal their groupings toward the western periphery of the H
ii
region. A GMRT radio continuum emission peak is found toward the northwest boundary of the H
ii
region and is investigated as a compact/ultracompact H
ii
region candidate powered by a B0–B0.5-type star. Toward the southwest direction, a prominent curved rim-like structure is found in the H
α
image and GMRT radio continuum maps, where the H
2
and
13
CO emission is also observed. These results suggest the existence of the ionized boundary layer (IBL) on the surface of the molecular cloud. This IBL is found to be overpressured with respect to the internal pressure of the surrounding molecular cloud. This implies that the shocks are propagating/propagated into the molecular cloud, and the young stars identified within it are likely triggered due to the massive star. It is also found that this region is ionization-bounded toward the west and density-bounded toward the east. Based on the distribution of the ionized gas, molecular material, and YSO candidates, we propose that the Sh2-112 H
ii
region is a good candidate for the blister-type H
ii
region that has been evolved on the surface of a cylindrical molecular cloud.
ABSTRACT
The paper presents an analysis of multiwavelength data of two Lynds Bright Nebulae (LBNs), LBN 140.07+01.64 and LBN 140.77−1.42. The 1420-MHz continuum map reveals an extended Y-shaped ...feature (linear extent ∼3.7°), which consists of a linear part and a V-like structure. The sites LBN 140.07+01.64 and AFGL 437 are located towards the opposite sides of the V-like structure, and LBN 140.77−1.42 is spatially seen towards the linear part. Infrared-excess sources are traced towards the entire Y-feature, suggesting star formation activities. Infrared and submillimetre images show the presence of at least two large-scale dust filaments extended towards the LBN sources. The Herschel maps, which are available only towards the northern and central parts of the Y-feature, display the presence of higher column density (≥2.4 × 1021 cm−2) of materials towards the filaments. Using the 12CO(1–0) line data, the distribution of molecular gas at −42.7, −34.4 km s−1 traces the cloud associated with the Y-feature, and confirms the existence of filaments. The large-scale filaments appear to be possibly spatially twisted. There is a hint of an oscillatory-like velocity pattern along both the filaments, favouring their proposed twisted nature. It is the first study showing the possible twisting of filaments, which is more prominent in the northern and central parts of the Y-feature. This possible twisting/coupling of the large-scale filaments appears to be responsible for the observed star formation (including known OB stars). The proposed physical process and the energetics of OB stars together seem to explain the origin of the ionized Y-feature.
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