arXiv subjects

L. K. Dewangan

Publications and source records attributed to L. K. Dewangan.

At least 55 records · Page 3Linked to original sources

arXiv2021

ALMA discovery of a dual dense probably rotating outflow from a massive young stellar object G18.88MME

We report the discovery of a very dense jet-like fast molecular outflow surrounded by a wide-angle wind in a massive young stellar object (MYSO) G18.88MME (stellar mass $\sim$8 M$_{\odot}$) powering an Extended Green Object G18.89$-$0.47. Four cores MM1-4 are identified in the Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum map (resolution $\sim$0.$"$8) toward G18.88MME, and are seen at the center of the emission structure (extent $\sim$0.3 pc $\times$ 0.2 pc) detected in the ALMA map. G18.88MME is embedded in the core MM1 (mass $\sim$13-18 M$_{\odot}$), where no radio continuum emission is detected. The molecular outflow centered at MM1 is investigated in the SiO(5-4), HC$_{3}$N(24-23) and $^{13}$CO(2-1) lines. The detection of HC$_{3}$N in the outflow is rare in MYSOs and indicates its very high density. The position-velocity diagrams display a fast narrow outflow (extent $\sim$28000 AU) and a slower wide-angle more extended outflow toward MM1, and both of these components show a transverse velocity gradient indicative of a possible rotation. All these observed features together make G18.88MME as a unique object for studying the unification of the jet-driven and wind-driven scenarios of molecular outflows in MYSOs.

astro-ph.GA↗

arXiv2021

Unraveling the inner substructure of new candidate hub-filament system in the HII region G25.4NW

We present multi-scale and multi-wavelength data of the Galactic HII region G25.4-0.14 (hereafter G25.4NW, distance ~5.7 kpc). The SHARC-II 350 micron continuum map displays a hub-filament configuration containing five parsec scale filaments and a central compact hub. Through the 5 GHz radio continuum map, four ionized clumps (i.e., Ia-Id) are identified toward the central hub, and are powered by massive OB-stars. The Herschel temperature map depicts the warm dust emission (i.e., Td ~23-39 K) toward the hub. High resolution Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum map (resolution ~0".82 X 0".58) reveals three cores (c1-c3; mass ~80-130 Msun) toward the ionized clumps Ia, and another one (c4; mass ~70 Msun) toward the ionized clump Ib. A compact near-infrared (NIR) emission feature (extent ~0.2 pc) is investigated toward the ionized clump Ia excited by an O8V-type star, and contains at least three embedded K-band stars. In the direction of the ionized clump Ia, the ALMA map also shows an elongated feature (extent ~0.2 pc) hosting the cores c1-c3. All these findings together illustrate the existence of a small cluster of massive stars in the central hub. Considering the detection of the hub-filament morphology and the spatial locations of the mm cores, a global non-isotropic collapse (GNIC) scenario appears to be applicable in G25.4NW, which includes the basic ingredients of the global hierarchical collapse and clump-fed accretion models. Overall, the GNIC scenario explains the birth of massive stars in G25.4NW.

astro-ph.GA↗

arXiv2021

Magnetic fields and Star Formation around HII regions: The S235 complex

Magnetic fields are ubiquitous and essential in star formation. In particular, their role in regulating formation of stars across diverse environments like HII regions needs to be well understood. In this study, we present magnetic field properties towards the S235 complex using near-infrared (NIR) $H$-band polarimetric observations, obtained with the Mimir and POLICAN instruments. We selected 375 background stars in the field through combination of Gaia distances and extinctions from NIR colors. The plane-of-sky (POS) magnetic field orientations inferred from starlight polarization angles reveal a curved morphology tracing the spherical shell of the HII region. The large-scale magnetic field traced by Planck is parallel to the Galactic plane. We identified 11 dense clumps using $1.1\,\mathrm{mm}$ dust emission, with masses between $33-525\,\rm M_\odot$. The clump averaged POS magnetic field strengths were estimated to be between $36-121\,\mathrm{μG}$, with a mean of ${\sim}65\,\mathrm{μG}$. The mass-to-flux ratios for the clumps are found to be sub-critical with turbulent Alfvén Mach numbers less than 1, indicating a strongly magnetized region. The clumps show scaling of magnetic field strength vs density with a power-law index of $0.52\pm0.07$, similar to ambipolar diffusion models. Our results indicate the S235 complex is a region where stellar feedback triggers new stars and the magnetic fields regulate the rate of new star formation.

astro-ph.GA↗

arXiv2020

Star formation and evolution of blister-type H{\sc ii} region Sh2-112

We report the observational findings of the Sh2-112 H{\sc ii} region by using the multiwavelength data analysis ranging from optical to radio wavelengths. This region is powered by a 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{\sc ii} region. A GMRT radio continuum emission peak is found toward the north-west boundary of the H{\sc ii} region and is investigated as a compact/ultra-compact H{\sc ii} region candidate powered by a B0-B0.5 type star. Toward the south-west 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 over-pressurized 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-direction and density bounded toward the east-direction. Based on the distribution of the ionized gas, molecular material, and the YSO candidates; we propose that the Sh2-112 H{\sc ii} region is a good candidate for the blister-type H{\sc ii} region which has been evolved on the surface of a cylindrical molecular cloud.

astro-ph.SR↗

arXiv2020

New insights in the HII region G18.88-0.49: hub-filament system and accreting filaments

We present an analysis of multi-wavelength observations of an area of 0.27 deg x 0.27 deg around the Galactic HII region G18.88-0.49, which is powered by an O-type star (age ~10^5 years). The Herschel column density map reveals a shell-like feature of extension ~12 pc x 7 pc and mass ~2.9 x 10^4 Msun around the HII region; its existence is further confirmed by the distribution of molecular (12CO, 13CO, C18O, and NH3) gas at [60, 70] km/s. Four subregions are studied toward this shell-like feature, and show a mass range of ~0.8-10.5 x 10^3 Msun. These subregions associated with dense gas are dominated by non-thermal pressure and supersonic non-thermal motions. The shell-like feature is associated with the HII region, Class I protostars, and a massive protostar candidate, illustrating the ongoing early phases of star formation (including massive stars). The massive protostar is found toward the position of the 6.7 GHz methanol maser, and is associated with outflow activity. Five parsec-scale filaments are identified in the column density and molecular maps, and appear to be radially directed to the dense parts of the shell-like feature. This configuration is referred to as a "hub-filament" system. Significant velocity gradients (0.8-1.8 km/s/pc) are observed along each filament, suggesting that the molecular gas flows towards the central hub along the filaments. Overall, our observational findings favor a global non-isotropic collapse scenario as discussed in Motte et al. (2018), which can explain the observed morphology and star formation in and around G18.88-0.49.

astro-ph.GA↗

arXiv2020

Star-forming sites IC 446 and IC 447: an outcome of end-dominated collapse of Monoceros R1 filament

We present an analysis of multi-wavelength observations of Monoceros R1 (Mon R1) complex (at d ~760 pc). An elongated filament (length ~14 pc, mass ~1465 Msun) is investigated in the complex, which is the most prominent structure in the Herschel column density map. An analysis of the FUGIN 12CO(1-0) and 13CO(1-0) line data confirms the existence of the filament traced in a velocity range of [-5, +1] km/s. The filament is found to host two previously known sites IC 446 and IC 447 at its opposite ends. A massive young stellar object (YSO) is embedded in IC 446, while IC 447 contains several massive B-type stars. The Herschel temperature map reveals the extended warm dust emission (at T_d ~ 15-21 K) toward both the ends of the filament. The Spitzer ratio map of 4.5 micron/3.6 micron emission suggests the presence of photo-dissociation regions and signature of outflow activity toward IC 446 and IC 447. Based on the photometric analysis of point-like sources, clusters of YSOs are traced mainly toward the filament ends. The filament is found to be thermally supercritical showing its tendency of fragmentation, which is further confirmed by the detection of a periodic oscillatory pattern (having a period of ~3-4 pc) in the velocity profile of 13CO. Our outcomes suggest that the fragments distributed toward the filament ends have rapidly collapsed, and had formed the known star-forming sites. Overall, the elongated filament in Mon R1 is a promising sample of the "end-dominated collapse" scenario, as discussed by Pon et al. (2011, 2012).

astro-ph.GA↗

arXiv2020

Probing the physical conditions and star formation processes in the Galactic HII region S305

We present multi-scale and multi-wavelength observations of the Galactic HII region S305, which is excited by massive O8.5V and O9.5V stars. Infrared images reveal an extended sphere-like shell (extension ~7.5 pc; at T_d = 17.5-27 K) enclosing the S305 HII region (size ~5.5 pc; age ~1.7 Myr). The extended structure observed in the Herschel temperature map indicates that the molecular environment of S305 is heated by the massive O-type stars. Regularly spaced molecular condensations and dust clumps are investigated toward the edges of the infrared shell, where the PAH and H_2 emission is also observed. The molecular line data show a signature of an expanding shell of molecular gas in S305. GMRT 610 and 1280 MHz continuum maps reveal overdensities of the ionized emission distributed around two O-type stars, which are surrounded by the horseshoe envelope (extension ~2.3 pc). A molecular gas deficient region/cavity is identified toward the center of the horseshoe envelope, which is well traced with PAH, H_2, molecular, and dust emission. The edges of the infrared shell are found to be located in the front of the horseshoe envelope. All these outcomes provide the observational evidence of the feedback of O-type stars in S305. Moreover, non-thermal radio emission is detected in S305 with an average spectral index alpha ~-0.45. The variations in alpha, ranging from -1.1 to 1.3, are explained due to soft synchrotron emission and either optically-thicker thermal emission at high frequencies or a suppression of the low-frequency emission by the Razin-Tsytovich effect.

astro-ph.GA↗

arXiv2020

Uncovering distinct environments in an extended physical system around the W33 complex

We present a multi-wavelength investigation of a large-scale physical system containing the W33 complex. The extended system (~50 pc x 37 pc) is selected based on the distribution of molecular gas at [29.6, 60.2] km/s and of 88 ATLASGAL 870 micron dust clumps at d ~2.6 kpc. The extended system/molecular cloud traced in the maps of 13CO and C18O emission contains several HII regions excited by OB stars (age ~0.3-1.0 Myr) and a thermally supercritical filament ("fs1", length ~17 pc). The filament, devoid of the ionized gas, shows dust temperature (T_d) of ~19 K, while the HII regions are depicted with T_d 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) toward the cloud. At least three velocity components (around 35, 45, and 53 km/s) are investigated toward the system. The analysis of 13CO and C18O reveals the spatial and velocity connections of cloud components around 35 and 53 km/s. The observed positions of previously known sources, W33 Main, W33 A and O4-7I stars, are found toward a complementary distribution of these two cloud components. The filament "fs1" and a previously known object W33 B are seen toward the overlapping areas of the clouds, where ongoing SF activity is evident. A scenario concerning the converging/colliding flows from two different velocity components appears to explain well the observed signposts of SF activities in the system.

astro-ph.GA↗

arXiv2020

Investigating the physical conditions in extended system hosting mid-infrared bubble N14

To observationally explore physical processes, we present a multi-wavelength study of a wide-scale environment toward l = 13.7 - 14.9 degrees containing a mid-infrared bubble N14. The analysis of 12CO, 13CO, and C18O gas at [31.6, 46] km/s reveals an extended physical system (extension ~59 pc x 29 pc), which hosts at least five groups of the ATLASGAL 870 micron dust clumps at d ~3.1 kpc. These spatially-distinct groups/sub-regions contain unstable molecular clumps, and are associated with several Class I young stellar objects (mean age ~0.44 Myr). At least three groups of ATLASGAL clumps associated with the expanding HII regions (including the bubble N14) and embedded infrared dark clouds, devoid of the ionized gas, are found in the system. The observed spectral indices derived using the GMRT and THOR radio continuum data suggest the presence of non-thermal emission with the HII regions. High resolution GMRT radio continuum map at 1280 MHz traces several ionized clumps powered by massive B-type stars toward N14, which are considerably young (age ~10^3 - 10^4 years). Locally, early stage of star formation is evident toward all the groups of clumps. The position-velocity maps of 12CO, 13CO, and C18O exhibit an oscillatory-like velocity pattern toward the selected longitude range. Considering the presence of different groups/sub-regions in the system, the oscillatory pattern in velocity is indicative of the fragmentation process. All these observed findings favour the applicability of the global collapse scenario in the extended physical system, which also seems to explain the observed hierarchy.

astro-ph.GA↗

arXiv2019

New insights in giant molecular cloud hosting S147/S153 complex: signatures of interacting clouds

In order to understand the formation of massive OB stars, we report a multi-wavelength observational study of a giant molecular cloud hosting the S147/S153 complex (size ~90 pc X 50 pc). The selected complex is located in the Perseus arm, and contains at least five HII regions (S147, S148, S149, S152, and S153) powered by massive OB stars having dynamical ages of ~0.2 - 0.6 Myr. The Canadian Galactic Plane Survey 12CO line data (beam size ~100".4) trace the complex in a velocity range of [-59, -43] km/s, and also reveal the presence of two molecular cloud components around -54 and -49 km/s in the direction of the complex. Signatures of the interaction/collision between these extended cloud components are investigated through their spatial and velocity connections. These outcomes suggest the collision of these molecular cloud components about 1.6 Myr ago. Based on the observed overlapping zones of the two clouds, the collision axis appears to be parallel to the line-of-sight. Deep near-infrared photometric analysis of point-like sources shows the distribution of infrared-excess sources in the direction of the overlapping zones of the molecular cloud components, where all the HII regions are also spatially located. All elements put together, the birth of massive OB stars and embedded infrared-excess sources seems to be triggered by two colliding molecular clouds in the selected site. High resolution observations of dense gas tracer will be required to further confirm the proposed scenario.

astro-ph.GA↗

arXiv2019

Influence of Wolf-Rayet stars on surrounding star-forming molecular clouds

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. The column densities of shells are enhanced by a minimum of 14% for one region to a maximum of 88% for another region with respect to the column densities within their central cavities. No active star formation - including molecular condensations, protostars, or ionized gas - is found inside the cavities, whereas such features are observed around the molecular shells. Although the expansion of ionized gas is considered an effective mechanism to trigger star formation, the dynamical ages of the HII regions in our sample are generally not sufficiently long to do so efficiently. Overall, our results hint at the possible importance of negative W-R wind-driven feedback on the gas-deficient cavities, where star formation is quenched as a consequence. In addition, the presence of active star formation around the molecular shells indicates that W-R stars may also assist in accumulating molecular gas, and that they could initiate star formation around those shells.

astro-ph.GA↗

arXiv2019

Cluster-forming site AFGL 5157: colliding filamentary clouds and star formation

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) shell surrounding a previously known evolved infrared cluster. Diffuse H-alpha emission is traced inside the infrared shell, suggesting the presence of massive stars in the evolved cluster. Based on the surface density analysis of young stellar objects (YSOs), embedded clusters of YSOs are traced toward the central part of FF, and are distributed around the infrared shell. Previously detected H2O masers, H2 knots, massive protostar candidates, and HII region are also seen toward the embedded clusters. Using the 12CO and 13CO line data, the central part of FF is observed at the overlapping zones of two filamentary molecular clouds (length ~12.5 pc) around -20 and -17 km/s, which are also connected in velocity. Our observational results suggest that the formation of massive stars appears to be triggered by a collision of two filamentary molecular clouds, which might have also influenced the birth of YSOs in AFGL 5157.

astro-ph.GA↗

arXiv2019

Unveiling molecular clouds toward bipolar HII region G8.14+0.23

Most recent numerical simulations suggest that bipolar HII regions, powered by O-type stars, can be formed at the interface of two colliding clouds. To observationally understand the birth of O-type stars, we present a detailed multi-wavelength analysis of an area of 1 deg x 1 deg hosting G8.14+0.23 HII region associated with an infrared bipolar nebula (BPN). Based on the radio continuum map, the HII region is excited by at least an O-type star, which is located toward the waist of the BPN. The NANTEN2 13CO line data reveal the existence of two extended clouds at [9, 14.3] and [15.3, 23.3] km/s toward the site G8.14+0.23, which are connected in the position-velocity space through a broad-bridge feature at the intermediate velocity range. A "cavity/intensity-depression" feature is evident in the blueshifted cloud, and is spatially matched by the "elongated redshifted cloud". The spatial and velocity connections of the clouds suggest their interaction in the site G8.14+0.23. The analysis of deep near-infrared photometric data reveals the presence of clusters of infrared-excess sources, illustrating ongoing star formation activities in both the clouds. The O-type star is part of the embedded cluster seen in the waist of the BPN, which is observed toward the spatial matching zone of the cavity and the redshifted cloud. The observational results appear to be in reasonable agreement with the numerical simulations of cloud-cloud collision (CCC), suggesting that the CCC process seems to be responsible for the birth of the O-type star in G8.14+0.23.

astro-ph.GA↗

arXiv2018

The study of a system of H II regions toward l = 24.8 deg, b = 0.1 deg at the Galactic bar - Norma arm interface

To probe the star formation (SF) process, we present a thorough multi-wavelength investigation of several H II regions located toward l = 24.8 deg, b = 0.1 deg. A system of at least five H II regions including the mid-infrared bubble N36 (hereafter "system N36"; extension ~35 pc) is observationally investigated, and is located at a distance of 6.0 kpc. With this distance, the system N36 is found to be situated at the interface of the Galactic bar and the Norma Galactic arm in our Galaxy, where one may expect the collisions of molecular clouds due to the bar potential. Each H II region (dynamical age ~0.4 - 1.3 Myr) in the system is powered by an O-type star. The system contains 27 ATLASGAL dust clumps at 870 micron. Several clumps are massive (> 10^3 M_sun), and have high bolometric luminosity (> 10^3 L_sun). Using the GRS 13CO line data, in the direction of the system N36, two velocity components are found around 109 and 113 km/s, and are linked in the velocity space. The morphological analysis of 13CO favours the presence of interacting molecular clouds in the system. Four H II regions and two 6.7 GHz masers are spatially observed at the common areas of the two clouds. The analysis of the Spitzer photometric data also traces the noticeable SF activity in the system. Considering the observational outcomes, the formation of O-type stars (including ongoing SF) in the system appears to be triggered by the collisions of molecular clouds at the bar-arm interface.

astro-ph.GA↗

arXiv2018

Filamentary Structures and Star Formation Activities in the Sites S234, V582, and IRAS 05231+3512

To investigate the physical processes, we present observational results of the sites S234, V582, and IRAS 05231+3512 situated toward l = 171.7 - 174.1 degrees. Based on the CO line data, we find that these sites are not physically connected, and contain at least one filament (with length > 7 pc). The observed line masses (M_line,obs) of the filaments associated with V582 and IRAS 05231+3512 are ~37 and ~28 M_sun/pc, respectively. These filaments are characterized as thermally supercritical, and harbor several clumps. Groups of infrared-excess sources and massive B-type stars are observed toward the filament containing V582, while a very little star formation (SF) activity is found around IRAS 05231+3512. Our results favour radial collapse scenario in the filaments harboring V582 and IRAS 05231+3512. In the site S234, two filaments (i.e. ns1 (M_line,obs ~130 M_sun/pc) and ns2 (M_line,obs ~45 M_sun/pc)) are identified as thermally supercritical. An extended temperature structure at 27-30 K surrounds a relatively cold (~19 K) ~8.9 pc long filament ns1. At least four condensations (M_clump ~70-300 M_sun) are seen in ns1, and are devoid of the GMRT 610 MHz radio emission. The filament ns2 hosting clumps is devoid of ongoing SF, and could be at an early stage of fragmentation. An intense SF activity, having the SF efficiency ~3.3% and SF rate ~40-20 M_sun/Myr (for t_sf ~1-2 Myr), is observed in ns1. The feedback of massive stars in S234 seems to explain the observed SF in the filament ns1.

astro-ph.GA↗

arXiv2018

Cloud-Cloud Collision Induced Star Formation in IRAS 18223-1243

In the direction of l = 17.6 - 19 deg, 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 deg x 0.4 deg). Based on the GRS 13CO line data, two molecular clouds, peaking at velocities of 45 and 51 km/s, 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) 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 non-uniform 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.

astro-ph.GA↗

arXiv2018

The embedded ring-like feature and star formation activities in G35.673-00.847

We present a multi-wavelength study to probe the star formation (SF) process in the molecular cloud linked with the G35.673-00.847 site (hereafter MCG35.6), which is traced in a velocity range of 53-62 km/s. Multi-wavelength images reveal a semi-ring-like feature (associated with ionized gas emission) and an embedded face-on ring-like feature (without the NVSS 1.4 GHz radio emission; where 1-sigma ~ 0.45 mJy/beam) in the MCG35.6. The semi-ring-like feature is originated by the ionizing feedback from a star with spectral type B0.5V-B0V. The central region of the ring-like feature does not contain detectable ionized gas emission, indicating that the ring-like feature is unlikely to be produced by the ionizing feedback from a massive star. Several embedded Herschel clumps and young stellar objects (YSOs) are identified in the MCG35.6, tracing the ongoing SF activities within the cloud. The polarization information from the Planck and GPIPS data trace the plane-of-sky magnetic field, which is oriented parallel to the major axis of the ring-like feature. At least five clumps (having M_clump ~ 740 - 1420 M_sun) seem to be distributed in an almost regularly spaced manner along the ring-like feature and contain noticeable YSOs. Based on the analysis of the polarization and molecular line data, three subregions containing the clumps are found to be magnetically supercritical in the ring-like feature. Altogether, the existence of the ring-like feature and the SF activities on its edges can be explained by the magnetic field mediated process as simulated by Li & Nakamura (2002).

astro-ph.GA↗

arXiv2017

Star formation in the Sh 2-53 region influenced by accreting molecular filaments

We present a multi-wavelength analysis of a $\sim$30$' \times$30$'$ 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 $^{13}$CO 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 $μ$m magnitudes. It also hosts several massive condensations (3000-30000 $M_\odot$) which are traced in the {\em 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 $^{13}$CO 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 towards the central "hub" inferred by the presence of the clustering of YSOs.

astro-ph.GA↗