We present an analysis of late-O/early-B-powered, parsec-sized bubbles and associated star-formation using 2MASS, GLIMPSE, MIPSGAL and MAGPIS surveys. Three bubbles were selected from the Churchwell et al. (2007) catalog. We confirm that the structure identified in Watson et al. (2008) holds in less energetic bubbles, i.e. a PDR, identified by 8 um emission due to PAHs surrounds hot dust, identified by 24 um emission and ionized gas, identified by 20 cm continuum. We estimate the dynamical age of two bubbles by comparing bubble sizes to numerical models of Hosokawa & Inutsuka (2006). We also identify and analyze candidate young stellar objects (YSOs) using SED fitting and identify sites of possible triggered star-formation. Lastly, we identify likely ionizing sources for two sources based on SED fitting.
The interstellar medium and the massive stellar content toward the SNR G18.1-0.1 and neighboring HII regions
我们对SNR G18.1-0.1和附近的几个HII区域（红外尘埃泡N21和N22，以及HII区域G018.149-00.283和G18.197-00.181）进行了多波长研究。我们的目标是提供观测证据支持大质量恒星通常诞生于同一分子云的星系团中，然后沿着它们的演化产生不同的邻近物体，例如HII区域、星际气泡和超新星遗迹。我们认为，在这项工作中分析的对象属于同一个复杂的距离约4千秒差距。利用分子数据，我们检查了朝向这个复合体的星际介质，并从光学和X射线观测中寻找该区域的OB型恒星。分析公开的13 CO J=1- 0数据，我们发现几种分子结构非常可能与HII区/SNR复合物有关。我们认为，分子气体很可能被席卷和形状的HII区域的扩张。利用位于阿根廷CASLEO的2.15米望远镜的分光光学观测，我们发现了三颗O型星，它们很可能分别激发了N21和N22泡，以及N22泡以北的一个未编目的HII区。此外，我们还发现了4颗B 0 -5恒星，其中一颗朝向气泡N22，另一颗位于HII区域G18.149-0.283。通过检查钱德拉源表，我们发现了两个点X射线源，我们认为其中一个是早期的O型星。最后考察了该区域周围的大尺度星际介质。我们发现了一个大约70 pc x 28 pc的大分子壳，其中分析的复合物似乎位于其南部边界。
We carried out a molecular line study toward the three Spitzer bubbles S116, S117 and S118 which show active formation of high-mass stars. We found molecular gas consisting of two components with velocity difference of {$\sim 5$ \kms}. One of them, the small cloud, has typical velocity of {$-63$ \kms} \ and the other, the large cloud, has that of $-58$ \kms. The large cloud has a nearly circular intensity depression whose size is similar to the small cloud. We present an interpretation that the cavity was created by a collision between the two clouds and the collision compressed the gas into a…
We report the discovery of a double-peaked Lyman-alpha profile in a galaxy at $z=6.803$, A370p\_z1, in the parallel Frontier Field of Abell 370. The velocity separation between the blue and red peaks of the Lyman-$α$ profile ($Δv=101_{-19}^{+38} (\pm48)\,\text{km s}^{-1}$) suggests an extremely high escape fraction of ionising photons $> 59(51)\% (2σ)$. The spectral energy distribution indicates a young ($50$ Myr), star-forming ($12\pm 6 \, \rm{M}_\odot \rm{yr}^{-1}$) galaxy with an IRAC excess implying strong [OIII]+H$β$ emission. On the basis of the high escape fraction measured, we demonstr…
Winds from young massive stars contribute a large amount of energy to their host molecular clouds. This has consequences for the dynamics and observable structure of star-forming clouds. In this paper, we present radiative magnetohydrodynamic simulations of turbulent molecular clouds that form individual stars of 30, 60 and 120 solar masses emitting winds and ultraviolet radiation following realistic stellar evolution tracks. We find that winds contribute to the total radial momentum carried by the expanding nebula around the star at 10 % of the level of photoionisation feedback, and have only…
We utilized the Very Large Array to make multifrequency polarization measurements of 20 radio sources viewed through the IC 1805 HII region and "Superbubble", as well as in the immediate vicinity. The measurements at frequencies between 4.33 and 7.76 GHz yield Faraday rotation measures along 27 lines of sight to these sources (some sources have more than one component). The Faraday rotation measures (RM) are used to probe the plasma structure of the IC 1805 HII region and to test the degree to which the Galactic magnetic field is heavily modified (amplified) by the dynamics of the HII region. …
Thousands of ring-like bubbles appear on infrared images of the Galaxy plane. Most of these infrared bubbles form during expansion of HII regions around massive stars. However, the physical effects that determine their morphology are still under debate. Namely, the absence of the infrared emission toward the centres of the bubbles can be explained by pushing the dust grains by stellar radiation pressure. At the same time, small graphite grains and PAHs are not strongly affected by the radiation pressure and must be removed by another process. Stellar ultraviolet emission can destroy the smalle…
Revealing the 3D dynamics of HII regions and their associated molecular clouds is important for understanding the longstanding problem as to how stellar feedback affects the density structure and kinematics of the interstellar medium. We employed observations of the HII region RCW 120 in [CII], observed within the SOFIA legacy program FEEDBACK, and the $^{12}$CO and $^{13}$CO (3$\to$2) lines, obtained with APEX. In addition we used HI data from the Southern Galactic Plane Survey. Two radiative transfer models were used to fit the observed data. A line profile analysis with the 1D non-LTE radia…
Young HII regions are an important site to study O star formation based on distributions of ionized and molecular gas. We revealed that two molecular clouds at $\sim 48$ km s$^{-1}$ and $\sim 53$ km s$^{-1}$ are associated with the HII regions G018.149-00.283 in RCW 166 by using the JCMT CO High-Resolution Survey (COHRS) of the $^{12}$CO ($J$=3--2) emission. G018.149-00.283 comprises a bright ring at 8 $μ$m and an extended HII region inside the ring. The $\sim 48$ km s$^{-1}$ cloud delineates the ring, and the $\sim 53$ km s$^{-1}$ cloud is located within the ring, indicating a complementary d…
We present cosmological ($30-400$ Mpc) distributions of neutral hydrogen (HI) in the inter-galactic medium (IGM) traced by Ly$α$ Emitters (LAEs) and QSOs at $z=2.1-2.5$, selected with the data of the on-going Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) and the eBOSS survey. We investigate spatial correlations of LAEs and QSOs with HI tomography maps reconstructed from HI Ly$α$ forest absorption in the spectra of background galaxies and QSOs obtained by the CLAMATO survey and this study, respectively. In the cosmological volume far from QSOs, we find that LAEs reside in regions of st…
The Fermi Bubbles are two giant gamma-ray emitting lobes extending 55$^{\circ}$ above and below the Galactic Center. While the Northern Bubble has been extensively studied in ultraviolet (UV) absorption, little is known about the gas kinematics of the southern Bubble. We use UV absorption-line spectra from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope to probe the southern Fermi Bubble using a sample of 17 background AGN projected behind or near the Bubble. We measure the incidence of high-velocity clouds (HVC), finding that four out of six sightlines passing through the …
We present a comprehensive statistical analysis of star-forming objects located in the vicinities of 1 360 bubble structures throughout the Galactic Plane and their local environments. The compilation of ~70 000 star-forming sources, found in the proximity of the ionized (Hii) regions and detected in both Hi-GAL and GLIMPSE surveys, provided a broad overview of the different evolutionary stages of star-formation in bubbles, from prestellar objects to more evolved young stellar objects (YSOs). Surface density maps of star-forming objects clearly reveal an evolutionary trend where more evolved s…
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 o…
Aiming at studying the physical properties of Galactic IR bubbles and to explore their impact in triggering massive star formation, we perform a multiwavelength analysis of the bubble HII region Sh2-39 (N5) and its environs. To analyze the molecular gas we use CO(3-2) and HCO+(4-3) line data obtained with the ASTE telescope. To study the physical characteristics of the dust, we make use of archival data from ATLASGAL, Herschel, and MSX, while the ionized gas was studied making use of NVSS data. We use public IR point source catalogs to search for candidate YSOs in the region. To investigate th…
The hot halo gas distribution in the inner Milky Way (MW) contains key fossil records of the past energetic feedback processes in the Galactic center. Here we adopt a variety of spherical and disk-like MW halo gas models as initial conditions in a series of simulations to investigate the formation of the Fermi bubbles in the jet-shock scenario. The simulation results are compared directly with relevant X-ray and gamma-ray observations of the Fermi bubbles to constrain the halo gas distribution in the inner Galaxy before the Fermi bubble event. Our best-fit gas density distribution can be descr…
Using the CoDa II simulation, we study the Ly$α$ transmissivity of the intergalactic medium (IGM) during reionization. At $z>6$, a typical galaxy without an active galactic nucleus fails to form a proximity zone around itself due to the overdensity of the surrounding IGM. The gravitational infall motion in the IGM makes the resonance absorption extend to the red side of Ly$α$, suppressing the transmission up to roughly the circular velocity of the galaxy. In some sight lines, an optically thin blob generated by a supernova in a neighboring galaxy results in a peak feature, which can be mistake…
We report an observational study of the Galactic HII region Sh 2-305/S305 using the [CII] 158 $μ$m line data, which are used to examine the gas dynamics and structure of photodissociation regions. The integrated [CII] emission map at [39.4, 49.5] km s$^{-1}$ spatially traces two shell-like structures (i.e., inner and outer neutral shells) having a total mass of $\sim$565 M$_\odot$. The inner neutral shell encompasses an O9.5V star at its centre and has a compact ring-like appearance. However, the outer shell is seen with more extended and diffuse [CII] emission, hosting an O8.5V star at its ce…
Direct detection of regions of ionized hydrogen (HII) has been suggested as a promising probe of cosmic reionization. Observing the redshifted 21-cm signal of hydrogen from the epoch of reionization (EoR) is a key scientific driver behind new-generation, low-frequency radio interferometers. We investigate the feasibility of combining low-frequency observations with the Square Kilometre Array and near infra-red survey data of the Wide-Field Infrared Survey Telescope to detect cosmic reionization by imaging HII bubbles surrounding massive galaxies during the cosmic dawn. While individual bubbles…
Understanding Ly$α$ emitting galaxies (LAEs) can be a key to reveal cosmic reionization and galaxy formation in the early Universe. Based on halo merger trees and Ly$α$ radiation transfer calculations, we model redshift evolution of LAEs and their observational properties at $z \ge 6$. We consider ionized bubbles associated with individual LAEs and IGM transmission of Ly$α$ photons. We find that Ly$α$ luminosity tightly correlates with halo mass and stellar mass, while the relation with star formation rate has a large dispersion. Comparing our models with the observed luminosity function by Ko…
In this paper we make predictions for the behaviour of wind bubbles around young massive stars using analytic theory. We do this in order to determine why there is a discrepancy between theoretical models that predict that winds should play a secondary role to photoionisation in the dynamics of HII regions, and observations of young HII regions that seem to suggest a driving role for winds. In particular, regions such as M42 in Orion have neutral hydrogen shells, suggesting that the ionising radiation is trapped closer to the star. We first derive formulae for wind bubble evolution in non-unif…
The environment of S187, a nearby H II region (1.4$\pm$0.3 kpc), is analyzed. A surrounding shell has been studied in the H I line, molecular lines, and also in infrared and radio continua. We report the first evidence of a clumpy HI environment in its photodissociation region. A background radio galaxy enables the estimation of the properties of cold atomic gas. The estimated atomic mass fraction of the shell is $\sim$260~M$_{\odot}$, the median spin temperature is $\sim$50~K, the shell size is $\sim$4 pc with typical wall width around 0.2 pc. The atomic shell consists of $\sim$100 fragments.…
Context: How do expanding HII regions interact with their environmental cloud? This is one of the central questions driving the SOFIA legacy program FEEDBACK. Here, we present a case study toward the prototypical H{\sc ii} region NGC7538. Methods: With SOFIA we mapped an area of ~210'^2 around NGC7538 in the [CII] line at 1.9THz. Complementary observed atomic carbon [CI] and high-J CO(8-7) data as well as archival NIR/FIR, cm continuum, CO(3-2) and HI data are folded into the analysis. Results: While the overall [CII] morphology follows the general ionized gas, the channel maps show multiple b…
We used the $Hα$ images from a large sample of nearby late-type dwarf galaxies to investigate properties of their emission structure. The sample consists of three hundred galaxies of the irregular (Irr), Magellanic irregular (Im), blue compact dwarf (BCD), and transition (Tr) types situated within a distance of 11 Mpc. In each galaxy, we indicated: the number of compact HII-regions, the presence of bubble-like or filament-like structures, the presence of a faint diffuse emission, and a sign of the global burst. The larger luminosity of a galaxy, the greater number of compact HII-sources in it.…
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 assoc…
IC342 is a nearby, late-type spiral galaxy with a young nuclear star cluster surrounded by several giant molecular clouds. The IC342 nuclear region is similar to the Milky Way and therefore provides an interesting comparison. We explore star formation in the nucleus using radio recombination line (RRL) and continuum emission at 5, 6.7, 33, and 35 GHz with the JVLA. These radio tracers are largely unaffected by dust and therefore sensitive to all of the thermal emission from the ionized gas produced by early-type stars. We resolve two components in the RRL and continuum emission within the nucl…
Fine structure of the density distribution in giant molecular clouds (GMC) around W43 (G31+00+90 km/s at $\sim 5.5$ kpc) was analyzed using the FUGIN$^*$ CO-line survey at high-angular ($20''\sim 0.5$ pc) and velocity (1.3 km/s) resolutions ($^*$Four-receiver-system Unbiased Galactic Imaging survey with the Nobeyama 45-m telescope). The GMCs show highly turbulent structures, and the eddies are found to exhibit spherical bubble morphology appearing in narrow ranges of velocity channels. The bubbles are dark in radio continuum emission, unlike usual supernova remnants (SNR) or HII regions, and i…
Large infrared and millimeter wavelength surveys of the Galactic plane have unveiled more than 600 new bubble HII regions and more than 3000 candidate star clusters. We present a study of the candidate clusters MCM2005b72, DBS2003-157, DBS2003-172, and MCM2005b77, based on near-infrared spectroscopy taken with SofI on the NTT and infrared photometry from the 2MASS, VVV, and GLIMPSE surveys. We find that (1) MCM2005b72 and DBS2003-157 are subregions of the same star-forming region, HII GRS G331.34-00.36 (bubble S62). MCM2005b72 coincides with the central part of this HII region, while DBS2003-1…
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…
We study the HII regions associated with the NGC 6334 molecular cloud observed in the sub-millimeter and taken as part of the B-fields In STar-forming Region Observations (BISTRO) Survey. In particular, we investigate the polarization patterns and magnetic field morphologies associated with these HII regions. Through polarization pattern and pressure calculation analyses, several of these bubbles indicate that the gas and magnetic field lines have been pushed away from the bubble, toward an almost tangential (to the bubble) magnetic field morphology. In the densest part of NGC 6334, where the …
