scholarly journals In Search of Infall Motion in Molecular Clumps. III. HCO+ (1-0) and H13CO+ (1-0) Mapping Observations toward Confirmed Infall Sources

2021 ◽  
Vol 922 (2) ◽  
pp. 144
Author(s):  
Yang Yang ◽  
Zhibo Jiang ◽  
Zhiwei Chen ◽  
Yiping Ao ◽  
Shuling Yu
Keyword(s):  
Star Formation ◽  
Column Density ◽  
Massive Star ◽  
Radiation Transfer ◽  
Line Profiles ◽  
Signal To Noise ◽  
Star Forming ◽  
Integrated Intensity ◽  
The Mean ◽  
Blue Line

Abstract The study of infall motion helps us to understand the initial stages of star formation. In this paper, we use the IRAM 30 m telescope to make mapping observations of 24 infall sources confirmed in previous work. The lines we use to track gas infall motions are HCO+ (1-0) and H13CO+ (1-0). All 24 sources show HCO+ emissions, while 18 sources show H13CO+ emissions. The HCO+ integrated intensity maps of 17 sources show clear clumpy structures; for the H13CO+ line, 15 sources show clumpy structures. We estimated the column density of HCO+ and H13CO+ using the RADEX radiation transfer code, and the obtained [HCO+]/[H2] and [H13CO+]/[HCO+] of these sources are about 10−11–10−7 and 10−3–1, respectively. Based on the asymmetry of the line profile of the HCO+, we distinguish these sources: 19 sources show blue asymmetric profiles, and the other sources show red profiles or symmetric peak profiles. For eight sources that have double-peaked blue line profiles and signal-to-noise ratios greater than 10, the RATRAN model is used to fit their HCO+ (1-0) lines, and to estimate their infall parameters. The mean V in of these sources is 0.3–1.3 km s−1, and the M ̇ in is about 10−3–10−4 M ⊙ yr−1, which is consistent with the results of intermediate or massive star formation in previous studies. The V in estimated from the Myers model is 0.1–1.6 km s−1, and the M ̇ in is within 10−3–10−5 M ⊙ yr−1. In addition, some identified infall sources show other star-forming activities, such as outflows and maser emissions. Especially for those sources with a double-peaked blue asymmetric profile, most of them have both infall and outflow evidence.

scholarly journals Magnetic fields and massive star formation

2018 ◽  
Vol 14 (A30) ◽  
pp. 141-141
Author(s):  
Qizhou Zhang
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Massive Star ◽  
Dense Core ◽  
Continuum Emission ◽  
Massive Star Formation ◽  
Stellar Objects ◽  
Star Forming ◽  
Dense Cores ◽  
The Mean

AbstractMassive stars ( ${\rm{M}} > \,8{M_ \odot }$ ) often form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. The role of magnetic fields during the formation of massive dense cores is still not clear. The steady improvement in sensitivity of (sub)millimeter interferometers over the past decade enabled observations of dust polarization of large samples of massive star formation regions. We carried out a polarimetric survey with the Submillimeter Array of 14 massive star forming clumps in continuum emission at a wavelength of 0.89 mm. This unprecedentedly large sample of massive star forming regions observed by a submillimeter interferometer before the advent of ALMA revealed compelling evidence of strong magnetic influence on the gas dynamics from 1 pc to 0.1 pc scales. We found that the magnetic fields in dense cores tend to be either parallel or perpendicular to the mean magnetic fields in their parental molecular clumps. Furthermore, the main axis of protostellar outflows does not appear to be aligned with the mean magnetic fields in the dense core where outflows are launched. These findings suggest that from 1 pc to 0.1 pc scales, magnetic fields are dynamically important in the collapse of clumps and the formation of dense cores. From the dense core scale to the accretion disk scale of ∼102 au, however, gravity and angular momentum appear to be more dominant relative to the magnetic field.

scholarly journals Dissecting a site of massive star formation: IRAS 23033+5951

2006 ◽  
Vol 2 (S237) ◽  
pp. 155-159
Author(s):  
Michael A. Reid ◽  
Brenda C. Matthews
Keyword(s):  
Star Formation ◽  
Velocity Gradient ◽  
Massive Star ◽  
Massive Star Formation ◽  
Star Forming ◽  
Geometric Center ◽  
Integrated Intensity ◽  
A Site

AbstractWe present new BIMA observations of the massive star-forming region IRAS 23033+5951 in Cepheus. 3 mm continuum observations reveal that the source decomposes into at least three dusty clumps, each of which has sufficient mass to form a massive star. The most massive clump has a mass of about 225 M and appears to house the massive protostar which drives the prominent CO outflow seen in the region. Our H13CN, 1-0, N2H+ 1-0, and H13CO+ 1-0 maps show that the three continuum sources are all embedded in an elongated structure whose long axis is perpendicular to the outflow. Both H13CO+ and H13CN peak at the geometric center of this structure, which lies between the two prominent continuum peaks. All three lines – H13CN, H13CO+, and N2H+ –show the same velocity gradient along the long axis of their integrated intensity maps. Although the approximately 90,000 AU length of the elongated structure prohibits a disk interpretation, the fact that the dynamical and gas masses of the structure differ by only a factor of a few suggests that the structure may be partially rotationally supported. We also detect a signature of infall toward the center of the structure, seen as an asymmetrically blue HCO+ line where its optically thin isotope, H13CO+, is symmetric and single-peaked.

scholarly journals Molecular cloud structure and star formation in the W43 complex

2012 ◽  
Vol 10 (H16) ◽  
pp. 592-592
Author(s):  
P. Carlhoff ◽  
P. Schilke ◽  
F. Motte ◽  
Q. Nguyen Luong
Keyword(s):  
Star Formation ◽  
Spectral Resolution ◽  
Total Mass ◽  
Column Density ◽  
Massive Star ◽  
High Spectral Resolution ◽  
Excitation Temperature ◽  
Star Forming ◽  
Star Forming Regions ◽  
Different Sources

AbstractThe W43 region is one of the most massive star forming regions in our Galaxy. It is subject to a large IRAM 30m project that observes high spectral resolution maps of the complete complex in the 13CO (2–1) and C18O (2–1) lines. We find a variety of different sources of which we calculate excitation temperature, H2 column density and mass. We find the total mass of dense clouds in the complex to be 1.2×106 M⊙.

scholarly journals IRAM and Gaia views of multi-episodic star formation in IC 1396A

2019 ◽  
Vol 622 ◽  
pp. A118 ◽  
Author(s):  
Aurora Sicilia-Aguilar ◽  
Nimesh Patel ◽  
Min Fang ◽  
Veronica Roccatagliata ◽  
Konstantin Getman ◽  
...  
Keyword(s):  
Star Formation ◽  
Column Density ◽  
Velocity Structure ◽  
Initial Conditions ◽  
Carbon Chain ◽  
Star Formation History ◽  
Evolutionary Stage ◽  
Star Forming ◽  
History Of ◽  
Continuum Data

Context. IC 1396A is a cometary globule that contains the Class 0 source IC 1396A-PACS-1, which was discovered with Herschel. Aims. We use IRAM 30m telescope and Gaia DR2 data to explore the star formation history of IC 1396A and investigate the possibilities of triggered star formation. Methods. IRAM and Herschel continuum data were used to obtain dust temperature and column density maps. Heterodyne data reveal the velocity structure of the gas. Gaia DR2 proper motions for the stars complete the kinematics of the region. Results. IC 1396A-PACS-1 presents molecular emission similar to a hot corino with warm carbon chain chemistry due to the UV irradiation. The source is embedded in a dense clump surrounded by gas at velocities that are significantly different from the velocities of the Tr 37 cluster. CN emission reveals photoevaporation, while continuum data and high-density tracers (C18O, HCO+, DCO+, and N2D+) reveal distinct gaseous structures with a range of densities and masses. Conclusions. By combining the velocity, column density, and temperature information and Gaia DR2 kinematics, we confirm that the globule has experienced various episodes of star formation. IC 1396A-PACS-1 is probably the last intermediate-mass protostar that will form within IC 1396A; it shows evidence of being triggered by radiation-driven implosion. Chemical signatures such as CCS place IC 1396A-PACS-1 among the youngest known protostars. Gaia DR2 data reveal velocities in the plane of the sky ~4 km s−1 for IC 1396A with respect to Tr 37. The total velocity difference (8 km s−1) between the Tr 37 cluster and IC 1396A is too small for IC 1396A to have undergone substantial rocket acceleration, which imposes constraints on the distance to the ionizing source in time and the possibilities of triggered star formation. The three stellar populations in the globule reveal that objects located within relatively close distances (<0.5 pc) can be formed in various star-forming episodes within ~1–2 Myr. Once the remaining cloud disperses, we expect substantial differences in evolutionary stage and initial conditions for the resulting objects and their protoplanetary disks, which may affect their evolution. Finally, evidence for short-range feedback from the embedded protostars, and in particular, the A-type star V390 Cep, is also observed.

scholarly journals H i imaging of dwarf star-forming galaxies: masses, morphologies, and gas deficiencies

2020 ◽  
Vol 498 (4) ◽  
pp. 4745-4789
Author(s):  
S Jaiswal ◽  
A Omar
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Surface Density ◽  
Column Density ◽  
Line Emission ◽  
Scaling Relations ◽  
Dwarf Star ◽  
Star Forming ◽  
Average Value ◽  
Tidal Interactions

ABSTRACT The Giant Meter-wave Radio Telescope observations of the H i 21 cm-line emission from 13 nearby dwarf star-forming galaxies are presented. These galaxies are selected from the catalogues of Wolf−Rayet galaxies having very young (≤10 Myr) star formation. The ranges of star formation rates and stellar masses of the sample galaxies are 0.03–1.7 M⊙ yr−1 and 0.04–22.3 × 108 M⊙, respectively. The H i line emission is detected from 12 galaxies with peak column density &gt;1 × 1021 cm−2. The 3σ H i column density sensitivities per channel width of 7 km s−1 for low (60 arcsec × 60 arcsec) resolution images are in the range 0.8–1.9 × 1019 cm−2. The H i channel images, moment images, global profiles, and mass surface density profiles are presented here. The average value of the peak H i mass surface density is estimated to be ∼2.5 M⊙ pc−2, which is significantly less compared to that in massive spiral galaxies. The scaling relations of $(M_{stars} + M_{\rm H\, I} + M_{\rm He})$versus Mdyn, gas fraction versus MB, $M_{\rm H\, I}$versus Mstars, H i-to-stellar mass ratio versus Mstars, and $M_{\rm H\, I}$versus $D_{\rm H\, I}$for the sample galaxies are estimated. These scaling relations can be used to constraint the key parameters in the galaxy evolution models. These galaxies are residing in group environment with galaxy density up to eight galaxy Mpc−3. An H i mass deficiency (with DEFH i &gt; 0.3) is noticed in majority of galaxies for their optical diameters as compared to galaxies in field environments. Clear signatures of tidal interactions in these galaxies could be inferred using the H i images. Isolated H i clouds without known optical counterparts are seen in the vicinity of several galaxies. H i emission envelope is found to be having an offset from the optical envelope in several galaxies. Consistent with the previous studies on galaxy evolution in group environments, tidal interactions seem to play an important role in triggering recent star formation.

scholarly journals Chandra and Spitzer observations of young clusters

2006 ◽  
Vol 2 (S237) ◽  
pp. 496-496
Author(s):  
S. J. Wolk ◽  
B. D. Spitzbart ◽  
T. L. Bourke
Keyword(s):  
Star Formation ◽  
Spectral Resolution ◽  
Massive Star ◽  
Young Star ◽  
Small Cluster ◽  
Massive Star Formation ◽  
X Ray ◽  
Star Forming ◽  
Be Star ◽  
Insight Into

AbstractThe combination of spatial and spectral resolution allow us to use Chandra in the study regions of massive star formation which had been inaccessible even from the ground until the last decade. IRAC and MIPS data from Spitzer can be combined with the X–ray data to provide insight into the presence of a disk and the activity of the star. The total package allows us to better understand the evolution of the clusters. We have an ongoing program to study several young star forming clusters including distant clusters between 1-3 kpc which support O stars, RCW 38, NGC 281 and RCW 108 and well as clusters within a kpc including IRAS 20050+2720 and NGC 1579, which is a small cluster centered on the Be star LkHα101 and is of uncertain distance although the X-ray data help us refine the current distance estimates. Given the space constraints we only discuss RCW 108 below.

scholarly journals ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – I. Survey description and a first look at G9.62+0.19

2020 ◽  
Vol 496 (3) ◽  
pp. 2790-2820 ◽  
Author(s):  
Tie Liu ◽  
Neal J Evans ◽  
Kee-Tae Kim ◽  
Paul F Goldsmith ◽  
Sheng-Yuan Liu ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Star Formation ◽  
Survey Data ◽  
Massive Star ◽  
High Mass ◽  
Dense Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Stellar Feedback ◽  
Dense Cores

ABSTRACT The ATOMS, standing for ALMA Three-millimeter Observations of Massive Star-forming regions, survey has observed 146 active star-forming regions with ALMA band 3, aiming to systematically investigate the spatial distribution of various dense gas tracers in a large sample of Galactic massive clumps, to study the roles of stellar feedback in star formation, and to characterize filamentary structures inside massive clumps. In this work, the observations, data analysis, and example science of the ATOMS survey are presented, using a case study for the G9.62+0.19 complex. Toward this source, some transitions, commonly assumed to trace dense gas, including CS J = 2−1, HCO+J = 1−0, and HCN J = 1−0, are found to show extended gas emission in low-density regions within the clump; less than 25 per cent of their emission is from dense cores. SO, CH3OH, H13CN, and HC3N show similar morphologies in their spatial distributions and reveal well the dense cores. Widespread narrow SiO emission is present (over ∼1 pc), which may be caused by slow shocks from large–scale colliding flows or H ii regions. Stellar feedback from an expanding H ii region has greatly reshaped the natal clump, significantly changed the spatial distribution of gas, and may also account for the sequential high-mass star formation in the G9.62+0.19 complex. The ATOMS survey data can be jointly analysed with other survey data, e.g. MALT90, Orion B, EMPIRE, ALMA_IMF, and ALMAGAL, to deepen our understandings of ‘dense gas’ star formation scaling relations and massive protocluster formation.

scholarly journals OB stars towards NGC 6357 and NGC 6334

2017 ◽  
Vol 12 (S330) ◽  
pp. 341-342
Author(s):  
Delphine Russeil
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Stellar Population ◽  
Proper Motions ◽  
Massive Star Formation ◽  
Ob Stars ◽  
Stellar Cluster ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ngc 6334

AbstractThe star forming regions NGC6334 and NGC6357 are amid the most active star-forming complexes of our Galaxy where massive star formation is occuring. Both complexes gather several HII regions but they exhibit different aspects: NGC6334 is characterised by a dense molecular ridge where recent massive star formation is obvious while NGC6357 is dominated by the action of the stellar cluster Pismis 24 which have shaped a large cavity. To understand and compare the formation of massive stars in these two regions requires to precise the distance and characterise the proper motions of the O to B3 stellar population in these regions.

scholarly journals The [O iii]+H β equivalent width distribution at z ≃ 7: implications for the contribution of galaxies to reionization

2020 ◽  
Vol 500 (4) ◽  
pp. 5229-5248
Author(s):  
Ryan Endsley ◽  
Daniel P Stark ◽  
Jacopo Chevallard ◽  
Stéphane Charlot
Keyword(s):  
Star Formation ◽  
Standard Deviation ◽  
Equivalent Width ◽  
Production Efficiency ◽  
Massive Star ◽  
Star Clusters ◽  
Strong Variation ◽  
Star Forming ◽  
Width Distribution ◽  
Intense Star Formation

ABSTRACT We quantify the distribution of [O iii]+H β line strengths at z ≃ 7 using a sample of 20 bright ($\mathrm{M}_{\mathrm{UV}}^{}$ ≲ –21) galaxies. We select these systems over wide-area fields (2.3 deg2 total) using a new colour-selection that precisely selects galaxies at z ≃ 6.63–6.83, a redshift range where blue Spitzer/IRAC [3.6]−[4.5] colours unambiguously indicate strong [O iii]+H β emission. These 20 galaxies suggest a lognormal [O iii]+H β EW distribution with median EW = 759$^{+112}_{-113}$ Å and standard deviation = 0.26$^{+0.06}_{-0.05}$ dex. We find no evidence for strong variation in this EW distribution with UV luminosity. The typical [O iii]+H β EW at z ≃ 7 implied by our sample is considerably larger than that in massive star-forming galaxies at z ≃ 2, consistent with a shift towards larger average sSFR (4.4 Gyr−1) and lower metallicities (0.16 Z⊙). We also find evidence for the emergence of a population with yet more extreme nebular emission ([O iii]+H β EW &gt; 1200 Å) that is rarely seen at lower redshifts. These objects have extremely large sSFR (&gt;30 Gyr−1), as would be expected for systems undergoing a burst or upturn in star formation. While this may be a short-lived phase, our results suggest that 20 per cent of the z ≃ 7 population has such extreme nebular emission, implying that galaxies likely undergo intense star formation episodes regularly at z &gt; 6. We argue that this population may be among the most effective ionizing agents in the reionization era, both in terms of photon production efficiency and escape fraction. We furthermore suggest that galaxies passing through this large sSFR phase are likely to be very efficient in forming bound star clusters.

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