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We present 850 $��$m polarimetric observations toward the Serpens Main molecular cloud obtained using the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields In STar-forming Region Observations (BISTRO) survey. These observations probe the magnetic field morphology of the Serpens Main molecular cloud on about 6000 au scales, which consists of cores and six filaments with different physical properties such as density and star formation activity. Using the histogram of relative orientation (HRO) technique, we find that magnetic fields are parallel to filaments in less dense filamentary structures where $N_{H_2} < 0.93\times 10^{22}$ cm$^{-2}$ (magnetic fields perpendicular to density gradients), while being perpendicular to filaments (magnetic fields parallel to density gradients) in dense filamentary structures with star formation activity. Moreover, applying the HRO technique to denser core regions, we find that magnetic field orientations change to become perpendicular to density gradients again at $N_{H_2} \approx 4.6 \times 10^{22}$ cm$^{-2}$. This can be interpreted as a signature of core formation. At $N_{H_2} \approx 16 \times 10^{22}$ cm$^{-2}$ magnetic fields change back to being parallel to density gradients once again, which can be understood to be due to magnetic fields being dragged in by infalling material. In addition, we estimate the magnetic field strengths of the filaments ($B_{POS} = 60-300~��$G)) using the Davis-Chandrasekhar-Fermi method and discuss whether the filaments are gravitationally unstable based on magnetic field and turbulence energy densities., 18 pages, accepted for publication in ApJ

Tao-Chung Ching et al., We present 850 μm dust polarization observations of the massive DR21 filament from the B-fields In STar-forming Region Observations (BISTRO) survey, using the POL-2 polarimeter and the SCUBA-2 camera on the James Clerk Maxwell Telescope. We detect ordered magnetic fields perpendicular to the parsec-scale ridge of the DR21 main filament. In the subfilaments, the magnetic fields are mainly parallel to the filamentary structures and smoothly connect to the magnetic fields of the main filament. We compare the POL-2 and Planck dust polarization observations to study the magnetic field structures of the DR21 filament on 0.1–10 pc scales. The magnetic fields revealed in the Planck data are well-aligned with those of the POL-2 data, indicating a smooth variation of magnetic fields from large to small scales. The plane-of-sky magnetic field strengths derived from angular dispersion functions of dust polarization are 0.6–1.0 mG in the DR21 filament and ∼0.1 mG in the surrounding ambient gas. The mass-to-flux ratios are found to be magnetically supercritical in the filament and slightly subcritical to nearly critical in the ambient gas. The alignment between column density structures and magnetic fields changes from random alignment in the low-density ambient gas probed by Planck to mostly perpendicular in the high-density main filament probed by James Clerk Maxwell Telescope. The magnetic field structures of the DR21 filament are in agreement with MHD simulations of a strongly magnetized medium, suggesting that magnetic fields play an important role in shaping the DR21 main filament and subfilaments., This work is supported by National Natural Science Foundation of China (NSFC) grant Nos. 11988101, U1931117, 11725313, and 12073061 and the CAS International Partnership Program of Chinese Academy of Sciences grant No. 114A11KYSB20160008. T.-C.C. is funded by Chinese Academy of Sciences Taiwan Young Talent Program grant No. 2018TW2JB0002. T.-C.C. and C.E. were supported by Special Funding for Advanced Users, budgeted and administrated by Center for Astronomical Mega-Science (CAMS), Chinese Academy of Sciences. K.P. is a Royal Society University Research Fellow, supported by grant No. URF\R1\211322. D.J. is supported by the National Research Council of Canada and by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant. P.M.K. is supported by the Ministry of Science and Technology (MoST) in Taiwan through grants 109-2112-M-001-022 and 110-2112-M-001-057. C.W.L. is supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2019R1A2C1010851), and by the Korea Astronomy and Space Science Institute grant funded by the Korea government (MSIT; Project No. 2022-1-840-05). T.H. is supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) through the Mid-career Research Program (2019R1A2C1087045). W.K. was supported by the NRF grant funded by the MSIT (2021R1F1A1061794). C.E. acknowledges the financial support from grant RJF/2020/000071 as a part of Ramanujan Fellowship awarded by the Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Govt. of India. F.P. acknowledges support from the Spanish State Research Agency (AEI) under grant No. PID2019-105552RB-C43. M.T. is supported by JSPS KAKENHI grant Nos. 18H05442, 15H02063, and 22000005. J.K. is supported by JSPS KAKENHI grant No. 19K14775. L.F. and F.K. acknowledge the support by the MoST in Taiwan through grant 107-2119-M-001-031-MY3 and Academia Sinica through grant AS-IA-106-M03. L.F. acknowledges the support by the MoST in Taiwan through grants 111-2811-M-005-007 and 109-2112-M-005-003-MY3. C.L.H.H. acknowledges the support of the NAOJ Fellowship and JSPS KAKENHI grants 18K13586 and 20K14527. F.K. is supported by the Spanish program Unidad de Excelencia María de Maeztu CEX2020-001058-M, financed by MCIN/AEI/10.13039/501100011033. K.Q. is partially supported by National Key R&D Program of China No. 2022YFA1603100, and acknowledges the National Natural Science Foundation of China (NSFC) grant U1731237. S.P.L. acknowledges grants from the Ministry of Science and Technology of Taiwan 106-2119-M-007-021-MY3 and 109-2112-M-007-010-MY3. Y.D. acknowledges the support of JSPS KAKENHI grants 25247016 and 18H01250. Y.S.D. is supported by the National Key R&D Program of China for grant No. 2022YFA1605300, and NSFC grants Nos. 12273051, 11933003.

Hwang et al., We present and analyze observations of polarized dust emission at 850 μm toward the central 1 × 1 pc hub-filament structure of Monoceros R2 (Mon R2). The data are obtained with SCUBA-2/POL-2 on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields in Star-forming Region Observations survey. The orientations of the magnetic field follow the spiral structure of Mon R2, which are well described by an axisymmetric magnetic field model. We estimate the turbulent component of the magnetic field using the angle difference between our observations and the best-fit model of the underlying large-scale mean magnetic field. This estimate is used to calculate the magnetic field strength using the Davis–Chandrasekhar–Fermi method, for which we also obtain the distribution of volume density and velocity dispersion using a column density map derived from Herschel data and the C18O (J = 3 − 2) data taken with HARP on the JCMT, respectively. We make maps of magnetic field strengths and mass-to-flux ratios, finding that magnetic field strengths vary from 0.02 to 3.64 mG with a mean value of 1.0 ± 0.06 mG, and the mean critical mass-to-flux ratio is 0.47 ± 0.02. Additionally, the mean Alfvén Mach number is 0.35 ± 0.01. This suggests that, in Mon R2, the magnetic fields provide resistance against large-scale gravitational collapse, and the magnetic pressure exceeds the turbulent pressure. We also investigate the properties of each filament in Mon R2. Most of the filaments are aligned along the magnetic field direction and are magnetically subcritical., J.H. is supported by the University of Science and Technology (UST) Overseas Training Program 2022, funded by the University of Science and Technology, Korea (No. 2022-017). K.P. is a Royal Society University Research Fellow, supported by grant number URF\R1\211322. C.W.L. was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF- 2019R1A2C1010851), and by the Korea Astronomy and Space Science Institute grant funded by the Korea government (MSIT; Project No. 2022-1-840-05). D.J. and J.d.F. are supported by the National Research Council of Canada and by Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants. G.P. is supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF; 2020R1A6A3A01100208) W.K. was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT; NRF-2021R1F1A1061794). M.T. is supported by JSPS KAKENHI grant Nos. 18H05442, 15H02063, and 22000005. J.K. is supported by JSPS KAKENHI grant No. 19K14775. M.M. is supported by JSPS KAKENHI grant No. 20K03276. F.P. acknowledges support from the Spanish State Research Agency Agencia Estatal de Investigación (AEI) under grant number PID2019-105552RB-C43. S.P.L., H.Y.D., S.J.L., and M.Z.Y. acknowledge grants from the Ministry of Science and Technology of Taiwan 106-2119-M-007-021-MY3 and 109-2112-M-007-010-MY3. C.E. acknowledges the financial support from grant RJF/2020/000071 as a part of a Ramanujan Fellowship awarded by Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Govt. of India. L.F. and F.K. acknowledge support from the Ministry of Science and Technology of Taiwan, under grant No. MoST107-2119-M-001-031- MY3 and from Academia Sinica under grant No. AS-IA-106-M03. L.F. acknowledges the support by the MoST in Taiwan through grants 111-2811-M-005-007 and 109-2112-M-005-003-MY3. F.K. acknowledges support from the Spanish program Unidad de Excelencia María de Maeztu CEX2020-001058-M, financed by MCIN/AEI/10.13039/501100011033. Y.S.D. would like to acknowledge the support from NSFC grants 12273051 and 10878003. M.R. is supported by the international Gemini Observatory, a program of NSFs NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini partnership of Argentina, Brazil, Canada, Chile, the Republic of Korea, and the United States of America. The JCMT is operated by the East Asian Observatory on behalf of The National Astronomical Observatory of Japan; Academia Sinica Institute of Astronomy and Astrophysics; the Korea Astronomy and Space Science Institute; the Operation, Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments, budgeted from the Ministry of Finance of China. Additional funding support is provided by the Science and Technology Facilities Council of the United Kingdom and participating universities and organizations in the United Kingdom, Canada, and Ireland. Additional funds for the construction of SCUBA-2 were provided by the Canada Foundation for Innovation.

We present the results of simultaneous 450 $\mu$m and 850 $\mu$m polarization observations toward the massive star forming region NGC 2071IR, a target of the BISTRO (B-fields in Star-Forming Region Observations) Survey, using the POL-2 polarimeter and SCUBA-2 camera mounted on the James Clerk Maxwell Telescope. We find a pinched magnetic field morphology in the central dense core region, which could be due to a rotating toroidal disk-like structure and a bipolar outflow originating from the central young stellar object, IRS 3. Using the modified Davis-Chandrasekhar-Fermi method, we obtain a plane-of-sky magnetic field strength of 563$\pm$421 $\mu$G in the central $\sim$0.12 pc region from 850 $\mu$m polarization data. The corresponding magnetic energy density of 2.04$\times$10$^{-8}$ erg cm$^{-3}$ is comparable to the turbulent and gravitational energy densities in the region. We find that the magnetic field direction is very well aligned with the whole of the IRS 3 bipolar outflow structure. We find that the median value of polarization fractions, 3.0 \%, at 450 $\mu$m in the central 3 arcminute region, which is larger than the median value of 1.2 \% at 850 $\mu$m. The trend could be due to the better alignment of warmer dust in the strong radiation environment. We also find that polarization fractions decrease with intensity at both wavelengths, with slopes, determined by fitting a Rician noise model, of $0.59 \pm 0.03$ at 450 $\mu$m and $0.36 \pm 0.04$ at 850 $\mu$m, respectively. We think that the shallow slope at 850 $\mu$m is due to grain alignment at the center being assisted by strong radiation from the central young stellar objects., Comment: 17 pages, 11 figures, 4 tables

We have obtained sensitive dust continuum polarization observations at 850 μm in the B213 region of Taurus using POL-2 on SCUBA-2 at the James Clerk Maxwell Telescope as part of the B-fields in STar-forming Region Observations (BISTRO) survey. These observations allow us to probe magnetic field (B-field) at high spatial resolution (∼2000 au or ∼0.01 pc at 140 pc) in two protostellar cores (K04166 and K04169) and one prestellar core (Miz-8b) that lie within the B213 filament. Using the Davis–Chandrasekhar–Fermi method, we estimate the B-field strengths in K04166, K04169, and Miz-8b to be 38 ± 14, 44 ± 16, and 12 ± 5 μG, respectively. These cores show distinct mean B-field orientations. The B-field in K04166 is well ordered and aligned parallel to the orientations of the core minor axis, outflows, core rotation axis, and large-scale uniform B-field, in accordance with magnetically regulated star formation via ambipolar diffusion taking place in K04166. The B-field in K04169 is found to be ordered but oriented nearly perpendicular to the core minor axis and large-scale B-field and not well correlated with other axes. In contrast, Miz-8b exhibits a disordered B-field that shows no preferred alignment with the core minor axis or large-scale field. We found that only one core, K04166, retains a memory of the large-scale uniform B-field. The other two cores, K04169 and Miz-8b, are decoupled from the large-scale field. Such a complex B-field configuration could be caused by gas inflow onto the filament, even in the presence of a substantial magnetic flux.

We present the star formation rates (SFRs) of galaxies with redshifts of 0 < $z$ < 6 and cosmic star formation rate densities as a function of redshift. The SFRs for the galaxies at infrared emission have been investigated for 1752 sources from the Spitzer 70 μm observations of the Spitzer COSMOS Legacy survey and the various surveys in the literature. Analyzing the SFRs of these objects provides the distribution of SFRs across the redshift range. We have derived the star formation rate densities (SFRDs) based on the present analysis of SFRs and comoving volume calculated from the cosmic parameters we have used. Our results show a slightly steeper slope at lower and intermediate redshift, 0 < $z$ < 2. We have found a steep decline of SFRD from $z=1$ to 0, but measured a peak of SFRD at $z\approx 2.2-2.4$ .

Prestellar cores are self-gravitating dense and cold structures within molecular clouds where future stars are born. They are expected, at the stage of transitioning to the protostellar phase, to harbor centrally concentrated dense (sub)structures that will seed the formation of a new star or the binary/multiple stellar systems. Characterizing this critical stage of evolution is key to our understanding of star formation. In this work, we report the detection of high-density (sub)structures on the thousand-astronomical-unit (au) scale in a sample of dense prestellar cores. Through our recent ALMA observations toward the Orion Planck Galactic Cold Clumps, we have found five extremely dense prestellar cores, which have centrally concentrated regions of ∼2000 au in size, and several 107 cm-3 in average density. Masses of these centrally dense regions are in the range of 0.30 to 6.89M⊙. For the first time, our higher resolution observations (0.8' ∼ 320 au) further reveal that one of the cores shows clear signatures of fragmentation; such individual substructures/fragments have sizes of 800-1700 au, masses of 0.08 to 0.84M⊙, densities of 2 - 8 × 107 cm-3, and separations of ∼1200 au. The substructures are massive enough (≳0.1M⊙) to form young stellar objects and are likely examples of the earliest stage of stellar embryos that can lead to widely (∼1200 au) separated multiple systems., L. acknowledges the support from the international partnership program of the Chinese Academy of Sciences through grant No.114231KYSB20200009, National Natural Science Foundation of China (NSFC) through grant NSFC No.12073061, and Shanghai Pujiang Program 20PJ1415500. N.H. acknowledges MoST 108-2112-M-001-017 and MoST 109-2112-M-001-023 grants. G.G. acknowledges support from ANID project AFB 170002. L.B. acknowledges support from ANID project AFB-170002. S.L.Q. is supported by the National Natural Science Foundation of China under grant No. U1631237. D.J. is supported by NRC Canada and by an NSERC Discovery Grant. V.M.P. acknowledges support by the Spanish MINECO under project AYA2017-88754-P, and financial support from the State Agency for Research of the Spanish Ministry of Science and Innovation through the “Unit of Excellence María de Maeztu 2020-2023” award to the Institute of Cosmos Sciences (CEX2019-000918-M). C.W.L. is supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2019R1A2C1010851). A.S. acknowledges financial support from the NSF through grant AST-1715876. The research was carried out in part at the Jet Propulsion Laboratory, which is operated for NASA by the California Institute of Technology. D. L. acknowledges support from NSFC No. 11911530226 and 11725313. K.T. was supported by JSPS KAKENHI grant No. 20H05645. J.H. thanks the NSFC grant No. 11873086 and Yunnan Province of China (No. 2017HC018).This work is sponsored (in part) by the Chinese Academy of Sciences (CAS), through a grant to the CAS South America Center for Astronomy (CASSACA) in Santiago, Chile.

Gas at high Galactic latitude is a relatively little-noticed component of the interstellar medium. In an effort to address this, forty-one Planck Galactic Cold Clumps at high Galactic latitude (HGal; $|b|>25^{\circ}$) were observed in $^{12}$CO, $^{13}$CO and C$^{18}$O J=1-0 lines, using the Purple Mountain Observatory 13.7-m telescope. $^{12}$CO (1-0) and $^{13}$CO (1-0) emission was detected in all clumps while C$^{18}$O (1-0) emission was only seen in sixteen clumps. The highest and average latitudes are $71.4^{\circ}$ and $37.8^{\circ}$, respectively. Fifty-one velocity components were obtained and then each was identified as a single clump. Thirty-three clumps were further mapped at 1$^\prime$ resolution and 54 dense cores were extracted. Among dense cores, the average excitation temperature $T_{\mathrm{ex}}$ of $^{12}$CO is 10.3 K. The average line widths of thermal and non-thermal velocity dispersions are $0.19$ km s$^{-1}$ and $0.46$ km s$^{-1}$ respectively, suggesting that these cores are dominated by turbulence. Distances of the HGal clumps given by Gaia dust reddening are about $120-360$ pc. The ratio of $X_{13}$/$X_{18}$ is significantly higher than that in the solar neighbourhood, implying that HGal gas has a different star formation history compared to the gas in the Galactic disk. HGal cores with sizes from $0.01-0.1$ pc show no notable Larson's relation and the turbulence remains supersonic down to a scale of slightly below $0.1$ pc. None of the HGal cores which bear masses from 0.01-1 $M_{\odot}$ are gravitationally bound and all appear to be confined by outer pressure., 35 pages, 13 figures

Ten protostellar outflows in the Orion molecular clouds were mapped in the $^{12}$CO/$^{13}$CO ${J=6\rightarrow5}$ and $^{12}$CO ${J=7\rightarrow6}$ lines. The maps of these mid-$J$ CO lines have an angular resolution of about 10$''$ and a typical field size of about 100$''$. Physical parameters of the molecular outflows were derived, including mass transfer rates, kinetic luminosities, and outflow forces. The outflow sample was expanded by re-analyzing archival data of nearby low-luminosity protostars, to cover a wide range of bolometric luminosities. Outflow parameters derived from other transitions of CO were compared. The mid-$J$ ($J_{\rm up} \approx 6$) and low-$J$ ($J_{\rm up} \leq 3$) CO line wings trace essentially the same outflow component. By contrast, the high-$J$ (up to $J_{\rm up} \approx 50$) line-emission luminosity of CO shows little correlation with the kinetic luminosity from the ${J=6\rightarrow5}$ line, which suggests that they trace distinct components. The low/mid-$J$ CO line wings trace long-term outflow behaviors while the high-$J$ CO lines are sensitive to short-term activities. The correlations between the outflow parameters and protostellar properties are presented, which shows that the strengths of molecular outflows increase with bolometric luminosity and envelope mass., Comment: 31 pages, 16 figures, Accepted for publication in ApJS

We report the first high spatial resolution measurement of magnetic fields surrounding LkH$\alpha$ 101, a part of the Auriga-California molecular cloud. The observations were taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope within the framework of the B-fields In Star-forming Region Observations (BISTRO) survey. Observed polarization of thermal dust emission at 850 $\mu$m is found to be mostly associated with the red-shifted gas component of the cloud. The magnetic field displays a relatively complex morphology. Two variants of the Davis-Chandrasekhar-Fermi method, unsharp masking and structure function, are used to calculate the strength of magnetic fields in the plane of the sky, yielding a similar result of $B_{\rm POS}\sim 115$ $\mathrm{\mu}$G. The mass-to-magnetic-flux ratio in critical value units, $\lambda\sim0.3$, is the smallest among the values obtained for other regions surveyed by POL-2. This implies that the LkH$\alpha$ 101 region is sub-critical and the magnetic field is strong enough to prevent gravitational collapse. The inferred $\delta B/B_0\sim 0.3$ implies that the large scale component of the magnetic field dominates the turbulent one. The variation of the polarization fraction with total emission intensity can be fitted by a power-law with an index of $\alpha=0.82\pm0.03$, which lies in the range previously reported for molecular clouds. We find that the polarization fraction decreases rapidly with proximity to the only early B star (LkH$\alpha$ 101) in the region. The magnetic field tangling and the joint effect of grain alignment and rotational disruption by radiative torques are potential of explaining such a decreasing trend., Comment: 25 pages, 19 figures, Accepted for publication in The Astrophysical Journal

Planck Galactic Cold Clumps (PGCCs) are contemplated to be the ideal targets to probe the early phases of star formation. We have conducted a survey of 72 young dense cores inside PGCCs in the Orion complex with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3\,mm (band 6) using three different configurations (resolutions $\sim$ 0$\farcs$35, 1$\farcs$0, and 7$\farcs$0) to statistically investigate their evolutionary stages and sub-structures. We have obtained images of the 1.3\,mm continuum and molecular line emission ($^{12}$CO, and SiO) at an angular resolution of $\sim$ 0$\farcs$35 ($\sim$ 140\,au) with the combined arrays. We find 70 substructures within 48 detected dense cores with median dust-mass $\sim$ 0.093\,M$_{\sun}$ and deconvolved size $\sim$ 0$\farcs$27. Dense substructures are clearly detected within the central 1000\,au of four candidate prestellar cores. The sizes and masses of the substructures in continuum emission are found to be significantly reduced with protostellar evolution from Class\,0 to Class\,I. We also study the evolutionary change in the outflow characteristics through the course of protostellar mass accretion. A total of 37 sources exhibit CO outflows, and 20 ($>$50\%) show high-velocity jets in SiO. The CO velocity-extents ($\Delta$Vs) span from 4 to 110 km/s with outflow cavity opening angle width at 400\,au ranging from $[\Theta_{obs}]_{400}$ $\sim$ 0$\farcs$6 to 3$\farcs$9, which corresponds to 33$\fdg$4$-$125$\fdg$7. For the majority of the outflow sources, the $\Delta$Vs show a positive correlation with $[\Theta_{obs}]_{400}$, suggesting that as protostars undergo gravitational collapse, the cavity opening of a protostellar outflow widens and the protostars possibly generate more energetic outflows., Comment: 43 pages, 25 figures (14 in the main text, 9 in the appendix), accepted for publication in the Astrophysical Journal Supplement Series (ApJS)

We present new observations of the active star formation region NGC 1333 in the Perseus molecular cloud complex from the James Clerk Maxwell Telescope B -Fields In Star-forming Region Observations (BISTRO) survey with the POL-2 instrument. The BISTRO data cover the entire NGC 1333 complex (∼1.5 pc × 2 pc) at 0.02 pc resolution and spatially resolve the polarized emission from individual filamentary structures for the first time. The inferred magnetic field structure is complex as a whole, with each individual filament aligned at different position angles relative to the local field orientation. We combine the BISTRO data with low- and high- resolution data derived from Planck and interferometers to study the multiscale magnetic field structure in this region. The magnetic field morphology drastically changes below a scale of ∼1 pc and remains continuous from the scales of filaments (∼0.1 pc) to that of protostellar envelopes (∼0.005 pc or ∼1000 au). Finally, we construct simple models in which we assume that the magnetic field is always perpendicular to the long axis of the filaments. We demonstrate that the observed variation of the relative orientation between the filament axes and the magnetic field angles are well reproduced by this model, taking into account the projection effects of the magnetic field and filaments relative to the plane of the sky. These projection effects may explain the apparent complexity of the magnetic field structure observed at the resolution of BISTRO data toward the filament network., Erratum published in volume 899, issue 1, 5 p., April 10 2021. DOI: 10.3847/1538-4357/abf2b3

We mapped two molecular cloud cores in the Orion A cloud with the ALMA ACA 7-m Array and with the Nobeyama 45-m radio telescope. These cores have bright N$_2$D$^+$ emission in single-pointing observations with the Nobeyama 45-m radio telescope, have relatively high deuterium fraction, and are thought to be close to the onset of star formation. One is a star-forming core, and the other is starless. These cores are located along filaments observed in N$_2$H$^+$, and show narrow linewidths of 0.41 km s$^{-1}$ and 0.45 km s$^{-1}$ in N$_2$D$^+$, respectively, with the Nobeyama 45-m telescope. Both cores were detected with the ALMA ACA 7m Array in the continuum and molecular lines at Band 6. The starless core G211 shows clumpy structure with several sub-cores, which in turn show chemical differences. Also, the sub-cores in G211 have internal motions that are almost purely thermal. The starless sub-core G211D, in particular, shows a hint of the inverse P Cygni profile, suggesting infall motion. The star-forming core G210 shows an interesting spatial feature of two N$_2$D$^+$ peaks of similar intensity and radial velocity located symmetrically with respect to the single dust continuum peak. One interpretation is that the two N$_2$D$^+$ peaks represent an edge-on pseudo-disk. The CO outflow lobes, however, are not directed perpendicular to the line connecting both N$_2$D$^+$ peaks., 31 pages, 17 figures, 9 tables, to appear in ApJ (accepted April 23, 2020)

The CS molecule is known to be absorbed onto dust in the cold and dense conditions, causing it to get significantly depleted in the central region of cores. This study is aimed to investigate the depletion of the CS molecule using the optically thin C$^{34}$S molecular line observations. We mapped five prestellar cores, L1544, L1552, L1689B, L694-2, and L1197 using two molecular lines, C$^{34}$S $(J=2-1)$ and N$_2$H$^+$ $(J=1-0)$ with the NRO 45-m telescope, doubling the number of cores where the CS depletion was probed using C$^{34}$S. In most of our targets, the distribution of C$^{34}$S emission shows features that suggest that the CS molecule is generally depleted in the center of the prestellar cores. The radial profile of the CS abundance with respect to H$_2$ directly measured from the CS emission and the Herschel dust emission indicates that the CS molecule is depleted by a factor of $\sim$3 toward the central regions of the cores with respect to their outer regions. The degree of the depletion is found to be even more enhanced by an order of magnitude when the contaminating effect introduced by the presence of CS molecules in the surrounding envelope that lie along the line-of-sight is removed. Except for L1197 which is classified as relatively the least evolved core in our targets based on its observed physical parameters, we found that the remaining four prestellar cores are suffering from significant CS depletion at their central region regardless of the relative difference in their evolutionary status., 20 pages, 9 figures, Accepted for publication in ApJ

We present the results of a single-pointing survey of 207 dense cores embedded in Planck Galactic Cold Clumps distributed in five different environments ($\lambda$ Orionis, Orion A, B, Galactic plane, and high latitudes) to identify dense cores on the verge of star formation for the study of the initial conditions of star formation. We observed these cores in eight molecular lines at 76-94 GHz using the Nobeyama 45-m telescope. We find that early-type molecules (e.g., CCS) have low detection rates and that late-type molecules (e.g., N$_2$H$^+$, c-C$_3$H$_2$) and deuterated molecules (e.g., N$_2$D$^+$, DNC) have high detection rates, suggesting that most of the cores are chemically evolved. The deuterium fraction (D/H) is found to decrease with increasing distance, indicating that it suffers from differential beam dilution between the D/H pair of lines for distant cores ($>$1 kpc). For $\lambda$ Orionis, Orion A, and B located at similar distances, D/H is not significantly different, suggesting that there is no systematic difference in the observed chemical properties among these three regions. We identify at least eight high D/H cores in the Orion region and two at high latitudes, which are most likely to be close to the onset of star formation. There is no clear evidence of the evolutionary change in turbulence during the starless phase, suggesting that the dissipation of turbulence is not a major mechanism for the beginning of star formation as judged from observations with a beam size of 0.04 pc., Comment: 55 pages, 12 Figures, 8 Tables, accepted for publication in ApJS

[Abridged] Filaments and hubs have received special attention recently thanks to studies showing their role in star formation. While the column density and velocity structures of both filaments and hubs have been studied, their magnetic fields (B-field) are not yet characterized. We aim to understand the role of the B-field in the dynamical evolution of the NGC 6334 hub-filament network. We present new observations of the dust polarized emission at 850$\mu$m towards NGC 6334 obtained with the JCMT/POL-2. We study the distribution and dispersion of the polarized intensity ($PI$), the polarization fraction ($PF$), and the B-field angle ($\theta_{B}$). We derive the power spectrum of the intensity and $\theta_{B}$ along the ridge crest. Our analyses show a complex B-field structure when observed over the whole region ($\sim10$ pc), however, at smaller scales ($\sim1$ pc), $\theta_{B}$ varies coherently along the filaments. The observed power spectrum of $\theta_{B}$ can be well represented with a power law function with a slope $-1.33\pm0.23$, which is $\sim20\%$ shallower than that of $I$. This result is compatible with the properties of simulated filaments and may indicate the processes at play in the formation of filaments. $\theta_{B}$ rotates from being mostly perpendicular to the filament crests to mostly parallel as they merge with the hubs. This variation of $\theta_{B}$ may be tracing local velocity flows of matter in-falling onto the hubs. Our analysis suggests a variation of the energy balance along the crests of these filaments, from magnetically critical/supercritical at their far ends to magnetically subcritical near the hubs. We detect an increase of $PF$ towards the high-column density star cluster-forming hubs that may result from the increase of grain alignment efficiency due to stellar radiation from the newborn stars., Comment: Accepted for publication in Astronomy & Astrophysics

The Planck Catalogue of Galactic Cold Clumps provides an all-sky sample of potential star-forming regions based on the submillimeter emission of their dust content. Around 1000 of these Planck objects were mapped with the James Clerk Maxwell telescope in the submillimeter range during the SCOPE survey, identifying prestellar and protostellar dense clumps inside them. We used the Effelsberg 100 m telescope to observe the emission lines of the NH3 inversion transitions toward a sample of 97 dense objects in varying environments in order to assess the physical parameters of their gas content. We derive their temperature, density, and velocity dispersion, correlating the resulting parameters with the environmental and evolutionary characteristics of the targets and with regard to their distance and physical size. We examine the dependence of physical parameters on distance and Galactic position and compare the gas-based and dust-continuum-based temperatures and densities. Together with the presence of maser emission and higher inversion transitions of ammonia, we may differentiate between certain groups of targets, e.g., filamentary, protostellar clumps, and high-latitude, core-sized, starless sources.

L1521F is found to be forming multiple cores and it is cited as an example of the densest core with an embedded VeLLO in a highly dynamical environment. We present the core-scale magnetic fields (B-fields) in the near vicinity of the VeLLO L1521F-IRS using submm polarization measurements at 850$~\mu$m using JCMT POL-2. This is the first attempt to use high-sensitivity observations to map the sub-parsec scale B-fields in a core with a VeLLO. The B-fields are ordered and very well connected to the parsec-scale field geometry seen in our earlier optical polarization observations and the large-scale structure seen in Planck dust polarization. The core scale B-field strength estimated using Davis-Chandrasekhar-Fermi relation is $\rm 330\pm100~\mu$G which is more than ten times of the value we obtained in the envelope (envelope in this paper is "core envelope"). This indicates that B-fields are getting stronger on smaller scales. The magnetic energies are found to be 1 to 2 orders of magnitude higher than non-thermal kinetic energies in the envelope and core. This suggests that magnetic fields are more important than turbulence in the energy budget of L1521F. The mass-to-flux ratio of 2.3$\pm$0.7 suggests that the core is magnetically-supercritical. The degree of polarization is steadily decreasing towards the denser part of the core with a power law slope of -0.86., Comment: 12 pages, 5 figures, accepted for publication in ApJ

We present the first release of the data and compact-source catalogue for the JCMT Large Program SCUBA-2 Continuum Observations of Pre-protostellar Evolution (SCOPE). SCOPE consists of 850-um continuum observations of 1235 Planck Galactic Cold Clumps (PGCCs) made with the Submillimetre Common-User Bolometer Array 2 on the James Clerk Maxwell Telescope. These data are at an angular resolution of 14.4 arcsec, significantly improving upon the 353-GHz resolution of Planck at 5 arcmin, and allowing for a catalogue of 3528 compact sources in 558 PGCCs. We find that the detected PGCCs have significant sub-structure, with 61 per cent of detected PGCCs having 3 or more compact sources, with filamentary structure also prevalent within the sample. A detection rate of 45 per cent is found across the survey, which is 95 per cent complete to Planck column densities of $N_{H_{2}}$ $>$ 5 $\times$ 10$^{21}$ cm$^{-2}$. By positionally associating the SCOPE compact sources with YSOs, the star formation efficiency, as measured by the ratio of luminosity to mass, in nearby clouds is found to be similar to that in the more distant Galactic Plane, with the column density distributions also indistinguishable from each other., 16 pages, 13 figures, 1 table. Accepted for publication in MNRAS

We present the 850 $\mu$m polarization observations toward the IC5146 filamentary cloud taken using the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) and its associated polarimeter (POL-2), mounted on the James Clerk Maxwell Telescope (JCMT), as part of the B-fields In STar forming Regions Observations (BISTRO). This work is aimed at revealing the magnetic field morphology within a core-scale ($\lesssim 1.0$ pc) hub-filament structure (HFS) located at the end of a parsec-scale filament. To investigate whether or not the observed polarization traces the magnetic field in the HFS, we analyze the dependence between the observed polarization fraction and total intensity using a Bayesian approach with the polarization fraction described by the Rice likelihood function, which can correctly describe the probability density function (PDF) of the observed polarization fraction for low signal-to-noise ratio (SNR) data. We find a power-law dependence between the polarization fraction and total intensity with an index of 0.56 in $A_V\sim$ 20--300 mag regions, suggesting that the dust grains in these dense regions can still be aligned with magnetic fields in the IC5146 regions. Our polarization maps reveal a curved magnetic field, possibly dragged by the contraction along the parsec-scale filament. We further obtain a magnetic field strength of 0.5$\pm$0.2 mG toward the central hub using the Davis-Chandrasekhar-Fermi method, corresponding to a mass-to-flux criticality of $\sim$ $1.3\pm0.4$ and an Alfv\'{e}nic Mach number of $, Comment: 24 pages, 15 figures, accepted for publication in ApJ

"TRAO FUNS" is a project to survey Gould Belt's clouds in molecular lines. This paper presents its first results on the central region of the California molecular cloud, L1478. We performed On-The-Fly mapping observations using the Taedeok Radio Astronomy Observatory (TRAO) 14m single dish telescope equipped with a 16 multi-beam array covering $\sim$1.0 square degree area of this region using C$^{18}$O (1-0) mainly tracing low density cloud and about 460 square arcminute area using N$_{2}$H$^{+}$ (1-0) mainly tracing dense cores. CS (2-1) and SO $(3_{2}-2_{1})$ were also used simultaneously to map $\sim$440 square arcminute area of this region. We identified 10 filaments by applying the dendrogram technique to the C$^{18}$O data-cube and 8 dense N$_{2}$H$^{+}$ cores by using {\sc FellWalker}. Basic physical properties of filaments such as mass, length, width, velocity field, and velocity dispersion are derived. It is found that L1478 consists of several filaments with slightly different velocities. Especially the filaments which are supercritical are found to contain dense cores detected in N$_{2}$H$^{+}$. Comparison of non-thermal velocity dispersions derived from C$^{18}$O and N$_{2}$H$^{+}$ for the filaments and dense cores indicates that some of dense cores share similar kinematics with those of the surrounding filaments while several dense cores have different kinematics with those of their filaments. This suggests that the formation mechanism of dense cores and filaments can be different in individual filaments depending on their morphologies and environments., Comment: 25 pages, 15 figures, accepted for publication in ApJ

We present the B-fields mapped in IRDC G34.43+0.24 using 850\,$\mu$m polarized dust emission observed with the POL-2 instrument at JCMT. We examine the magnetic field geometries and strengths in the northern, central, and southern regions of the filament. The overall field geometry is ordered and aligned closely perpendicular to the filament's main axis, particularly in regions containing the central clumps MM1 and MM2, whereas MM3 in the north has field orientations aligned with its major axis. The overall field orientations are uniform at large (POL-2 at 14$\arcsec$ and SHARP at 10$\arcsec$) to small scales (TADPOL at 2.5$\arcsec$ and SMA at 1.5$\arcsec$) in the MM1 and MM2 regions. SHARP/CSO observations in MM3 at 350\,$\mu$m from Tang et al. show a similar trend as seen in our POL-2 observations. TADPOL observations demonstrate a well-defined field geometry in MM1/MM2 consistent with MHD simulations of accreting filaments. We obtained a plane-of-sky magnetic field strength of 470$\pm$190\,$\mu$G, 100$\pm$40\,$\mu$G, and 60$\pm$34\,$\mu$G in the central, northern and southern regions of G34, respectively, using the updated Davis-Chandrasekhar-Fermi relation. The estimated value of field strength, combined with column density and velocity dispersion values available in the literature, suggests G34 to be marginally critical with criticality parameter $\rm \lambda$ values 0.8$\pm$0.4, 1.1$\pm$0.8, and 0.9$\pm$0.5 in the central, northern, and southern regions, respectively. The turbulent motions in G34 are sub-Alfv\'{e}nic with Alfv\'{e}nic Mach numbers of 0.34$\pm$0.13, 0.53$\pm$0.30, and 0.49$\pm$0.26 in the three regions. The observed aligned B-fields in G34.43+0.24 are consistent with theoretical models suggesting that B-fields play an important role in guiding the contraction of the cloud driven by gravity., Comment: 16 pages, 10 figures, Accepted for publication in ApJ

In the published article, we presented high-resolution polarimetry data obtained by using JCMT SCUBA-2/POL-2, and compared them with the larger-scale magnetic structure observed by Planck (Planck Collaboration et al. 2020). There was a miscalculation in the analysis of the Planck data for comparison, and the mean position angle of the Planck magnetic field should be corrected from -40° ± 7° to -48° ± 6°. Thus, we replace the descriptions in the published article as follows. In Section 4.2, paragraph 3, the second sentence should read: "The differences between the orientations of IRAS 4A, IRAS 4B, and IRAS 2A are not statistically significant, but they do show significantly different orientations from those of the global B-field observed by Planck (-48° ± 6°; Section 4.1)." In Section 4.1, paragraph 3, the second line should read: "The Planck B-field orientation shows a smoothly and slowly varying field distribution with a position angle of -48° ± 6° in our observed NGC 1333 area." Accordingly, we replace Figures 4, 5, 9, 10, and 17 to reflect the correct Planck data. As described above, this error of modest magnitude is related only to our derivation of the Planck polarization angle, and the JCMT observation results are unaffected. Therefore, all conclusions drawn in the published article are unchanged even after the above correction is applied. The 1 pc scale magnetic field observed by Planck shows a smooth distribution, and the interstellar magnetic field in molecular clouds increases the complexity significantly on the scale of less than 1 pc.

We report the detection of four new hot corino sources, G211.47-19.27S, G208.68-19.20N1, G210.49-19.79W and G192.12-11.10 from a survey study of Planck Galactic Cold Clumps in the Orion Molecular Cloud Complex with the Atacama Compact Array (ACA). Three sources had been identified as low mass Class 0 protostars in the Herschel Orion Protostar Survey (HOPS). One source in the lambda Orionis region is firstly reported as a protostellar core. We have observed abundant complex organic molecules (COMs), primarily methanol but also other oxygen-bearing COMs (in G211.47-19.27S and G208.68-19.20N1) and the molecule of prebiotic interest NH2CHO (in G211.47-19.27S), signifying the presence of hot corinos. While our spatial resolution is not sufficient for resolving most of the molecular emission structure, the large linewidth and high rotational temperature of COMs suggest that they likely reside in the hotter and innermost region immediately surrounding the protostar. In G211.47-19.27S, the D/H ratio of methanol ([CH2DOH]/[CH3OH]) and the 12C/13C ratio of methanol ([CH3OH]/[13CH3OH]) are comparable to those of other hot corinos. Hydrocarbons and long carbon-chain molecules such as c-C3H2 and HCCCN are also detected in the four sources, likely tracing the outer and cooler molecular envelopes., 37 pages, 51 figures, to be published in ApJ

LDN 1157, is one of the several clouds situated in the cloud complex, LDN 1147/1158, represents a coma-shaped morphology with a well-collimated bipolar outflow emanating from a Class 0 protostar, LDN 1157-mm. The main goals of this work are (a) to map the inter-cloud magnetic field (ICMF) geometry of the region surrounding LDN 1157 to investigate its relationship with the cloud morphology, with the outflow direction and with the core magnetic field (CMF) geometry inferred from the mm- and sub-mm polarization results from the literature, and (b) to investigate the kinematic structure of the cloud. We carried out R-band polarization observations of the stars projected on the cloud to map the pc-scale magnetic field geometry and made spectroscopic observations of the entire cloud in 12CO, C18O and N2H+ (J=1-0) lines to investigate its kinematic structure. We obtained a distance of 340$\pm$3 pc to the LDN 1147/1158, complex based on the Gaia DR2 parallaxes and proper motion values of the three YSOs associated with the complex. A single filament of $\sim1.2$ pc in length and $\sim0.09$ pc in width is found to run all along the coma-shaped cloud. Based on the relationships between the ICMF, CMF, filament orientations, outflow direction, and the presence of an hour-glass morphology of the magnetic field, it is likely that the magnetic field had played an important role in the star formation process in LDN 1157. Combining the proper motions of the YSOs and the radial velocity of LDN 1147/1158 and another complex LDN 1172/1174 which is situated $\sim2$\dgr~east of it, we found that both the complexes are moving collectively toward the Galactic plane. The filamentary morphology of the east-west segment of LDN 1157 may have formed as a result of mass lost by ablation due to the interaction of the moving cloud with the ambient interstellar medium., Comment: 20 pages, Accepted in Astronomy & Astrophysics, Abstract has been shortened due to word limit in arxiv

This paper presents our observational attempts to precisely measure the central mass of a proto-brown dwarf candidate, L328-IRS, in order to investigate whether L328-IRS is in the substellar mass regime. Observations were made for the central region of L328-IRS with the dust continuum and CO isotopologue line emission at ALMA band 6, discovering the detailed outflow activities and a deconvolved disk structure of a size of $\sim$87 AU $\times$ 37 AU. We investigated the rotational velocities as a function of the disk radius, finding that its motions between 130 AU and 60 AU are partially fitted with a Keplerian orbit by a stellar object of $\sim0.30 ~\rm\,M_\odot$, while the motions within 60 AU do not follow any Keplerian orbit at all. This makes it difficult to lead a reliable estimation of the mass of L328-IRS. Nonetheless, our ALMA observations were useful enough to well constrain the inclination angle of the outflow cavity of L328-IRS as $\sim 66^{\circ}$, enabling us to better determine the mass accretion rate of $\sim 8.9\times 10^{-7} \rm\,M_\odot~yr^{-1}$. From assumptions that the internal luminosity of L328-IRS is mostly due to this mass accretion process in the disk, or that L328-IRS has mostly accumulated the mass through this constant accretion rate during its outflow activity, its mass was estimated to be $\sim 0.012 - 0.023\rm\,M_\odot$, suggesting L328-IRS to be a substellar object. However, we leave our identification of L328-IRS as a proto-brown dwarf to be tentative because of various uncertainties especially regarding the mass accretion rate., Accepted in ApJ, 24 pages, 12 figures

Magnetic field is one of the key agents that play a crucial role in shaping molecular clouds and regulating star formation, yet the complete information on the magnetic field is not well constrained due to the limitations in observations. We study the magnetic field in the massive infrared dark cloud G035.39-00.33 from dust continuum polarization observations at 850 $\micron$ with SCUBA-2/POL-2 at JCMT. The magnetic field tends to be perpendicular to the densest part of the main filament (F$_{M}$), whereas it has a less defined relative orientation in the rest of the structure, where it tends to be parallel to some diffuse regions. A mean plane-of-the-sky magnetic field strength of $\sim$50 $\mu$G for F$_{M}$ is obtained using Davis-Chandrasekhar-Fermi method. Based on $^{13}$CO (1-0) line observations, we suggest a formation scenario of F$_{M}$ due to large-scale ($\sim$10 pc) cloud-cloud collision. Using additional NH$_3$ line data, we estimate that F$_{M}$ will be gravitationally unstable if it is only supported by thermal pressure and turbulence. The northern part of F$_{M}$, however, can be stabilized by a modest additional support from the local magnetic field. The middle and southern parts of F$_{M}$ are likely unstable even if the magnetic field support is taken into account. We claim that the clumps in F$_{M}$ may be supported by turbulence and magnetic fields against gravitational collapse. Finally, we identified for the first time a massive ($\sim$200 M$_{\sun}$), collapsing starless clump candidate, "c8", in G035.39-00.33. The magnetic field surrounding "c8" is likely pinched, hinting at an accretion flow along the filament., Comment: Published on ApJ, 27 pages

著者人数: 122名 (所属. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS): 權, 靜美; 中西, 裕之; 中川, 貴雄）, Accepted: 2018-03-26, 資料番号: SA1170332000

We present the results of a systematic search for molecular outflows in 68 Very Low Luminosity Objects (VeLLOs) from single-dish observations in CO isotopologues which find 16 VeLLOs showing clear outflow signatures in the CO maps. With additional three VeLLOs from the literature, we analyzed the outflow properties for 19 VeLLOs, identifying 15 VeLLOs as proto-Brown Dwarf (BD) candidates and four VeLLOs as likely faint protostar candidates. The proto-BD candidates are found to have a mass accretion rate ($\sim 10^{-8} - 10^{-7}$ $\rm M_{\odot}$ yr$^{-1}$) lower than that of the protostar candidates ($\gtrsim 10^{-6}$ $\rm M_{\odot}$ yr$^{-1}$). Their accretion luminosities are similar to or smaller than their internal luminosities, implying that many proto-BD candidates might have had either small accretion activity in a quiescent manner throughout their lifetime, or be currently exhibiting a relatively higher (or episodic) mass accretion than the past. There are strong trends that outflows of many proto-BDs are less active if they are fainter or have less massive envelopes. The outflow forces and internal luminosities for more than half of the proto-BD candidates seem to follow an evolutionary track of a protostar with its initial envelope mass of $\sim$0.08 $\rm M_{\odot}$, indicating that some BDs may form in less massive dense cores in a way similar to normal stars. But, because there also exists a significant fraction (about 40%) of proto-BDs with much weaker outflow force than expected by the relations for protostars, we should not rule out the possibility of other formation mechanism for the BDs., Comment: 32 pages, 9 Figures, 5 Tables, Accepted for publication in ApJS

著者人数: 124名（所属. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS): 權, 靜美), Accepted: 2018-05-10, 資料番号: SA1180101000

Most protostars have luminosities that are fainter than expected from steady accretion over the protostellar lifetime. The solution to this problem may lie in episodic mass accretion -- prolonged periods of very low accretion punctuated by short bursts of rapid accretion. However, the timescale and amplitude for variability at the protostellar phase is almost entirely unconstrained. In "A JCMT/SCUBA-2 Transient Survey of Protostars in Nearby Star Forming Regions", we are monitoring monthly with SCUBA-2 the sub-mm emission in eight fields within nearby (, ApJ, accepted

The dependence of polarization fraction $p$ on total intensity $I$ in polarized submillimeter emission measurements is typically parameterized as $p\propto I^{-\alpha}$ $(\alpha \leq 1)$, and used to infer dust grain alignment efficiency in star-forming regions, with an index $\alpha=1$ indicating near-total lack of alignment of grains with the magnetic field. In this work we demonstrate that the non-Gaussian noise characteristics of polarization fraction may produce apparent measurements of $\alpha \sim 1$ even in data with significant signal-to-noise in Stokes $Q$, $U$ and $I$ emission, and so with robust measurements of polarization angle. We present a simple model demonstrating this behavior, and propose a criterion by which well-characterized measurements of polarization fraction may be identified. We demonstrate that where our model is applicable, $\alpha$ can be recovered by fitting the $p-I$ relationship with the mean of the Rice distribution, without statistical debiasing of polarization fraction. We apply our model to JCMT BISTRO Survey POL-2 850$\mu$m observations of three clumps in the Ophiuchus Molecular Cloud, finding that in the externally-illuminated Oph A region, $\alpha\approx 0.34$, while in the more isolated Oph B and C, despite their differing star formation histories, $\alpha \sim 0.6-0.7$. Our results thus suggest that dust grain alignment in dense gas is more strongly influenced by incident interstellar radiation field than by star formation history. We further find that grains may remain aligned with the magnetic field at significantly higher gas densities than has previously been believed, thus allowing investigation of magnetic field properties within star-forming clumps and cores., Comment: 21 pages, 8 figures, 3 tables, accepted for publication in ApJ

We present results of our study on eight dense cores, previously classified as starless, using infrared (3-160 {\micron}) imaging observations with \textit{AKARI} telescope and molecular line (HCN and N$_2$H$^+$) mapping observations with \textit{KVN} telescope. Combining our results with the archival IR to mm continuum data, we examined the starless nature of these eight cores. Two of the eight cores are found to harbor faint protostars having luminosity of $\sim0.3-4.4$ L$_{\odot}$. The other six cores are found to remain as starless and probably are in a dynamically transitional state. The temperature maps produced using multi-wavelength images show an enhancement of about 3-6 K towards the outer boundary of these cores, suggesting that they are most likely being heated externally by nearby stars and/or interstellar radiation fields. Large virial parameters and an over-dominance of red asymmetric line profiles over the cores may indicate that the cores are set into either an expansion or an oscillatory motion, probably due to the external heating. Most of the starless cores show coreshine effect due to the scattering of light by the micron-size dust grains. This may imply that the age of the cores is of the order of $\sim10^{5}$ years, being consistent with the timescale required for the cores to evolve into an oscillatory stage due to the external perturbation. Our observational results support the idea that the external feedback from nearby stars and/or interstellar radiation fields may play an important role in the dynamical evolution of the cores., Comment: 48 pages, 8 figures,accepted for publication in ApJ

We present the R-band polarimetric results towards two nebulae L1415 and L1389 containing low luminosity stars. Aim of this study is to understand the role played by magnetic fields in formation of low luminosity objects. Linear polarization arise due to dichroism of the background starlight projected on the cloud providing the plane-of-the sky magnetic field orientation. The offsets between mean magnetic field directions obtained towards L1415 and L1389 and the projected outflow axes are found to be 35$^{\circ}$ and 12$^{\circ}$, respectively. The offset between cloud minor axes and mean envelope magnetic field direction in L1415 and L1389 are 50$^{\circ}$ and 87$^{\circ}$, respectively. To estimate the magnetic field strength by using the updated Chandrasekhar-Fermi relation, we obtained the $^{12}$CO(J=1-0) line velocity dispersion value towards L1415 cloud using the TRAO single dish observations. The values of B$_{pos}$ in L1415 and L1389 are found to be 28$~\mu$G and 149$~\mu$G using CF technique and 23$~\mu$G and 140$~\mu$G using structure function analysis, respectively. The values of B$_{pos}$ in these clouds are found to be consistent using both the techniques. By combining the present results with those obtained from our previous study of magnetic fields in cores with VeLLOs, we attempt to improve the sample of cores with low luminosity protostars and bridge the gap between the understanding of importance of magnetic fields in cores with VeLLOs and low luminosity protostars. The Results of this work and that of our previous work show that the outflow directions are aligned with envelope magnetic fields of the clouds., Comment: 18 pages, 11 figures, accepted for publication in MNRAS

In this paper we examined theassociation of InfraRed Dark Cloud (IRDC) cores with YSOs and the geometric properties of the IRDC cores. For this studya total of 13,650 IRDC cores were collected mainly from the catalogs of the IRDC cores published from other studies andpartially from our catalog of IRDC cores containing new 789 IRDC core candidates. The YSO candidates were searched for usingthe GLIMPSE, MSX, and IRAS point sources by the shape of their SED or using activity of water or methanol maser. The associationof the IRDC cores with these YSOs was checked by their line- of-sight coincidence within the dimension of the IRDC core.This work found that a total of 4,110 IRDC cores have YSO candidates while 9,540 IRDC cores have no indication of the existenceof YSOs. Considering the 12,200 IRDC cores within the GLIMPSE survey region for which the YSO candidates were determinedwith better sensitivity, we found that 4,098 IRDC cores (34%) have at least one YSO candidate and 1,072 cores among themseem to have embedded YSOs, while the rest 8,102 (66%) have no YSO candidate. Therefore, the ratio of [N(IRDC core with protostars)]/[N(IRDCcore without YSO)] for 12,200 IRDC cores is about 0.13. Taking into account this ratio and typical lifetime of high-massembedded YSOs, we suggest that the IRDC cores would spend about 104 ~ 105 years to form high-mass stars.However, we should note that the GLIMPSE point sources have a minimum detectable luminosity of about 1.2 Lq at a typical IRDC core"s distanceof ~4 kpc. Therefore, the ratio given here should be a lower limit and the estimated lifetime of starless IRDC cores canbe an upper limit. The physical parameters of the IRDC cores somewhat vary depending on how many YSO candidates the IRDCcores contain. The IRDC cores with more YSOs tend to be larger, more elongated, and have better darkness contrast than theIRDC cores with fewer or no YSOs.

[Abridged] We carried out optical polarimetry of five dense cores, (IRAM 04191, L1521F, L328, L673-7, and L1014) which are found to harbour VeLLO. This study was conducted mainly to understand the role played by the magnetic field in the formation of very low and substellar mass range objects using optical polarisation. The angular offsets between the envelope magnetic field direction (inferred from optical polarisation measurements) and the outflow position angles from the VeLLOs in IRAM 04191, L1521F, L328, L673-7, and L1014 are found to be 84$^\circ$, 53$^\circ$, 24$^\circ$, 08$^\circ$, and 15$^\circ$, respectively. The mean value of the offsets for all the five clouds is $\sim37^\circ$. If we exclude IRAM 04191, the mean value reduces to become $\sim25^\circ$. In IRAM 04191, the offset between the projected envelope and the inner magnetic field (inferred from the submillimetre data from SCUPOL) is found to be $\sim68^\circ$. The inner magnetic field, however, is found to be nearly aligned with the projected position angles of the minor axis, the rotation axis of the cloud, and the outflow from the IRAM 04191-IRS. We discuss a possible explanation for the nearly perpendicular orientation between the envelope and core scale magnetic fields in IRAM04191. The angular offset between the envelope magnetic field direction and the minor axis of IRAM 04191, L1521F, L673-7, and L1014 are 82$^\circ$, 60$^\circ$, 47$^\circ$, and 55$^\circ$, respectively. The mean value of the offsets between the envelope magnetic field and the minor axis position angles for the four cores is found to be $\sim60^\circ$. The results obtained from our study on the limited sample of five cores with VeLLOs show that the outflows in three of them tend to nearly align with the envelope magnetic field., Comment: 18 pages, 18 figures, 5 tables, due to length limitation, the abstract appearing here is abridged

This paper presents the results of millimeter to sub-millimeter observations of CO, HCN, N2H+, and HCO+ lines in the dense molecular cloud L328, which harbors L328-IRS, a Very Low Luminosity Object (VeLLO). Our analysis of the line width finds that 13CO and N2H+ lines are broadened right over the smallest sub-core S2 where L328-IRS is located, while they are significantly narrower in other regions of L328. Thus, L328-IRS has a direct association with the sub-core. CO observations show a bipolar outflow from this VeLLO with an extent of ~0.08 pc. The outflow momentum flux and efficiency are much less than those of low-mass protostars. The most likely mass accretion rate (~3.6 × 10–7 M ☉ yr–1) inferred from the analysis of the CO outflow is an order of magnitude smaller than the canonical value for a protostar. If the main accretion lasts during the typical Class 0 period of a protostar, L328-IRS will accrete the mass of a brown dwarf, but not that of a star. Given that its envelope mass is small (~0.09 M ☉) and 100% star formation rate is unlikely, we suggest that L328-IRS is likely a proto-brown dwarf. Inward motions are found in global scale in the L328 cloud and its sub-cores with a typical infall speed found in starless cores. L328 is found to be fairly well isolated from other nearby clouds and seems to be forming three sub-cores simultaneously through a gravitational fragmentation process. Altogether, these all leave L328-IRS as the best example supporting the idea that a brown dwarf forms like a normal star.