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61. New Taurus members from stellar to planetary masses
ID:
ivo://CDS.VizieR/J/AJ/158/54
Title:
New Taurus members from stellar to planetary masses
Short Name:
J/AJ/158/54
Date:
06 Dec 2021 11:31:43
Publisher:
CDS
Description:
We present a large sample of new members of the Taurus star-forming region that extend from stellar to planetary masses. To identify candidate members at substellar masses, we have used color-magnitude diagrams and proper motions measured with several wide-field optical and infrared (IR) surveys. At stellar masses, we have considered the candidate members that were found in a recent analysis of high-precision astrometry from the Gaia mission. Using new and archival spectra, we have measured spectral types and assessed membership for these 161 candidates, 79 of which are classified as new members. Our updated census of Taurus now contains 519 known members. According to Gaia data, this census should be nearly complete for spectral types earlier than M6-M7 at A_J_<1. For a large field encompassing ~72% of the known members, the census should be complete for K<15.7 at A_J_<1.5, which corresponds to ~5-13 M_Jup_ for ages of 1-10 Myr based on theoretical evolutionary models. Our survey has doubled the number of known members at >=M9 and has uncovered the faintest known member in M_K_, which should have a mass of ~3-10 M_Jup_ for ages of 1-10 Myr. We have used mid-IR photometry from the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer to determine whether the new members exhibit excess emission that would indicate the presence of circumstellar disks. The updated disk fraction for Taurus is ~0.7 at =<M3.5 and ~0.4 at >M3.5.
62. N in Galactic high-mass star-forming cores
ID:
ivo://CDS.VizieR/J/MNRAS/478/3693
Title:
N in Galactic high-mass star-forming cores
Short Name:
J/MNRAS/478/3693
Date:
10 Dec 2021 00:14:43
Publisher:
CDS
Description:
The fractionation of nitrogen (N) in star-forming regions is a poorly understood process. To put more stringent observational constraints on the N-fractionation, we have observed with the IRAM-30-m telescope a large sample of 66 cores in massive star-forming regions. We targeted the (1-0) rotational transition of HN^13^C, HC^15^N, H^13^CN and HC^15^N, and derived the ^14^N/^15^N ratio for both HCN and HNC. We have completed this sample with that already observed by Colzi et al., and thus analysed a total sample of 87 sources. The ^14^N/^15^N ratios are distributed around the Proto-Solar Nebula value with a lower limit near the TA value (~272). We have also derived the ^14^N/^15^N ratio as a function of the Galactocentric distance and deduced a linear trend based on unprecedented statistics. The Galactocentric dependences that we have found are consistent, in the slope, with past works but we have found a new local ^14^N/^15^N value of ~400, i.e. closer to the Prosolar Nebula value. A second analysis was done, and a parabolic Galactocentric trend was found. Comparison with Galactic chemical evolution models shows that the slope until 8 kpc is consistent with the linear analysis, while the flattening trend above 8 kpc is well reproduced by the parabolic analysis.
63. NIR polarimetric study in the LMC N159/N160 field
ID:
ivo://CDS.VizieR/J/AJ/153/126
Title:
NIR polarimetric study in the LMC N159/N160 field
Short Name:
J/AJ/153/126
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present near-infrared polarimetric results for the N159/N160 star-forming complex in the Large Magellanic Cloud with SIRPOL, the polarimeter of the Infrared Survey Facility. We separated foreground sources using their visual extinction derived from near-infrared photometric data. The 45 young stellar candidates and 2 high-excitation blobs were matched with our sources, and 12 of them showed high polarization that did not originate from the interstellar dust. We made a polarimetric catalog of 252, 277, and 89 sources at the J, H, and K_s_ bands, respectively. Based on the ratios of the polarization degree between these bands, we verify that the origin of these polarized sources is the dichroic extinction from the interstellar dust aligned by the magnetic field and that the ratios follow a power-law dependence of P_{lambda}_~{lambda}^-0.9^. The linear polarization vectors projected onto the H{alpha} image of the complex turned out to follow the local magnetic field structure. The vector map overlaid on dust and gas emissions shows the close correlation between the magnetic field structure and surrounding interstellar medium. We suggest that the derived magnetic field structure supports the sequential formation scenario of the complex.
64. Optical and IR photometry in the HII region Sh2-242
ID:
ivo://CDS.VizieR/J/AJ/159/153
Title:
Optical and IR photometry in the HII region Sh2-242
Short Name:
J/AJ/159/153
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present here identification and characterization of the young stellar population associated with an active star-forming site Sh2-242. We used our own new optical imaging and spectroscopic observational data, as well as several archival catalogs, e.g., Pan-STARRS-1, Gaia-DR2, Isaac Newton Telescope Photometric H-Alpha Survey (IPHAS), Wide-field InfraRed Camera, 2MASS, and Spitzer. Slit spectroscopic results confirm the classification of the main ionizing source BD+26980 as an early-type star of spectral type B0.5V. The spectrophotometric distance of the star is estimated as 2.08{+/-}0.24kpc, which confirms the source as a member of the cluster. An extinction map covering a large area (diameter ~50') is generated with H and K photometry toward the region. From the map, three distinct locations of peak extinction complexes (A_V_~7-17mag) are identified for the very first time. Using the infrared color excess, a total of 33 Class I and 137 Class II young objects are classified within the region. The IPHAS photometry reveals classification of 36 H{alpha} emitting sources, which might be class II objects. Among 36 H{alpha} emitting sources, 5 are already identified using infrared excess emission. In total, 201 young objects are classified toward S242 from this study. The membership status of the young sources is further windowed with the inclusion of parallax from the Gaia DR2 catalog. Using the optical and infrared color-magnitude diagrams, the young stellar objects are characterized with an average age of ~1Myr and masses in the range 0.1-3.0M_{sun}_.
65. Paramaters for 40 LITTLE THINGS galaxies
ID:
ivo://CDS.VizieR/J/AJ/161/71
Title:
Paramaters for 40 LITTLE THINGS galaxies
Short Name:
J/AJ/161/71
Date:
21 Oct 2021
Publisher:
CDS
Description:
The stellar, gaseous and young stellar disks in the LITTLE THINGS sample of nearby dwarf irregular galaxies are fitted with functions to search for correlations between the parameters. We find that the HI radial profiles are generally flatter in the center and fall faster in the outer regions than the V-band profiles, while young stars are more centrally concentrated, especially if the HI is more centrally flat. This pattern suggests that the HI is turning into molecules in the center, and the molecular clouds are forming stars and FUV. A model that assumes the molecular surface density is proportional to the total gas surface density to a power of 1.5 or 2, in analogy with the Kennicutt-Schmidt relation, reproduces the relationship between the ratio of the visible to the HI scale length and the HI Sersic index. The molecular fraction is estimated as a function of radius for each galaxy by converting the FUV to a molecular surface density using conventional calibrations. The average molecular fraction inside 3RD is 23%{+/-}17%. However, the break in the stellar surface brightness profile has no unified tracer related to star formation.
66. Parameters of protoplanetary disks in 5 SFRs
ID:
ivo://CDS.VizieR/J/ApJ/899/55
Title:
Parameters of protoplanetary disks in 5 SFRs
Short Name:
J/ApJ/899/55
Date:
14 Mar 2022 07:11:43
Publisher:
CDS
Description:
Spatial correlations among protoplanetary disk orientations carry unique information on physics of multiple-star formation processes. We select five nearby star-forming regions that comprise a number of protoplanetary disks with spatially resolved images with ALMA and Hubble Space Telescope, and we search for the mutual alignment of the disk axes. Specifically, we apply the Kuiper test to examine the statistical uniformity of the position angle (PA: the angle of the major axis of the projected disk ellipse measured counterclockwise from the north) distribution. The disks located in the star-forming regions, except the Lupus clouds, do not show any signature of the alignment, supporting the random orientation. Rotational axes of 16 disks with spectroscopic measurement of PA in the LupusIII cloud, a subregion of the Lupus field, however, exhibit a weak and possible departure from the random distribution at a 2{sigma} level, and the inclination angles of the 16 disks are not uniform as well. Furthermore, the mean direction of the disk PAs in the LupusIII cloud is parallel to the direction of its filament structure and approximately perpendicular to the magnetic field direction. We also confirm the robustness of the estimated PAs in the Lupus clouds by comparing the different observations and estimators based on three different methods, including sparse modeling. The absence of the significant alignment of the disk orientation is consistent with the turbulent origin of the disk angular momentum. Further observations are required to confirm/falsify the possible disk alignment in the Lupus III cloud.
67. PGCCs in lambda Orionis complex. II. Cores at 850um
ID:
ivo://CDS.VizieR/J/ApJS/236/51
Title:
PGCCs in lambda Orionis complex. II. Cores at 850um
Short Name:
J/ApJS/236/51
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on the 850{mu}m dust continuum data from SCUBA-2 at James Clerk Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold Clumps (PGCCs) in the {lambda} Orionis cloud to those of PGCCs in the Orion A and B clouds. The Orion A and B clouds are well-known active star-forming regions, while the {lambda} Orionis cloud has a different environment as a consequence of the interaction with a prominent OB association and a giant HII region. PGCCs in the {lambda} Orionis cloud have higher dust temperatures (T_d_=16.13+/-0.15K) and lower values of dust emissivity spectral index ({beta}=1.65+/-0.02) than PGCCs in the Orion A (T_d_=13.79+/-0.21K, {beta}=2.07+/-0.03) and Orion B (T_d_=13.82+/-0.19K, {beta}=1.96+/-0.02) clouds. We find 119 substructures within the 40 detected PGCCs and identify them as cores. Out of a total of 119 cores, 15 cores are discovered in the {lambda} Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds, respectively. The cores in the {lambda} Orionis cloud show much lower mean values of size R=0.08pc, column density N(H_2_)=(9.5+/-1.2)x10^22^cm^-2^, number density n(H_2_)=(2.9+/-0.4)x10^5^cm^-3^, and mass M_core_=1.0+/-0.3M_{sun}_ compared to the cores in the Orion A [R=0.11pc, N(H_2_)=(2.3+/-0.3)x10^23^cm^-2^, n(H_2_)=(3.8+/-0.5)x10^5^cm^-3^, and M_core_=2.4+/-0.3M_{sun}_] and Orion B [R=0.16pc, N(H_2_)=(3.8+/-0.4)x10^23^cm^-2^, n(H_2_)=(15.6+/-1.8)x10^5^cm^-3^, and M_core_=2.7+/-0.3M_{sun}_] clouds. These core properties in the {lambda} Orionis cloud can be attributed to the photodissociation and external heating by the nearby H II region, which may prevent the PGCCs from forming gravitationally bound structures and eventually disperse them. These results support the idea of negative stellar feedback on core formation.
68. Photometry of 38708 stars in W3 complex with HST
ID:
ivo://CDS.VizieR/J/AJ/161/138
Title:
Photometry of 38708 stars in W3 complex with HST
Short Name:
J/AJ/161/138
Date:
11 Mar 2022
Publisher:
CDS
Description:
We have used archival infrared images obtained with the Wide Field Camera 3 on board the Hubble Space Telescope to constrain the initial mass function of low-mass stars and brown dwarfs in the W3 star-forming region. The images cover 438arcmin^2^, which encompasses the entire complex, and were taken in the filters F110W, F139M, and F160W. We have estimated extinctions for individual sources in these data from their colors and have dereddened their photometry accordingly. By comparing an area of the images that contains the richest concentration of previously identified W3 members to an area that has few members and is dominated by background stars, we have estimated the luminosity function for members of W3 with masses of 0.03-0.4M{sun}. That luminosity function closely resembles data in typical nearby star-forming regions that have much smaller stellar populations than W3 ( ~500 versus several thousand objects). Thus, we do not find evidence of significant variations in the initial mass function of low-mass stars and brown dwarfs with star-forming conditions, which is consistent with recent studies of other distant massive star-forming regions.
69. Physical properties of SFRs in NGC 3395/NGC 3396
ID:
ivo://CDS.VizieR/J/AJ/159/17
Title:
Physical properties of SFRs in NGC 3395/NGC 3396
Short Name:
J/AJ/159/17
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report long-slit spectroscopy of the early major merger galaxies NGC 3395/NGC 3396. The spectra are consistent with those for star-forming galaxies, but there is some indication of LINER-like active galactic nucleus activity in the center of NGC 3396. The total star formation rate in the regions observed is 2.83 M_{sun}_/yr, consistent with estimates for the entire galaxies. The highest abundances are in the centers of the galaxies, with the abundances decreasing with distance. There is a correlation between high abundance and high ionization parameter, both of which can be attributed to the presence of massive stars. Modeling with SB 99 indicates the star-forming regions are younger than 10 Myr. There are 1000-2000 WNL stars in the system, along with several thousand O stars, consistent with the ages of the star-forming regions. The highest electron densities are found in young regions with high star formation rates. The electron temperatures are higher than results for non-interacting galaxies, which is probably due to shock waves produced by the galaxy-galaxy interaction, the outflow of gas from massive stars, and/or collisions between gas clouds in the galaxies. There is star formation in the bridge of material between the galaxies. These regions are among the youngest in the system and have low abundances, suggesting the gas was pulled from the outer parts of the galaxies. X-ray point sources, probably high-mass X-ray binaries, are associated with several star-forming regions.
70. Planck Cold Clumps in the lambda Orionis complex. III.
ID:
ivo://CDS.VizieR/J/ApJS/254/14
Title:
Planck Cold Clumps in the lambda Orionis complex. III.
Short Name:
J/ApJS/254/14
Date:
17 Jan 2022 00:15:36
Publisher:
CDS
Description:
Massive stars have a strong impact on their local environments. However, how stellar feedback regulates star formation is still under debate. In this context, we studied the chemical properties of 80 dense cores in the Orion molecular cloud complex composed of the Orion A (39 cores), B (26 cores), and {lambda} Orionis (15 cores) clouds using multiple molecular line data taken with the Korean Very Long Baseline Interferometry Network 21m telescopes. The {lambda} Orionis cloud has an HII bubble surrounding the O-type star {lambda} Ori, and hence it is exposed to the ultraviolet (UV) radiation field of the massive star. The abundances of C_2_H and HCN, which are sensitive to UV radiation, appear to be higher in the cores in the {lambda} Orionis cloud than in those in the Orion A and B clouds, while the HDCO to H_2_CO abundance ratios show the opposite trend, indicating warmer conditions in the {lambda} Orionis cloud. The detection rates of dense gas tracers such as the N_2_H^+^, HCO^+^, and H^13^CO^+^ lines are also lower in the {lambda} Orionis cloud. These chemical properties imply that the cores in the {lambda} Orionis cloud are heated by UV photons from {lambda} Ori. Furthermore, the cores in the {lambda} Orionis cloud do not show any statistically significant excess in the infall signature of HCO^+^ (1-0), unlike those in the Orion A and B clouds. Our results support the idea that feedback from massive stars impacts star formation in a negative way by heating and evaporating dense materials, as in the {lambda} Orionis cloud.

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