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71. Post-AGB evolution
ID:
ivo://CDS.VizieR/J/ApJS/92/125
Title:
Post-AGB evolution
Short Name:
J/ApJS/92/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we present the results for the post-AGB phases of stellar evolutionary sequences, complete from the main-sequence phase, through the AGB phase, and on into the planetary nebula and white dwarf regimes. Mass loss has been included using an empirical formalism derived from observed mass-loss rates of planetary nebula nuclei available in the literature and from radiation-pressure-driven stellar wind theory. Models are calculated for initial masses 0.89, 0.95, 1.0, 1.5, 2.0, 2.5, 3.5, and 5.0M_{sun}_, and metallicities 0.016, 0.008, 0.004, and 0.001. These abundance and mass values were chosen to allow comparison with Galactic, and Magellanic Cloud planetary nebulae and their nuclei. The post-AGB evolutionary sequences fall into two distinct groups depending on when the planetary nebula nuclei leave the AGB: one group where helium-shell burning is dominant, and the other group where hydrogen-shell burning is dominant. Of the 27 computed sequences: 17 are hydrogen-burners, and 10 are helium-burners. In only five cases was any effort made to control the phase of departure from the AGB. Lower mass models are more likely to leave the AGB burning helium, as the preceding AGB evolution has a mass-loss rate which is greatest immediately prior to a helium-shell flash. The calculations are compared with the large observational database that has developed over recent years for the Large Magellanic Cloud. These calculations will be useful for determining the planetary nebula luminosity function, and for the study of the ultraviolet excess observed in elliptical galaxies.
72. Properties of clumps in the NAN complex
ID:
ivo://CDS.VizieR/J/AJ/147/46
Title:
Properties of clumps in the NAN complex
Short Name:
J/AJ/147/46
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present observations of a 4.25deg^2^ area toward the North American and Pelican Nebulae in the J=1-0 transitions of ^12^CO, ^13^CO, and C^18^O. Three molecules show different emission areas with their own distinct structures. These different density tracers reveal several dense clouds with a surface density of over 500M_{sun}_pc^-2^ and a mean H_2_ column density of 5.8, 3.4, and 11.9x10^21^/cm2 for ^12^CO, ^13^CO, and C^18^O, respectively. We obtain a total mass of 5.4x10^4^M_{sun}_(^12^CO), 2.0x10^4^M_{sun}_(^13^CO), and 6.1x10^3^M_{sun}_(C^18^O) in the complex. The distribution of excitation temperature shows two phases of gas: cold gas (~10K) spreads across the whole cloud; warm gas (>20K) outlines the edge of the cloud heated by the W80 HII region. The kinetic structure of the cloud indicates an expanding shell surrounding the ionized gas produced by the HII region. There are six discernible regions in the cloud: the Gulf of Mexico, Caribbean Islands and Sea, and Pelican's Beak, Hat, and Neck. The areas of ^13^CO emission range within 2-10pc^2^ with mass of (1-5)x10^3^M_{sun}_ and line width of a few km/s. The different line properties and signs of star-forming activity indicate they are in different evolutionary stages. Four filamentary structures with complicated velocity features are detected along the dark lane in LDN 935. Furthermore, a total of 611 molecular clumps within the ^13^CO tracing cloud are identified using the ClumpFind algorithm. The properties of the clumps suggest that most of the clumps are gravitationally bound and at an early stage of evolution with cold and dense molecular gas.
73. ROSAT survey of the Orion nebula region
ID:
ivo://CDS.VizieR/J/ApJ/445/280
Title:
ROSAT survey of the Orion nebula region
Short Name:
J/ApJ/445/280
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from three deep ROSAT high-resolution imager observations of the Orion Nebula star-forming region. The X-ray images contain over 1500 catalogued stars in a roughly 0.8deg^2^ region centered on the Trapezium. In all, 389 distinct X-ray sources have been detected, at least two-thirds of which are associated with a single proper-motion cluster member. X-ray emission is detected from stars of all spectral types, from the massive O- and B-type components of the Trapezium to the coolest, low-mass pre-main-sequence (PMS) stars. In this paper, we focus primarily on X-ray emission from the late-type PMS stars. Of the ~100 late-type cluster members with measured spectral types, approximately three-fourths have been detected; we have derived X-ray luminosity upper limits for the remaining stars. We found coronal X-ray emission turns on around spectral type F6, with the upper envelope of activity increasing with decreasing effective temperature.
74. Rosette Nebula and Maddalena Cloud structures
ID:
ivo://CDS.VizieR/J/ApJ/428/693
Title:
Rosette Nebula and Maddalena Cloud structures
Short Name:
J/ApJ/428/693
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe an automatic, objective routine for analyzing the clumpy structure in a spectral line position-position-velocity data cube. The algorithm works by first contouring the data at a multiple of the rms noise of the observations, then searches for peaks of emission which locate the clumps, and then follows them down to lower intensities. No a priori clump profile is assumed. By creating simulated data, we test the performance of the algorithm and show that a contour map most accurately depicts internal structure at a contouring interval equal to twice the rms noise of the map. Blending of clump emission leads to small errors in mass and size determinations and in severe cases can result in a number of clumps being misidentified as a single unit, flattening the measured clump mass spectrum. The algorithm is applied to two real data sets as an example of its use. The Rosette molecular cloud is a "typical" star-forming cloud, but in the Maddalena molecular cloud high-mass star formation is completely absent. Comparison of the two clump lists generated by the algorithm show that on a one-to-one basis the clumps in the star-forming cloud have higher peak temperatures, higher average densities, and are more gravitationally bound than in the non star-forming cloud. Collective properties of the clumps, such as temperature-size-line-width-mass relations appear very similar, however. Contrary to the initial results reported in a previous paper (Williams & Blitz, 1993ApJ...405L..75W), we find that the current, more thoroughly tested analysis finds no significant difference in the clump mass spectrum of the two clouds.
75. Rosette Nebula globules
ID:
ivo://CDS.VizieR/J/A+A/605/A82
Title:
Rosette Nebula globules
Short Name:
J/A+A/605/A82
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Rosette nebula is an HII region ionized mainly by the stellar cluster NGC 2244. Elephant trunks, globules, and globulettes are seen at the interface where the HII region and the surrounding molecular shell meet. We have observed a field in the northwestern part of the Rosette nebula where we study the small globules protruding from the shell. Our aim is to measure their properties and study their star-formation history in continuation of our earlier study of the features of the region. We imaged the region in broadband near-infrared (NIR) JsHKs filters and narrowband H_2_ 1-0 S(1), P{beta}, and continuum filters using the SOFI camera at the ESO/NTT. The imaging was used to study the stellar population and surface brightness, create visual extinction maps, and locate star formation. Mid-infrared (MIR) Spitzer IRAC and WISE and optical NOT images were used to further study the star formation and the structure of the globules. The NIR and MIR observations indicate an outflow, which is confirmed with CO observations made with APEX.
76. Rotation in molecular clouds
ID:
ivo://CDS.VizieR/J/A+AS/134/241
Title:
Rotation in molecular clouds
Short Name:
J/A+AS/134/241
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have investigated a broad range of evidence concerning rotation in molecular clouds. As a consequence, we show that trends in specific angular momentum J/M and angular velocity {Omega} are inconsistent with certain models of isothermal, non-magnetic cloud rotation. Similarly, models of rotation which invoke turbulent vorticity may have only limited applicability to clumps and condensations. There is evidence to favour an important role for rotation in maintaining the stability of disks, larger cloud structures, and perhaps a large fraction of intermediate sized clouds, whilst rotation may also be implicated in maintaining observed departures from cloud sphericity.
77. SABOCA imaging of G304.74+01.32
ID:
ivo://CDS.VizieR/J/A+A/609/A123
Title:
SABOCA imaging of G304.74+01.32
Short Name:
J/A+A/609/A123
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim to determine the occurrence of fragmentation into cores in the clumps of the filamentary IRDC G304.74+01.32. We also aim to determine the basic physical characteristics of the clumps and cores in G304.74. We mapped the G304.74 filament at 350 micron using the SABOCA bolometer. The new SABOCA data have a factor of 2.2 times higher resolution than our previous LABOCA 870 micron map of the cloud (9" versus 19.86"). We also employed the Herschel far-IR and submillimetre, and WISE IR imaging data available for G304.74. The WISE data allowed us to trace the IR emission of the YSOs associated with the cloud. The SABOCA 350 micron data show that G304.74 is composed of a dense filamentary structure with a mean width of only 0.18+/-0.05pc. The percentage of LABOCA clumps that are found to be fragmented into SABOCA cores is 36%+/-16%, but the irregular morphology of some of the cores suggests that this multiplicity fraction could be higher. The WISE data suggest that 65%+/-18% of the SABOCA cores host YSOs. The mean dust temperature of the clumps, derived by comparing the Herschel 250, 350, and 500 micron flux densities, was found to be 15.0+/-0.8K. The mean mass, beam-averaged H_2_ column density, and H_2_ number density of the LABOCA clumps are estimated to be 55+/-10M_{sun}_, (2.0+/-0.2)x10^22^cm^-2^, and (3.1+/-0.2)x10^4^cm^-3^. The corresponding values for the SABOCA cores are 29+/-3M_{sun}_, (2.9+/-0.3)x10^22^cm^-2^, and (7.9+/-1.2)x10^4^cm^-3^. The G304.74 filament is estimated to be thermally supercritical by a factor of >~3.5 on the scale probed by LABOCA, and by a factor of >~1.5 for the SABOCA filament. Our data strongly suggest that the IRDC G304.74 has undergone hierarchical fragmentation. On the scale where the clumps have fragmented into cores, the process can be explained in terms of gravitational Jeans instability. Besides the filament being fragmented, the finding of embedded YSOs in G304.74 indicates its thermally supercritical state, although the potential non-thermal (turbulent) motions can render the cloud a virial equilibrium system on scale traced by LABOCA. The IRDC G304.74 has a seahorse-like morphology in the Herschel images, and the filament appears to be attached by elongated, perpendicular striations. This is potentially evidence that G304.74 is still accreting mass from the surrounding medium, and the accretion process can contribute to the dynamical evolution of the main filament. One of the clumps in G304.74, IRAS 13039-6108, is already known to be associated with high-mass star formation, but the remaining clumps and cores in this filament might preferentially form low and intermediate-mass stars owing to their mass reservoirs and sizes. Besides the presence of perpendicularly oriented, dusty striations and potential embedded intermediate-mass YSOs, G304.74 is a relatively nearby (d~2.5kpc) IRDC, which makes it a useful target for future star formation studies. Owing to its observed morphology, we propose that G304.74 could be nicknamed the Seahorse Nebula. Description: The SABOCA 350 micron and LABOCA 870 micron dust continuum maps of G304.74+01.32. The data were reduced using the CRUSH-2 software
78. SDC13 infrared dark clouds spectra
ID:
ivo://CDS.VizieR/J/A+A/561/A83
Title:
SDC13 infrared dark clouds spectra
Short Name:
J/A+A/561/A83
Date:
21 Oct 2021
Publisher:
CDS
Description:
Formation of stars is now believed to be tightly linked to the dynamical evolution of interstellar filaments in which they form. In this paper we analyze the density structure and kinematics of a small network of infrared dark filaments, SDC13, observed in both dust continuum and molecular line emission with the IRAM 30m telescope. These observations reveal the presence of 18 compact sources amongst which the two most massive, MM1 and MM2, are located at the intersection point of the parsec-long filaments. The dense gas velocity and velocity dispersion observed along these filaments show smooth, strongly correlated, gradients. We discuss the origin of the SDC13 velocity field in the context of filament longitudinal collapse. We show that the collapse timescale of the SDC13 filaments (from 1Myr to 4Myr depending on the model parameters) is consistent with the presence of Class I sources in them, and argue that, on top of bringing more material to the centre of the system, collapse could generate additional kinematic support against local fragmentation, helping the formation of starless super-Jeans cores. SDC13 is composed of three Spitzer Dark Clouds from the Peretto & Fuller (2009, cat J/A+A/505/405) catalogue (SDC13.174-0.07, SDC13.158-0.073, SDC13.194-0.073).
79. SMC and Bridge extended catalog
ID:
ivo://CDS.VizieR/J/ApJS/101/41
Title:
SMC and Bridge extended catalog
Short Name:
J/ApJS/101/41
Date:
21 Oct 2021
Publisher:
CDS
Description:
A survey of extended objects in the Magellanic System was carried out on the ESO/SERC R and J Sky Survey Atlases. The present work is dedicated to the Small Magellanic Cloud and to the inter-Magellanic Cloud region ("Bridge") totaling 1188 objects, of which 554 are classified as star clusters, 343 are emissionless associations, and 291 are related to emission nebulae. The survey includes cross-identifications among catalogs, and we present 284 new objects. We provide accurate positions, classification, homogeneous sizes, and position angles, as well as information on cluster pairs and hierarchical relation for superimposed objects. Two clumps of extended objects in the Bridge and one at the Small Magellanic Cloud wing tip might be currently forming dwarf spheroidal galaxies.
80. Southern Stars embedded in nebulosity
ID:
ivo://CDS.VizieR/VII/218
Title:
Southern Stars embedded in nebulosity
Short Name:
VII/218
Date:
21 Oct 2021
Publisher:
CDS
Description:
A survey of the Milky Way southward of the Palomar Sky Survey for the identification of reflection nebulae was carried out at the Cerro Tololo Inter-American Observatory in Chile. Plates in blue light were obtained at the Curtis Schmidt telescope covering a strip of plus or minus six degrees of the galactic equator. Red sensitive plates for comparison were also obtained with the same telescope covering the same area near the galactic plane. Observatory staff members and some students of the University of Toronto, Canada assisted in identifying stars embedded in nebulosity as shown by the plates. Although this catalogue roughly complements the Catalogue of Reflection Nebulae of van den Berg (1966AJ.....71..990V, Cat. <VII/21>), the region here surveyed is more narrowly confined to the galactic equator.