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21. Cobalt emission in nebular phase spectra
ID:
ivo://CDS.VizieR/J/MNRAS/454/3816
Title:
Cobalt emission in nebular phase spectra
Short Name:
J/MNRAS/454/3816
Date:
21 Oct 2021
Publisher:
CDS
Description:
The light curves of Type Ia supernovae (SNe Ia) are powered by the radioactive decay of ^56^Ni to ^56^Co at early times, and the decay of ^56^Co to ^56^Fe from ~60 d after explosion. We examine the evolution of the [CoIII] {lambda}5893 emission complex during the nebular phase for SNe Ia with multiple nebular spectra and show that the line flux follows the square of the mass of ^56^Co as a function of time. This result indicates both efficient local energy deposition from positrons produced in ^56^Co decay and long-term stability of the ionization state of the nebula. We compile SN Ia nebular spectra from the literature and present 21 new late-phase spectra of 7 SNe Ia, including SN 2014J. From these we measure the flux in the [CoIII] {lambda}5893 line and remove its well-behaved time dependence to infer the initial mass of ^56^Ni (M_Ni_) produced in the explosion. We then examine ^56^Ni yields for different SN Ia ejected masses (M_ej_ - calculated using the relation between light-curve width and ejected mass) and find that the ^56^Ni masses of SNe Ia fall into two regimes: for narrow light curves (low stretch s~0.7-0.9), M_Ni_ is clustered near M_Ni_~0.4M_{sun}_ and shows a shallow increase as M_ej_ increases from ~1 to 1.4M_{sun}_; at high stretch, M_ej_ clusters at the Chandrasekhar mass (1.4M_{sun}_) while M_Ni_ spans a broad range from 0.6 to 1.2M_{sun}_. This could constitute evidence for two distinct SN Ia explosion mechanisms.
22. CO(2-1) maps of IRAS 18059-3211
ID:
ivo://CDS.VizieR/J/A+A/483/839
Title:
CO(2-1) maps of IRAS 18059-3211
Short Name:
J/A+A/483/839
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the nature of Gomez's Hamburger (IRAS 18059-3211), a nebula that has been proposed to be a post-AGB object. Such a classification has not been confirmed; instead, we argue that it will be a key object in the study of disks rotating around young stars. We present high-resolution SMA maps of CO J=2-1 (230.538GHz) in Gomez's Hamburger. The data are analyzed by means of a code that simulates the emission of a nebula showing a variety of physical conditions and kinematics. Our observations clearly show that the CO emitting gas in Gomez's Hamburger forms a spectacular disk in keplerian rotation. Model calculations undoubtedly confirm this result. The central (mainly stellar) mass is found to be high, ~4 solar masses for a distance of 500pc. The mass and (relatively low) luminosity of the source are, independent of the assumed distance, very different from those possible in evolved stars. This object is probably transitional between the pre-MS and MS phases, still showing interstellar material around the central star or stellar system.
23. Combined ArTeMiS+SPIRE 350um image of NGC6334
ID:
ivo://CDS.VizieR/J/A+A/592/A54
Title:
Combined ArTeMiS+SPIRE 350um image of NGC6334
Short Name:
J/A+A/592/A54
Date:
21 Oct 2021
Publisher:
CDS
Description:
Herschel observations of nearby molecular clouds suggest that interstellar filaments and prestellar cores represent two fundamental steps in the star formation process. The observations support a picture of low-mass star formation according to which filaments of ~0.1pc width form first in the cold interstellar medium, probably as a result of large-scale compression of interstellar matter by supersonic turbulent flows, and then prestellar cores arise from gravitational fragmentation of the densest filaments. Whether this scenario also applies to regions of high-mass star formation is an open question, in part because the resolution of Herschel is insufficient to resolve the inner width of filaments in the nearest regions of massive star formation. In an effort to characterize the inner width of filaments in high-mass star-forming regions, we imaged the central part of the NGC 6334 complex at a resolution higher by a factor of >3 than Herschel at 350microns. We used the large-format bolometer camera ArTeMiS on the APEX telescope and combined the high-resolution ArTeMiS data at 350microns with Herschel/HOBYS data at 70-500microns to ensure good sensitivity to a broad range of spatial scales. This allowed us to study the structure of the main narrow filament of the complex with a resolution of 8" or <0.07pc at d~1.7kpc. Our study confirms that this filament is a very dense, massive linear structure with a line mass ranging from ~500M_{sun}_/pc to ~2000M_{sun}_/pc over nearly 10pc. It also demonstrates for the first time that its inner width remains as narrow as W~0.15+/-0.05pc all along the filament length, within a factor of <2 of the characteristic 0.1pc value found with Herschel for lower-mass filaments in the Gould Belt. While it is not completely clear whether the NGC 6334 filament will form massive stars in the future, it is two to three orders of magnitude denser than the majority of filaments observed in Gould Belt clouds, and has a very similar inner width. This points to a common physical mechanism for setting the filament width and suggests that some important structural properties of nearby clouds also hold in high-mass star-forming regions.
24. Dark Nebulae and Globules for l=240-360deg
ID:
ivo://CDS.VizieR/VII/68A
Title:
Dark Nebulae and Globules for l=240-360deg
Short Name:
VII/68A
Date:
21 Oct 2021
Publisher:
CDS
Description:
(adapted from Anne C. Raugh, NASA STI-T-1-5810-508-86) The catalog is a compilation of data gleened from a study of the European Southern Observatory Quick Blue Survey (ESO(b)) and SRC-J Sky Atlas on 489 dark clouds and 331 globules. The data compiled include position, size, opacity and morphological classification (in the system of van den Bergh, 1972). Also included is a FITS file containing a 500x1400 pixel map of the survey area.
25. Diffuse emissions in Carina nebula
ID:
ivo://CDS.VizieR/J/A+A/423/579
Title:
Diffuse emissions in Carina nebula
Short Name:
J/A+A/423/579
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of mapping observations with ISO of [OI]63{mu}m, 145{mu}m, [NII]122{mu}m, [CII]158{mu}m, [SiII]35{mu}m, and H_2_9.66{mu}m line emissions for the Carina nebula, an active star-forming region in the Galactic plane. The observations were made for the central 40'x20' area of the nebula, including the optically bright HII region and molecular cloud lying in front of the ionized gas. Around the center of the observed area is the interface between the HII region and the molecular cloud which creates a typical photodissociation region (PDR).
26. Distance measurements of Lynds Nebulae
ID:
ivo://CDS.VizieR/J/A+AS/113/325
Title:
Distance measurements of Lynds Nebulae
Short Name:
J/A+AS/113/325
Date:
21 Oct 2021
Publisher:
CDS
Description:
A literature search has been carried out in order to obtain a distance table for the Lynds galactic nebulae which in the main have been cited in Astronomy and Astrophysics Abstracts between 1980 and 1984. Inevitably this list cannot be without omission and a request is made for any further information which could lead to the publication of a more complete compilation.
27. Dynamics of ionized and neutral gas in M8
ID:
ivo://CDS.VizieR/J/A+A/604/A135
Title:
Dynamics of ionized and neutral gas in M8
Short Name:
J/A+A/604/A135
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopic study of the dynamics of the ionized and neutral gas throughout the Lagoon nebula (M8), using VLT/FLAMES data from the Gaia-ESO Survey. We explore the connections between the nebular gas and the stellar population of the associated star cluster NGC6530. We characterize through spectral fitting emission lines of H{alpha}, [NII] and [SII] doublets, [OIII], and absorption lines of sodium D doublet, using data from the FLAMES/Giraffe and UVES spectrographs, on more than 1000 sightlines towards the entire face of the Lagoon nebula. Gas temperatures are derived from line-width comparisons, densities from the [SII] doublet ratio, and ionization parameter from H{alpha}/[NII] ratio. Although doubly-peaked emission profiles are rarely found, line asymmetries often imply multiple velocity components along the same line of sight. This is especially true for the sodium absorption, and for the [OIII] lines. Spatial maps for density and ionization are derived, and compared to other known properties of the nebula and of its massive stars 9 Sgr, Herschel 36 and HD 165052 which are confirmed to provide most of the ionizing flux. The detailed velocity fields across the nebula show several expanding shells, related to the cluster NGC6530, the O stars 9 Sgr and Herschel 36, and the massive protostar M8East-IR. The origins of kinematical expansion and ionization of the NGC6530 shell appear to be different. We are able to put constrains on the line-of-sight (relative or absolute) distances between some of these objects and the molecular cloud. The large obscuring band running through the middle of the nebula is being compressed by both sides, which might explain its enhanced density. We also find an unexplained large-scale velocity gradient across the entire nebula. At larger distances, the transition from ionized to neutral gas is studied using the sodium lines.
28. Einstein survey of the Orion nebula region
ID:
ivo://CDS.VizieR/J/ApJ/437/361
Title:
Einstein survey of the Orion nebula region
Short Name:
J/ApJ/437/361
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have analyzed archival Einstein Observatory images of a roughly 4.5 square degree region centered on the Orion Nebula. In all, 245 distinct X-ray sources have been detected in six High Resolution Imager (HRI) and 17 Imaging Proportional Counter (IPC) observations. An optical database of over 2700 stars has been assembled to search for candidate counterparts to the X-ray sources. Roughly half the X-ray sources are identified with a single Orion Nebula cluster member. The 10 main-sequence O6-B5 cluster stars detected in Orion have X-ray activity levels comparable to field O and B stars. X-ray emission has also been detected in the direction of four main-sequence late-B and early-A type stars. Since the mechanisms producing X-rays in late-type coronae and early-type winds cannot operate in the late-B and early-A type atmospheres, we argue that the observed X-rays, with L_X_~3x10^30^ergs/s, are probably produced in the coronae of unseen late-type binary companions. Over 100 X-ray sources have been associated with late-type pre-main sequence stars.
29. Emission Lines of the Planetary Nebulae
ID:
ivo://CDS.VizieR/III/203
Title:
Emission Lines of the Planetary Nebulae
Short Name:
III/203
Date:
21 Oct 2021
Publisher:
CDS
Description:
The relative intensities of emission lines in the spectra of 32 planetary nebulae in the 3700-7300{AA} region are presented. The spectral observations have been carried out using slit spectrograph with three-cascades image-tube, attached to 70-cm reflector (Alma-Ata). The spectral region is 3700-8500{AA}. The dispersion in the range of 12-200{AA}/mm. The spectral resolution is 0.8-13{AA} in dependence on the dispersion. The errors are less than 10% for the bright lines, 10-15% for the moderate lines and 25-50% for the faintest lines. All measured line intensities were normalised to I(Hbeta)=100.
30. Extended red emission in IC59 and IC63
ID:
ivo://CDS.VizieR/J/MNRAS/469/4933
Title:
Extended red emission in IC59 and IC63
Short Name:
J/MNRAS/469/4933
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analysed new wide-field, wide- and narrow-band optical images of IC 59 and IC 63, two nebulae that are externally illuminated by the early B-star {gamma} Cas, with the objective of mapping the extended red emission (ERE), a dust-related photoluminescence process that is still poorly understood, in these two clouds. The spatial distribution of the ERE relative to the direction of the incident radiation and relative to other emission processes, whose carriers and excitation requirements are known, provides important constraints on the excitation of the ERE. In both nebulae, we find the ERE intensity to peak spatially well before the more extended distribution of mid-infrared emission in the unidentified infrared bands, supporting earlier findings that point towards far-ultraviolet (11<E_photon_<13.6eV) photons as the source of ERE excitation. The band-integrated absolute intensities of the ERE in IC 59 and IC 63 measured relative to the number density of photons available for ERE excitation are lower by about two orders of magnitude compared to ERE intensities observed in the high-latitude diffuse interstellar medium. This suggests that the lifetime of the ERE carriers is significantly reduced in the more intense radiation field prevailing in IC 59 and IC 63, pointing towards potential carriers that are only marginally stable against photoprocessing under interstellar conditions. A model involving isolated molecules or molecular ions, capable of inverse internal conversion and recurrent fluorescence, appears to provide the most likely explanation for our observational results.