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Start Over Subject nebulae Subject spectroscopy
1. ATCA Survey of Sagittarius B2 at 7mm
ID:
ivo://CDS.VizieR/J/MNRAS/452/3969
Title:
ATCA Survey of Sagittarius B2 at 7mm
Short Name:
J/MNRAS/452/3969
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a 30-50GHz survey of Sagittarius B2(N) conducted with the Australia Telescope Compact Array (ATCA) with 5 - 10 arcsec resolution. We analyze the spectra towards three HII regions that have foreground molecular gas in Sgr B2. Towards the most line-dense region, we detect >500 spectral line components, >90% of which are assigned to H and He recombination lines and 53 firmly identified molecular species (not including isotopologues). The data reveal extremely subthermally excited molecular gas in Sgr B2 absorbing against the continuum background, as well as molecular line emission from two hot cores in Sgr B2(N). They also also contain line-of-sight absorption by ~15 molecules observed in translucent gas in the Galactic Center, bar, and intervening spiral arm clouds, revealing the complex chemistry and clumpy structure of this gas. Formamide (NH_2_CHO) is detected for the first time in a translucent cloud.
2. Catalog of PNe in NGC 4697
ID:
ivo://CDS.VizieR/J/ApJS/175/522
Title:
Catalog of PNe in NGC 4697
Short Name:
J/ApJS/175/522
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of 535 planetary nebulae (PNs) discovered in the flattened elliptical galaxy NGC 4697, using the FORS1 Cassegrain spectrograph of the Very Large Telescope of the European Southern Observatory at Cerro Paranal, Chile. The catalog provides positions [(x,y)-coordinates relative to the center of light of NGC 4697, as well as {alpha},{delta}] and, for almost all PNs, the magnitude m(5007) and the heliocentric radial velocity in km/s.
3. 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.
4. 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.
5. Gas and dust in star-forming region rho OphA
ID:
ivo://CDS.VizieR/J/A+A/608/A133
Title:
Gas and dust in star-forming region rho OphA
Short Name:
J/A+A/608/A133
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate to what degree local physical and chemical conditions are related to the evolutionary status of various objects in star-forming media. rho Oph A displays the entire sequence of low-mass star formation in a small volume of space. Using spectrophotometric line maps of H_2_, H_2_O, NH_3_, N_2_H^+^, O_2_, OI, CO, and CS, we examine the distribution of the atomic and molecular gas in this dense molecular core. The physical parameters of these species are derived, as are their relative abundances in rho Oph A. Using radiative transfer models, we examine the infall status of the cold dense cores from their resolved line profiles of the ground state lines of H_2_O and NH_3_, where for the latter no contamination from the VLA 1623 outflow is observed and line overlap of the hyperfine components is explicitly taken into account. The stratified structure of this photon dominated region (PDR), seen edge-on, is clearly displayed. Polycyclic aromatic hydrocarbons (PAHs) and OI are seen throughout the region around the exciting star S1. At the interface to the molecular core 0.05pc away, atomic hydrogen is rapidly converted into H_2_, whereas OI protrudes further into the molecular core. This provides oxygen atoms for the gas-phase formation of O_2_ in the core SM1, where X(O_2_)~5x10^-8^. There, the ratio of the O_2_ to H_2_O abundance [X(H_2_O)~5x10^-9^] is significantly higher than unity. Away from the core, O_2_ experiences a dramatic decrease due to increasing H_2_O formation. Outside the molecular core, on the far side as seen from S1, the intense radiation from the 0.5pc distant early B-type star HD147889 destroys the molecules. Towards the dark core SM1, the observed abundance ratio X(O_2_)/X(H_2_O)>1, which suggests that this object is extremely young, which would explain why O_2_ is such an elusive molecule outside the solar system.
6. Gas and dust in the star-forming region rho OphA
ID:
ivo://CDS.VizieR/J/A+A/578/A131
Title:
Gas and dust in the star-forming region rho OphA
Short Name:
J/A+A/578/A131
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using mapping observations of the very dense rho Oph A core, we examined standard 1D and non-standard 3D methods to analyse data of far-infrared and submillimeter continuum radiation. The resulting dust surface density distribution can be compared to that of the gas. The latter was derived from the analysis of accompanying molecular line emission, observed with Herschel from space and with APEX from the ground. As a gas tracer we used N_2_H^+^, which is believed to be much less sensitive to freeze-out than CO and its isotopologues. Radiative transfer modelling of the N_2_H^+^(J=3-2) and (J=6-5) lines with their hyperfine structure explicitly taken into account provides solutions for the spatial distribution of the column density N(H2), hence the surface density distribution of the gas. The gas-to-dust mass ratio is varying across the map, with very low values in the central regions around the core SM1. The global average, =88, is not far from the canonical value of 100, however. In rho Oph A, the exponent beta of the power-law description for the dust opacity exhibits a clear dependence on time, with high values of 2 for the envelope-dominated emission in starless Class-1 sources to low values close to 0 for the disk-dominated emission in ClassIII objects. beta assumes intermediate values for evolutionary classes in between. Since beta is primarily controlled by grain size, grain growth mostly occurs in circumstellar disks. The spatial segregation of gas and dust, seen in projection toward the core centre, probably implies that, like C^18^O, also N_2_H^+^ is frozen onto the grains.
7. LMC & SMC PNe optical spectroscopy. I
ID:
ivo://CDS.VizieR/J/ApJS/75/407
Title:
LMC & SMC PNe optical spectroscopy. I
Short Name:
J/ApJS/75/407
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present optical spectroscopy in the range 3300-7400A for a total of 30 planetary nebulae in the LMC and 11 in the SMC, with measurements of line intensities down to ~1% of H{beta}. Agreement with other authors is on the whole excellent, especially for lines >+10%-20% of H{beta}. Reddening estimates from Balmer line ratios have been determined, and the line intensities dereddened accordingly. Nebular [O III] electron temperature and, where measurable, [N II] temperatures and [S II] densities are given. [O II] electron densities are recalculated using appropriate electron temperatures. A number of spectra exhibit interesting spectral features (including symbiotic-type profiles, unidentified emission lines, and nonsimple Balmer decrements). These objects are discussed in some detail. Zanstra temperatures are derived for a total of 25 objects possessing detectable stellar continua. These temperatures are in agreement with the few published values from various methods, and preliminary photoionization modeling of this sample. The homogeneity and size of the sample make it possible to investigate several interesting correlations between measured parameters.
8. LMC & SMC PNe optical spectroscopy. II
ID:
ivo://CDS.VizieR/J/ApJS/76/1085
Title:
LMC & SMC PNe optical spectroscopy. II
Short Name:
J/ApJS/76/1085
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present optical spectroscopy in the range 3300-7400A for a total of 37 planetary nebulae in the LMC and seven in the SMC. Together with the object from the first paper in the series (1991ApJS...75..407M), we now have accurate emission-line intensities down to a few percent of H{beta} for 77 nebulae in the Magellanic Clouds. Agreement with other authors is excellent. Reddening estimates from Balmer line ratios have been determined, and the line intensities have been dereddened accordingly. Nebular [O III] electron temperature and, where measurable, [S II] densities, are derived. [O II] electron densities are recalculated using appropriate electron temperatures. The [S II] and [O II] electron densities correlate well, with n_e_([O II])>n_e_([S II]). Zanstra temperatures are in derived for 22 objects possessing detectable stellar continua. These temperatures are in agreement with photoionization modeling of this sample.
9. LMC & SMC PNe optical spectroscopy. III
ID:
ivo://CDS.VizieR/J/ApJS/83/87
Title:
LMC & SMC PNe optical spectroscopy. III
Short Name:
J/ApJS/83/87
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present optical spectroscopy in the range 3300-7400A for a total of 52 planetary nebulae in the Large Magellanic Cloud (LMC) and 18 in the Small Magellanic Cloud (SMC). Together with the object from the first (1991ApJS...75..407M) and second (1991ApJS...76.1085M) papers, we now have accurate emission-line intensities for a total of 147 nebulae in the Magellanic Clouds. This sample contains a large selection of objects of low luminosity, with measurements of line intensities down to ~10% of H{beta}. Brighter objects have line intensities measured down to ~2% of H{beta}. Agreement with other authors is generally very good, especially for lines greater than approximately 10% of H{beta}. Reddening estimates from Balmer line ratios have been determined: unreddened and reddened line intensities are tabulated.
10. M17-SW datacubes in C and CO lines
ID:
ivo://CDS.VizieR/J/A+A/575/A9
Title:
M17-SW datacubes in C and CO lines
Short Name:
J/A+A/575/A9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We probe the column densities and masses traced by the ionized [CII] and neutral [CI] atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [CI] and low-J CO lines toward the star-forming region M17 SW. We mapped a 4.1pcx4.7pc region in the [CI] 609{mu}m line using the APEX telescope, as well as the CO isotopologues with the IRAM 30m telescope. Data are analyzed based on velocity channel maps that are 1km/s wide. We correlate their spatial distribution with that of the [CII] map obtained with SOFIA/GREAT. Optically thin approximations were used to estimate the column densities of [CI] and [CII] in each velocity channel.

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