Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/91/347
- Title:
- A 5-GHz VLA Survey of the Galactic Plane
- Short Name:
- J/ApJS/91/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the VLA to survey the inner Galaxy (|b|<0.4{deg}, l=350-40{deg}) at 5GHz to a limiting sensitivity of between 2.5 and 10mJy. The survey has resulted in a catalog of 1272 discrete sources (including 100 sources outside the formal survey area) of which we have tentatively identified ~450 as ultracompact H II regions and ~45 as planetary nebulae. Approximately 30% of the radio sources are detected in the IRAS Point Source Catalog. The results confirm a scale height of only 30pc for ultracompact H II regions. We show that source lists generated from the IRAS Point Source Catalog alone suffer serious effects; the combination of the IRAS and radio surveys allows us to produce a much more complete census of the regions of massive star formation in our Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/711/619
- Title:
- {alpha}-element abundances in galactic PNe
- Short Name:
- J/ApJ/711/619
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present emission line strengths, abundances, and element ratios (X/O for Ne, S, Cl, and Ar) for a sample of 38 Galactic disk planetary nebulae (PNe) consisting primarily of Peimbert classification Type I. Spectrophotometry for these PNe incorporates an extended optical/near-IR range of 3600-9600{AA} including the [SIII] lines at 9069{AA} and 9532{AA}, setting this relatively large sample apart from typical spectral coverage. We have utilized Emission Line Spectrum Analyzer, a five-level atom abundance routine, to determine Te, Ne, ionization correction factors, and total element abundances, thereby continuing our work toward a uniformly processed set of data. With a compilation of data from >120 Milky Way PNe, we present results from our most recent analysis of abundance patterns in Galactic disk PNe. With a wide range of metallicities, galactocentric distances, and both Type I and non-Type I objects, we have examined the alpha elements against HII regions and blue compact galaxies (H2BCGs) to discern signatures of depletion or enhancement in PNe progenitor stars, particularly the destruction or production of O and Ne.
- ID:
- ivo://CDS.VizieR/J/AJ/142/139
- Title:
- A new catalog of HII regions in M31
- Short Name:
- J/AJ/142/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalog of HII regions in M31. The full disk of the galaxy (~24kpc from the galaxy center) is covered in a 2.2deg^2^ mosaic of 10 fields observed with the Mosaic Camera on the Mayall 4m telescope as part of the Local Group Galaxies survey.
- ID:
- ivo://CDS.VizieR/J/A+A/405/627
- Title:
- Angular dimensions of 312 planetary nebulae
- Short Name:
- J/A+A/405/627
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of direct measurements done on H{alpha} (or H{alpha}+[NII]) images of 312 planetary nebulae. For each planetary nebulae deconvolved FWHM and resolution size from Gaussian fit and from second-moment method and direct measurement at 10% level are presented.
- ID:
- ivo://CDS.VizieR/J/MNRAS/506/3540
- Title:
- ASKAP-EMU ESP LMC Radio Continuum Survey
- Short Name:
- J/MNRAS/506/3540
- Date:
- 17 Jan 2022 11:54:41
- Publisher:
- CDS
- Description:
- We present an analysis of a new 120 deg^2^ radio continuum image of the Large Magellanic Cloud (LMC) at 888MHz with a bandwidth of 288MHz and beam size of 13.9"x12.1", from the Australian Square Kilometre Array Pathfinder (ASKAP) processed as part of the Evolutionary Map of the Universe (EMU) survey. The median Root Mean Squared noise is 58uJy/beam. We present a catalogue of 54612 sources, divided over a Gold list (30866 sources) complete down to 0.5mJy uniformly across the field, a Silver list (22080 sources) reaching down to <0.2mJy and a Bronze list (1666 sources) of visually inspected sources in areas of high noise and/or near bright complex emission. We discuss detections of planetary nebulae and their radio luminosity function, young stellar objects showing a correlation between radio luminosity and gas temperature, novae and X-ray binaries in the LMC, and active stars in the Galactic foreground that may become a significant population below this flux level. We present examples of diffuse emission in the LMC (HII regions, supernova remnants, bubbles) and distant galaxies showcasing spectacular interaction between jets and intracluster medium. Among 14333 infrared counterparts of the predominantly background radio source population we find that star-forming galaxies become more prominent below 3mJy compared to active galactic nuclei.We combine the new 888MHz data with archival Australia Telescope Compact Array data at 1.4GHz to determine spectral indices; the vast majority display synchrotron emission but flatter spectra occur too. We argue that the most extreme spectral index values are due to variability.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A150
- Title:
- Astrometric data for 211 GAPN sample
- Short Name:
- J/A+A/630/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a catalogue of central stars of planetary nebulae (CSPN) with reliable distances and positions obtained from Gaia Data Release 2 (DR2) astrometry. Distances derived from parallaxes allow us to analyse the galactic distribution and estimate other parameters such as sizes, kinematical ages, bolometric magnitudes, and luminosities. Our objective is to analyse the information regarding distances together with other available literature data about photometric properties, nebular kinematics, and stellar effective temperatures to throw new light on this rapid and rather unknown evolutionary phase. We seek to understand how Gaia distances compare with other indirect methods commonly used and, in particular, with those derived from non-local thermodynamic equilibrium (non-LTE) models; how many planetary nebulae (PNe) populate the Galaxy; and how are they spatially distributed. We also aim to comprehend their intrinsic luminosities, range of physical sizes of the nebulae; how to derive the values for their kinematical ages; and whether those ages are compatible with those derived from evolutionary models. We considered all PNe listed in catalogues from different authors and in Hong Kong/AAO/Strasbourg/H{alpha} (HASH) database. By X-matching their positions with Gaia DR2 astrometry we were able to identify 1571 objects in Gaia second archive, for which we assumed distances calculated upon a Bayesian statistical approach. From those objects, we selected a sample of PNe with good quality parallax measurements and distance derivations, we which refer to as our Golden Astrometry PNe sample (GAPN), and obtained literature values of their apparent sizes, radial and expansion velocities, visual magnitudes, interstellar reddening, and effective temperatures. We found that the distances derived from DR2 parallaxes compare well with previous astrometric derivations of the United States Naval Observatory and Hubble Space Telescope, but that distances inferred from non-LTE model fitting are overestimated and need to be carefully reviewed. From literature apparent sizes, we calculated the physical radii for a subsample of nebulae that we used to derive the so-called kinematical ages, taking into account literature expansion velocities. Luminosities calculated with DR2 distances were combined with literature central stars Teff values in a Hertzsprung-Russell (HR) diagram to infer information on the evolutionary status of the nebulae. We compared their positions with updated evolutionary tracks finding a rather consistent picture. Stars with the smallest associated nebular radii are located in the flat luminosity region of the HR diagram, while those with the largest radii correspond to objects in a later stage, getting dimmer on their way to become a white dwarf. Finally, we commented on the completeness of our catalogue and calculated an approximate value for the total number of PNe in the Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A76
- Title:
- Automatic stellar spectral classification
- Short Name:
- J/A+A/538/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of a project aimed at deriving extinction-distances for thirty-five planetary nebulae, spectra of a few thousand stars were analyzed to determine their spectral type and luminosity class. We present here the automatic spectral classification process used to classify stellar spectra. This system can be used to classify any other stellar spectra with similar or higher signal-to-noise ratios. Spectral classification was performed using a system of artificial neural networks that were trained with a set of line-strength indices selected among the spectral lines most sensitive to temperature and the best luminosity tracers. The training and validation processes of the neural networks are discussed and the results of additional validation probes, designed to ensure the accuracy of the spectral classification, are presented.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/2118
- Title:
- Binarity in planetary nebula central stars
- Short Name:
- J/MNRAS/428/2118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We still do not know what causes aspherical planetary nebula (PN) morphologies. A plausible hypothesis is that they are due to the presence of a close stellar or substellar companion. So far, only ~40 binary central stars of PN have been detected, almost all of them with such short periods that their binarity is revealed by photometric variability. Here we have endeavoured to discover binary central stars at any separation, thus determining the unbiased binary fraction of central stars of PN. This number, when compared to the binary fraction of the presumed parent population, can give a first handle on the origin of PN. By detecting the central stars in the I band we have searched for cool companions.
- ID:
- ivo://CDS.VizieR/J/A+A/561/A8
- Title:
- Binary central stars of SMC PNe
- Short Name:
- J/A+A/561/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Optical Gravitational Lensing Experiment (OGLE), originally designed to search for microlensing events, provides a rich and uniform data set suitable for studying the variability of certain types of objects. We used the OGLE data to study the photometry of central stars of planetary nebulae (PNe) in the Small Magellanic Cloud (SMC). In particular, we searched for close binary central stars with the aim to constrain the binary fraction and period distribution in the SMC. We also searched for PNe mimics and removed them from the PNe sample. We identified 52 counterparts of PNe in the SMC in the I-band images from the OGLE-II and OGLE-III surveys. We analysed the time-series photometry of the PNe. Spectra of the photometric variables were obtained to constrain the nature of the objects or search for additional evidence for binarity. Eight variables were found. Of these, seven objects are PNe mimics, including one symbiotic star candidate. One close binary central star of PN with a period of 1.15 or 2.31 day was discovered. The obtained binary fraction for the SMC PNe and the observational biases are discussed in terms of the OGLE observations.
