- ID:
- ivo://CDS.VizieR/J/A+A/459/L13
- Title:
- A composite HII region luminosity function
- Short Name:
- J/A+A/459/L13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Statistical properties of HII region populations in disk galaxies yield important clues to the physics of massive star formation. We present a set of HII region catalogues and luminosity functions for a sample of 56 spiral galaxies in order to derive the most general form of their luminosity function. HII region luminosity functions were derived for individual galaxies which, after photometric calibration, were summed to form a total luminosity function comprising 17797 HII regions from 53 galaxies.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/446/274
- Title:
- A deep catalogue of classical Be stars
- Short Name:
- J/MNRAS/446/274
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of 247 photometrically and spectroscopically confirmed fainter classical Be stars (13<r<16) in the direction of the Perseus Arm of the Milky Way (1{deg}<b<+4{deg}, 120{deg}<l<140{deg}). The catalogue consists of 181 IPHAS-selected new classical Be stars, in addition to 66 objects that we studied in our previous work more closely, and three stars identified as classical Be stars in earlier work. This study more than doubles the number known in the region. Photometry spanning 0.6-5um, spectral types, and interstellar reddenings are given for each object. The spectral types were determined from low-resolution spectra ({lambda}/{Delta}_{lambda}~800-2000), to a precision of 1-3 subtypes. The interstellar reddenings are derived from the (r-i) colour, using a method that corrects for circumstellar disc emission. The colour excesses obtained range from E(B-V)=0.3 up to 1.6 a distribution that modestly extends the range reported in the literature for Perseus-Arm open clusters. For around half the sample, the reddenings obtained are compatible with measures of the total sightline Galactic extinction. Many of these are likely to lie well beyond the Perseus Arm.
- 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/622/A156
- Title:
- A search for accreting young companions
- Short Name:
- J/A+A/622/A156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, our understanding of giant planet formation progressed substantially. There have even been detections of a few young protoplanet candidates still embedded in the circumstellar disks of their host stars. The exact physics that describes the accretion of material from the circumstellar disk onto the suspected circumplanetary disk and eventually onto the young, forming planet is still an open question. We seek to detect and quantify observables related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the result of interactions with planets. We analyzed observations of six young stars and their surrounding environments with the SPHERE/ZIMPOL instrument on the Very Large Telescope (VLT) in the H{alpha} filter (656nm) and a nearby continuum filter (644.9nm). We redetect the known accreting M-star companion HD142527 B with the highest published signal to noise to date in both H{alpha} and the continuum. No other companions are detected. We analyzed observations of six young stars (age 3.5-10Myr) and their surrounding environments with the SPHERE/ZIMPOL instrument on the Very Large Telescope (VLT) in the H{alpha}filter (656nm) and a nearby continuum filter (644.9nm). We applied several point spread function (PSF) subtraction techniques to reach the highest possible contrast near the primary star, specifically investigating regions where forming companions were claimed or have been suggested based on observed disk morphology.
- ID:
- ivo://CDS.VizieR/J/AJ/156/61
- Title:
- A study of the H{alpha} variability of Be stars
- Short Name:
- J/AJ/156/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the results of 4 years of high-resolution spectral observations of 69 emission-line stars, 54 of them being newly discovered sources. We classified the stars on the basis of their position in the two-color IR diagram and some additional criteria: shape and width of the H{alpha} profile, presence of He lines, proper motion and parallax, membership to open cluster and associations. Sixty of our targets turned out to be Be stars. We also found four late giants, four pre-MS stars, and one late dwarf. The H{alpha} emission profiles of our Be stars range from single peaked to typical shell profiles that can also be highly asymmetric or single-peaked profiles with a narrow absorption core. The emission profiles appear almost constant with time or highly variable in intensity and in their V/R ratio. The detected long-term variability of the H{alpha} emission is important for investigating the on/off switch phenomenon of Be stars. Our study led to an increase of the number of the emission-line stars of 16 open clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A28
- Title:
- ATLAS3D H{alpha} imaging of early-type galaxies
- Short Name:
- J/A+A/611/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The traditional knowledge of the mechanisms that caused the formation and evolution of early-type galaxies (ETG) in a hierarchical universe was challenged by the unexpected finding by ATLAS^3D^ that 86% of the ETGs show signs of a fast-rotating disk at their interior. This implies a common origin of most spiral galaxies, followed by a quenching phase, while only a minority of the most massive systems are slow rotators and were likely to be the products of merger events. Our aim is to improve our knowledge on the content and distribution of ionized hydrogen and their usage to form stars in a representative sample of ETGs for which the kinematics and detailed morphological classification were known from ATLAS^3D^. Methods. Using narrow-band filters centered on the redshifted H{alpha} line along with a broad-band (r-Gunn) filter to recover the stellar continuum, we observed or collected existing imaging observations for 147 ETGs (including members of the Virgo cluster) that are representative of the whole ATLAS3D survey. Fifty-five ETGs (37%) were detected in the H{alpha} line above our detection threshold, (EW(H{alpha})<=-1{AA}), and 21 harbor a strong source (EW(H{alpha})<=-5{AA}). The strong H{alpha} emitters appear associated with mostly low-mass (M*~10^10^M_{sun}_) S0 galaxies that contain conspicuous stellar and gaseous discs. These harbor significant star formation at their interior, including their nuclei. The weak H{alpha} emitters are almost one order of magnitude more massive, contain gas-poor discs and harbor an AGN at their centers. Their emissivity is dominated by [NII] and does not imply star formation. The 92 undetected ETGs constitute the majority in our sample and are gas-free systems that lack a disc and exhibit passive spectra even in their nuclei. These pieces of evidence reinforce the conclusion made previously that the evolution of ETGs followed the secular channel for the less massive systems and the dry merging channel for the most massive galaxies at the center of clusters of galaxies.
- ID:
- ivo://CDS.VizieR/J/other/NewA/56.28
- Title:
- Be stars in MC star clusters NIR properties
- Short Name:
- J/other/NewA/56.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magellanic Clouds are the nearby galaxies which are ideal to study the properties of metal poor stellar population. In this study, we explore the near-IR properties of optically identified classical Be stars in 19 star clusters in the Magellanic Clouds. From an optically identified sample of 835 Be stars we obtained the J, H, K magnitudes of 389 stars from the IRSF MCPS catalog. Among these, 247 stars (36.4%) are found in 9 clusters in the Large Magellanic Cloud and 142 stars (55.5%) in 10 clusters in the Small Magellanic Cloud. After correcting for reddening, we studied their NIR properties in the (H-K)_0_ vs (J-H)_0_ diagram. We identified 14 stars with abnormally large near IR excesses, which were removed from the analysis, there by restricting our study to 355 classical Be stars. We propose an extended area in the near-IR (H-K)_0_ vs (J-H)_0_ diagram as the diagnostic location of Classical Be stars in the Magellanic Clouds. We identified 14 stars to have near-IR excess, higher than those seen in classical Be stars. From the analysis based on spectral energy distribution and luminosity estimate, we found that 8 candidate Be stars may be Herbig Ae/Be stars. We identified a new sample of 6 sgB[e] stars, which when added to the sparse existing sample of 15 sgB[e] stars in the Magellanic Clouds can provide insight to understand the evolutionary link between sgB[e] stars and Luminous Blue variables.
- ID:
- ivo://CDS.VizieR/J/ApJS/147/29
- Title:
- BRHalpha data of blue compact dwarf galaxies
- Short Name:
- J/ApJS/147/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present B, R, and H{alpha} images for a total of 114 nearby galaxies (v_helio_<4000km/s) that, with exception of nine objects, are classified as blue compact dwarfs (BCDs). BR integrated magnitudes, H{alpha} fluxes and H{alpha} equivalent widths for all the objects in the sample are presented.
- ID:
- ivo://CDS.VizieR/J/A+A/376/144
- Title:
- BV(RI)_C_H{alpha} photometry of NGC 663
- Short Name:
- J/A+A/376/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new BV(RI)_C_H{alpha} photometry of the young open cluster NGC 663. The H{alpha} photometry is complete down to magnitude R_C_=15.4, corresponding to spectral type A5 for the cluster members. This allows detection of mild and strong H{alpha} emission in all B-type stars in the cluster. In addition to the 22 Be stars known in the observed field of NGC 663, we discovered four new faint stars of this type. We find that Be stars in NGC 663 cover the whole range of the B spectral type. They are, however, most populous among stars with spectral types falling in the range between B0 and B3, where their fraction amounts to 31+/-8%. Among B-type stars later than B3, Be stars are much less abundant: only 7 out of 101 observed stars, that is, 7+/-3%, were detected. About 70% of the observed Be stars in NGC 663 show detectable variations of light. In the time interval covered by our observations, the ranges of the largest variations reach 0.4mag in the I_C_ band. By means of the isochrone fitting, we derived the cluster distance of 2.1kpc, age of 20-25Myr, and the mean colour excess E(R-I)_C_=0.54mag, with a ~0.1mag scatter due to differential reddening.
- ID:
- ivo://CDS.VizieR/J/AJ/123/304
- Title:
- BV(RI)_C_JHK H{alpha} photometry in IC 5146
- Short Name:
- J/AJ/123/304
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The B0V star BD+46 3474 lies near the front surface of a dense molecular cloud and illuminates the emission/reflection nebula IC 5146. The HAeBe variable BD +46 3471 is embedded in the same cloud, about 10' (3.5pc) away. CCD photometry in BV(RI)_C_ (to V=22) and in JHK (to about K=16.5) has been obtained for the young clusters surrounding each of these two bright stars. Some 100 emission-H{alpha} stars brighter than R=20.5 have been found in the area, most of them in IC 5146. (Among these are two that have spectra resembling a high-excitation Herbig-Haro [HH] object plus a stellar continuum).
