- ID:
- ivo://CDS.VizieR/J/A+A/636/A48
- Title:
- VMC Survey. XXXVII. MC AGB stars
- Short Name:
- J/A+A/636/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variability is a key property of stars on the asymptotic giant branch (AGB). Selection criteria are derived based on colour-colour and colour-magnitude diagrams from the combination of VISTA Magellanic Cloud (VMC) survey, Spitzer IRAC, and AllWISE data. After eliminating LPVs with known periods shorter than 450 days, a sample of 1299 candidate obscured AGB stars is selected. K-band LCs are constructed combining the epoch photometry available in the VMC survey with literature data, analysed for variability and fitted with a single period sine curve to derive mean magnitudes, amplitudes and periods. A subset of 254 stars are either new variables, or known variables where the period we find is better determined than the literature value, or longer than 1000 days. The spectral energy distributions (SEDs) of these stars are fitted to a large number of templates. For this purpose the SEDs and Spitzer IRS spectra of some non-AGB stars (Be stars, Hii regions and young stellar objects [YSOs]) are also fitted to have templates of the most likely contaminants in the sample. A sample of 217 likely LPVs is found. Thirty-four stars have periods longer than 1000 days although some of them have alternative shorter periods.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/849/149
- Title:
- VMC XXVII. Young stellar structures in the LMC
- Short Name:
- J/ApJ/849/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star formation is a hierarchical process, forming young stellar structures of star clusters, associations, and complexes over a wide range of scales. The star-forming complex in the bar region of the Large Magellanic Cloud is investigated with upper main-sequence stars observed by the VISTA Survey of the Magellanic Clouds. The upper main-sequence stars exhibit highly nonuniform distributions. Young stellar structures inside the complex are identified from the stellar density map as density enhancements of different significance levels. We find that these structures are hierarchically organized such that larger, lower-density structures contain one or several smaller, higher- density ones. They follow power-law size and mass distributions, as well as a lognormal surface density distribution. All these results support a scenario of hierarchical star formation regulated by turbulence. The temporal evolution of young stellar structures is explored by using subsamples of upper main-sequence stars with different magnitude and age ranges. While the youngest subsample, with a median age of log({tau}/yr)=7.2, contains the most substructure, progressively older ones are less and less substructured. The oldest subsample, with a median age of log({tau}/yr)=8.0, is almost indistinguishable from a uniform distribution on spatial scales of 30-300pc, suggesting that the young stellar structures are completely dispersed on a timescale of ~100Myr. These results are consistent with the characteristics of the 30 Doradus complex and the entire Large Magellanic Cloud, suggesting no significant environmental effects. We further point out that the fractal dimension may be method dependent for stellar samples with significant age spreads.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/3011
- Title:
- VVV high amplitude NIR variable stars
- Short Name:
- J/MNRAS/465/3011
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of 816 high-amplitude infrared variable stars ({Delta}K_s_>1mag) in 119deg^2^ of the Galactic mid-plane covered by the VISTA Variables in the Via Lactea (VVV) survey. Almost all are new discoveries and about 50 per cent are young stellar objects (YSOs). This provides further evidence that YSOs are the commonest high-amplitude infrared variable stars in the Galactic plane. In the 2010-2014 time series of likely YSOs, we find that the amplitude of variability increases towards younger evolutionary classes (class I and flat-spectrum sources) except on short time-scales (<25d) where this trend is reversed. Dividing the likely YSOs by light-curve morphology, we find 106 with eruptive light curves, 45 dippers, 39 faders, 24 eclipsing binaries, 65 long-term periodic variables (P>100d) and 162 short-term variables. Eruptive YSOs and faders tend to have the highest amplitudes and eruptive systems have the reddest spectral energy distribution (SEDs). Follow-up spectroscopy in a companion paper verifies high accretion rates in the eruptive systems. Variable extinction is disfavoured by the two epochs of colour data. These discoveries increase the number of eruptive variable YSOs by a factor of at least 5, most being at earlier stages of evolution than the known FUor and EXor types. We find that eruptive variability is at least an order of magnitude more common in class I YSOs than class II YSOs. Typical outburst durations are 1-4yr, between those of EXors and FUors. They occur in 3-6 per cent of class I YSOs over a 4yr time span.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A115
- Title:
- VVV: star formation and embedded clusters
- Short Name:
- J/A+A/562/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to locate previously unknown stellar clusters using the VISTA variables in the Via Lactea Survey (VVV) catalogue data. The method fits a mixture model of Gaussian densities and background noise and uses the expectation maximization algorithm to pre-filtered near-infrared survey stellar catalogue data; it was developed by the authors for the UKIDSS Galactic Plane Survey (GPS). The search located 88 previously unknown candidates, most of which are embedded stellar cluster candidates, and 39 previously unknown sites of star formation in the 562deg^2^ covered by VVV in the Galactic bulge and the southern disk.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A145
- Title:
- VVV Survey outer bulge RRab stars
- Short Name:
- J/A+A/591/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VISTA Variables in the Via Lactea (VVV) is a near-IR time-domain survey of the Galactic bulge and southern plane. One of the main goals of this survey is to reveal the 3D structure of the Milky Way through their variable stars. In particular, enormous numbers of RR Lyrae stars have been discovered in the inner regions of the bulge (-8{deg}<~b<~-1{deg}) by optical surveys such as OGLE and MACHO, but leaving an unexplored window of more than ~47 sq deg (-10.0{deg}<~l<~+10.7{deg} and -10.3{deg}<~b<~-8.0{deg}) observed by the VVV Survey. Our goal is to characterize the RR Lyrae stars in the outer bulge in terms of their periods, amplitudes, Fourier coefficients, and distances in order to evaluate the 3D structure of the bulge in this area. The distance distribution of RR Lyrae stars will be compared to that of red clump stars, which is known to trace a X-shaped structure, in order to determine whether these two different stellar populations share the same Galactic distribution. A search for RR Lyrae stars was performed in more than ~47 sq deg at low Galactic latitudes (-10.3{deg}<~b<~-8.0{deg}). In the procedure the {chi}^2^ value and analysis of variance (AoV) statistic methods were used to determine the variability and periodic features of the light curves, respectively. To prevent misclassifications, the analysis was performed only on the fundamental mode RR Lyrae stars (RRab) owing to similarities found in the near-IR light curve shapes of contact eclipsing binaries (W UMa) and first overtone RR Lyrae stars (RRc). On the other hand, the red clump stars of the same analyzed tiles were selected, and cuts in the color-magnitude diagram were applied and the maximum distance restricted to ~20kpc in order to construct a similar catalog in terms of distances and covered area compared to the RR Lyrae stars. We report the detection of more than 1000 RR Lyrae ab-type stars in the VVV Survey located in the outskirts of the Galactic bulge. A few of them are possibly associated with the Sagittarius Dwarf Spheroidal Galaxy. We calculated colours, reddening, extinction, and distances of the detected RR Lyrae stars in order to determine the outer bulge 3D structure. Our main result is that, at the low galactic latitudes mapped here, the RR Lyrae stars trace a centrally concentrated spheroidal distribution. This is a noticeably different spatial distribution to the one traced by red clump stars known to follow a bar and X-shaped structure. We estimate the completeness of our sample at 80% for K_s_<=15mag.
- ID:
- ivo://CDS.VizieR/J/A+A/410/597
- Title:
- Warm dust near methanol masers
- Short Name:
- J/A+A/410/597
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Continuum emission at 450 and 850{mu}m from warm dust has been mapped in the fields of 71 methanol masers. Within these fields lie 30 centimetre-wave radio continuum sources and an additional 13 methanol maser sites. Sub-mm emission is detected at all but one of the maser sites, confirming the association of methanol maser emission with deeply embedded objects. Measured bolometric luminosities confirm that methanol maser emission is an excellent signpost of high-mass star formation. Examples of nearby isolated maserless dust cores may be harbouring massive protostars at an earlier evolutionary stage.
- ID:
- ivo://CDS.VizieR/J/A+AS/70/95
- Title:
- Warm IRAS sources. I. AGN candidates
- Short Name:
- J/A+AS/70/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have previously shown that a blue (warm) 60 to 25{mu}m infrared colour provides a powerful parameter for discriminating between AGNs and normal galaxies and that the far-IR spectrum is therefore an efficient tool for finding new AGNs (de Grijp et al., 1985Natur.314..140D) Here we present a list of such AGN candidates based on warm IR sources from the IRAS Point Source Catalogue (PSC, Cat. II/125). Identification data and finding charts are also given. In addition the list of warm IRAS sources is supplemented by a compendium of data from the IRAS PSC on detected sources identified with previously known AGNs whose infrared spectra do not bring them within our colour selection criterion
1008. Warm IRAS sources. IV.
- ID:
- ivo://CDS.VizieR/J/A+AS/108/61
- Title:
- Warm IRAS sources. IV.
- Short Name:
- J/A+AS/108/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a list of objects observed to have extended line emission in our spectroscopic survey of infrared-warm AGN. Slit spectroscopic data were obtained for 225 galaxies identified with objects in our compendium of warm sources from the IRAS Point Source Catalog. Of these, 44 have spatially-resolved emission-line regions along the (arbitrarily placed) slit direction. Measured (projected) linear sizes of the ionized gas regions extend to >10kpc. In the case of the IRAS Seyfert galaxies the spatially extended line emission appears to have a lower ionization state than the nuclear emission. This contrasts with the warm IRAS starbust galaxies for which there is no significant difference between the ionization states of the nuclear and extended emission. For the starburst galaxies, there is a relation between the extent of star formation as seen at H{alpha} and the far-IR colors, with more compact bursts having "warmer" colors.
- ID:
- ivo://CDS.VizieR/J/AJ/156/295
- Title:
- Warm molecular hydrogen in nearby LIRGs
- Short Name:
- J/AJ/156/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mid-infrared molecular hydrogen (H_2_) emission is a powerful cooling agent in galaxy mergers and in radio galaxies; it is a potential key tracer of gas evolution and energy dissipation associated with mergers, star formation, and accretion onto supermassive black holes. We detect mid-IR H_2_ line emission in at least one rotational transition in 91% of the 214 Luminous Infrared Galaxies (LIRGs) observed with Spitzer as part of the Great Observatories All-sky LIRG Survey. We use H_2_ excitation diagrams to estimate the range of masses and temperatures of warm molecular gas in these galaxies. We find that LIRGs in which the IR emission originates mostly from the Active Galactic Nuclei (AGN) have about 100 K higher H_2_ mass-averaged excitation temperatures than LIRGs in which the IR emission originates mostly from star formation. Between 10% and 15% of LIRGs have H_2_ emission lines that are sufficiently broad to be resolved or partially resolved by the high-resolution modules of Spitzer's Infrared Spectrograph (IRS). Those sources tend to be mergers and contain AGN. This suggests that a significant fraction of the H_2_ line emission is powered by AGN activity through X-rays, cosmic rays, and turbulence. We find a statistically significant correlation between the kinetic energy in the H_2_ gas and the H_2_ to IR luminosity ratio. The sources with the largest warm gas kinetic energies are mergers. We speculate that mergers increase the production of bulk inflows leading to observable broad H_2_ profiles and possibly denser gas.
- ID:
- ivo://CDS.VizieR/J/ApJ/707/1
- Title:
- Water and Methanol masers in NGC 6334I(N)
- Short Name:
- J/ApJ/707/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-resolution, multi-wavelength study of the massive protostellar cluster NGC 6334 I(N) that combines new spectral line data from the Submillimeter Array (SMA) and VLA with a re-analysis of archival VLA continuum data, Two Micron All Sky Survey and Spitzer images. As shown previously, the brightest 1.3mm source SMA1 contains substructure at subarcsecond resolution, and we report the first detection of SMA1b at 3.6cm along with a new spatial component at 7mm (SMA1d). We find SMA1 (aggregate of sources a, b, c, and d) and SMA4 to be comprised of free-free and dust components, while SMA6 shows only dust emission. Our 1.5" resolution 1.3mm molecular line images reveal substantial hot-core line emission toward SMA1 and to a lesser degree SMA2. We find CH_3_OH rotation temperatures of 165+/-9K and 145+/-12K for SMA1 and SMA2, respectively. We estimate a diameter of 1400AU for the SMA1 hot-core emission, encompassing both SMA1b and SMA1d, and speculate that these sources comprise a >~800AU separation binary that may explain the previously suggested precession of the outflow emanating from the SMA1 region. Compact line emission from SMA4 is weak, and none is seen toward SMA6. The LSR velocities of SMA1, SMA2, and SMA4 all differ by 1-2km/s. Outflow activity from SMA1, SMA2, SMA4, and SMA6 is observed in several molecules including SiO(5-4) and IRAC 4.5um emission; 24um emission from SMA4 is also detected. Eleven water maser groups are detected, eight of which coincide with SMA1, SMA2, SMA4, and SMA6, while two others are associated with the Sandell source SM2. We also detect a total of 83 Class I CH_3_OH 44GHz maser spots which likely result from the combined activity of many outflows. Our observations paint the portrait of multiple young hot cores in a protocluster prior to the stage where its members become visible in the near-infrared.
