- ID:
- ivo://CDS.VizieR/J/A+A/645/A116
- Title:
- NGC 2808, NGC 6266 and NGC 6397 Gaia DR2 sources
- Short Name:
- J/A+A/645/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extratidal stars are stellar bodies that end up outside the tidal radius of a cluster as a result of internal processes or external forces acting upon it. The presence and spatial distribution of these stars can give us insights into the past evolution of a cluster inside our Galaxy. Previous works suggest that globular clusters, when explored in detail, show evidence of extratidal stars. We aim to search for possible extratidal stars in the Galactic globular clusters NGC 6397, NGC 2808, and NGC 6266 using the photometry and proper motion measurements from Gaia DR2 database. The extratidal stars for the clusters were selected on the basis of: their distance from the cluster center, similarity in their proper motions to the cluster population, and their position on the color-magnitude diagram of the clusters. Each cluster was explored in an annulus disk from the tidal radius up to five times the tidal radii. The significance level of the number of selected extratidal stars was determined on the basis of the distribution of Milky Way stars according to the Besancon Galaxy model and Gaia data. To understand the observed extratidal features, the orbits of the clusters were also determined using GravPot16. Finally, 120, 126, and 107 extratidal candidate stars were found lying outside the tidal radius of the globular clusters NGC 6397, NGC 2808, and NGC 6266, respectively. 70%, 25.4%, and 72.9% of the extratidal stars found are located outside the Jacobi radius of NGC 6397, NGC 2808, and NGC 6266, respectively. The spatial distribution of the extratidal stars belonging to NGC 6397 appears S-like, extending along the curved leading and trailing arms. NGC 2808 has an overdensity of stars in the trailing part of the cluster and NGC 6266 seems to have overdensities of extratidal stars in its eastern and northern sides. Proper motions and color-magnitude diagrams can be used to identify extratidal candidate stars around GCs. Nonetheless, depending on how different the kinematics and stellar populations of a cluster are compared to the Milky Way field, the fraction of contamination can be larger. All three clusters are found to have extratidal stars outside their tidal radii. For NGC 6397 and NGC 2808, these stars may be the result of a combined effect of the disc shocks and tidal disruptions. For NGC 6266, the distribution of extratidal stars is symmetrical around it, most likely indicating that the cluster has an extended stellar envelope.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/131/239
- Title:
- NGC 1750 + NGC 1758 BVR photometry
- Short Name:
- J/A+AS/131/239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photographic astrometric and photometric catalogue. Table 6 contains (x,y) positions, (mu_x, mu_y) relative proper motions and BVR photographic photometry. Notes give cross-identifications with other catalogues. Table 11 contains equatorial positions (alpha, delta) and absolute proper motions (mu_alpha cos delta, mu_delta) in FK5 and ICRS reference systems.
- ID:
- ivo://CDS.VizieR/J/AJ/115/130
- Title:
- NGC 925 & NGC 1637 supergiants VRI CCD photometry
- Short Name:
- J/AJ/115/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- V, R, and I CCD images obtained with the Canada-France-Hawaii Telescope are used to investigate the bright stellar content of the barred spiral galaxies NGC 925 and NGC 1637. Not counting objects located in H II regions, we detect 295 supergiants in NGC 925 and 266 in NGC 1637. Comparisons with theoretical isochrones indicate that massive star formation in NGC 925 has been ongoing for at least a few tens of millions of years. Most of the supergiants in NGC 925 are younger than 20Myr and have masses between 10 and 60M_{sun}_. The majority of supergiants in NGC 1637 appear to be younger than 40Myr and have initial masses between 8 and 60 M_{sun}_. The luminosity functions of supergiants in both galaxies follow power laws with exponents d(logn)/d(logV)=0.50+/-0.05 for NGC 925 and 0.62+/-0.04 for NGC 1637. These values are shallower than what is seen in most spiral galaxies, although there are some exceptions. Archival Hubble Space Telescope images of NGC 925 are used to assess the effects of blending on our photometric measurements. We conclude that crowding could cause a flattening of the luminosity function and bias the brightnesses of the most luminous stars. The brightest red supergiants are used to estimate the distance moduli of these galaxies. After applying corrections for blending, we find that {mu}_0_=29.67 for NGC 925 and {mu}_0_=29.47 for NGC 1637, corresponding to linear distances of 8.6^+1.1^_-1.0_ and 7.8^+1.0^_-0.9_Mpc, respectively. The distance computed for NGC 925 is in good agreement with that recently derived from Cepheids.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A77
- Title:
- NGC 1893 optical and NIR photometry
- Short Name:
- J/A+A/527/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Different environmental conditions can play a crucial role in determining final products of the star formation process and in this context, less favorable activities of star formation are expected in the external regions of our Galaxy. We studied the properties of the young open cluster NGC 1893 located about 12kpc from the galactic center, to investigate how different physical conditions can affect the process of star formation. By adopting a multiwavelength approach, we compiled a catalog extending from X-rays to NIR data to derive the cluster membership. In addition, optical and NIR photometric properties are used to evaluate the cluster parameters. We find 415 diskless candidate members plus 1061 young stellar objects with a circumstellar disk or class II candidate members, 125 of which are also H{alpha} emitters. Considering the diskless candidate members, we find that the cluster distance is 3.6+/-0.2kpc and the mean interstellar reddening is E(B-V)=0.6+/-0.1 with evidence of differential reddening in the whole surveyed region. NGC 1893 contains a conspicuous population of pre-main sequence stars together with the well studied main sequence cluster population; we found a disk fraction of about 70% similar to that found in clusters of similar age in the solar neighbor and then, despite expected unfavorable conditions for star formation, we conclude that very rich young clusters can form also in the outer regions of our Galaxy.
2375. NGC 3516 optical flare
- ID:
- ivo://CDS.VizieR/J/A+A/638/A13
- Title:
- NGC 3516 optical flare
- Short Name:
- J/A+A/638/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations from the short-term intensive optical campaign (from September 2019 to January 2020) of the changing-look Seyfert NGC 3516. This active galactic nucleus is known to have strong optical variability and has changed its type in the past. It has been in the low-activity state in the optical since 2013, with some rebrightening from the end of 2015 to the beginning of 2016, after which it remained dormant. We aim to study the photometric and spectral variability of NGC 3516 from the new observations in U- and B-bands and examine the profiles of the optical broad emission lines in order to demonstrate that this object may be entering a new state of activity. NGC 3516 has been monitored intensively for the past 4 months with an automated telescope in U and B filters, enabling accurate photometry of 0.01 precision. Spectral observations were triggered when an increase in brightness was spotted. We support our analysis of past-episodes of violent variability with the UV and X-ray long-term light curves constructed from the archival Swift/UVOT and Swift/XRT data. An increase of the photometric magnitude is seen in both U and B filters to a maximum amplitude of 0.25mag and 0.11mag, respectively. During the flare, we observe stronger forbidden high-ionization iron lines ([FeVII] and [FeX]) than reported before, as well as the complex broad H{alpha} and H{beta} lines. This is especially seen in H{alpha}, which appears to be double-peaked. It seems that a very broad component of ~10000km/s in width in the Balmer lines is appearing. The trends in the optical, UV, and X-ray light curves are similar, with the amplitudes of variability being significantly larger in the case of UV and X-ray bands. The increase of the continuum emission, the variability of the coronal lines, and the very broad component in the Balmer lines may indicate that the AGN of NGC 3516 is finally leaving the low-activity state in which it has been for the last ~3 years.
- ID:
- ivo://CDS.VizieR/J/MNRAS/476/2813
- Title:
- NGC 2282 photometry of variable stars
- Short Name:
- J/MNRAS/476/2813
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report here CCD I-band time series photometry of a young (2-5Myr) cluster NGC 2282, in order to identify and understand the variability of pre-main-sequence (PMS) stars. The I-band photometry, down to ~20.5mag, enables us to probe the variability towards the lower mass end (~0.1M_{sun}_) of PMS stars. From the light curves of 1627 stars, we identified 62 new photometric variable candidates. Their association with the region was established from H{alpha} emission and infrared (IR) excess. Among 62 variables, 30 young variables exhibit H{alpha} emission, near-IR (NIR)/mid-IR (MIR) excess or both and are candidate members of the cluster. Out of 62 variables, 41 are periodic variables, with a rotation rate ranging from 0.2-7d. The period distribution exhibits a median period at ~1d, as in many young clusters (e.g. NGC 2264, ONC, etc.), but it follows a unimodal distribution, unlike others that have bimodality, with slow rotators peaking at ~6-8d. To investigate the rotation-disc and variability-disc connection, we derived the NIR excess from {Delta}(I-K) and the MIR excess from Spitzer [3.6]-[4.5]um data. No conclusive evidence of slow rotation with the presence of discs around stars and fast rotation for discless stars is obtained from our periodic variables. A clear increasing trend of the variability amplitude with IR excess is found for all variables.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A147
- Title:
- NGC 2070 point sources radial velocities
- Short Name:
- J/A+A/614/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce VLT-MUSE observations of the central 2'x2' (30x30pc) of the Tarantula Nebula in the Large Magellanic Cloud. The observations provide an unprecedented spectroscopic census of the massive stars and ionised gas in the vicinity of R136, the young, dense star cluster located in NGC 2070, at the heart of the richest star-forming region in the Local Group. Spectrophotometry and radial-velocity estimates of the nebular gas (superimposed on the stellar spectra) are provided for 2255 point sources extracted from the MUSE datacubes, and we present estimates of stellar radial velocities for 270 early-type stars (finding an average systemic velocity of 271+/-41km/s). We present an extinction map constructed from the nebular Balmer lines, with electron densities and temperatures estimated from intensity ratios of the [SII], [NII], and [SIII] lines. The interstellar medium, as traced by H{alpha} and [NII] {lambda}6583, provides new insights in regions where stars are probably forming. The gas kinematics are complex, but with a clear bi-modal, blue- and red-shifted distribution compared to the systemic velocity of the gas centred on R136. Interesting point-like sources are also seen in the eastern cavity, western shell, and around R136; these might be related to phenomena such as runaway stars, jets, formation of new stars, or the interaction of the gas with the population of Wolf-Rayet stars. Closer inspection of the core reveals red-shifted material surrounding the strongest X-ray sources, although we are unable to investigate the kinematics in detail as the stars are spatially unresolved in the MUSE data. Further papers in this series will discuss the detailed stellar content of NGC 2070 and its integrated stellar and nebular properties.
2378. NGC 7538 region YSOs
- ID:
- ivo://CDS.VizieR/J/MNRAS/467/2943
- Title:
- NGC 7538 region YSOs
- Short Name:
- J/MNRAS/467/2943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep optical photometric data on the NGC 7538 region were collected and combined with archival data sets from the Chandra, 2MASS and Spitzer surveys to generate a new catalogue of young stellar objects (YSOs) including those not showing infrared excess emission. This new catalogue is complete down to 0.8M_{sun}_. The nature of the YSOs associated with the NGC 7538 region and their spatial distribution are used to study the star-formation process and the resultant mass function (MF) in the region. Out of the 419 YSOs, ~91 per cent have ages between 0.1 and 2.5Myr and ~86 per cent have masses between 0.5 and 3.5M_{sun}_, as derived by the spectral energy distribution fitting analysis. Around 24, 62 and 2 per cent of these YSOs are classified to be class I, class II and class III sources, respectively. The X-ray activities for the class I, class II and class III objects are not significantly different from each other. This result implies that the enhanced X-ray surface flux due to the increase in the rotation rate may be compensated for by the decrease in the stellar surface area during the pre-main-sequence evolution. Our analysis shows that the O3V type high-mass star IRS 6 may have triggered the formation of young low-mass stars up to a radial distance of 3pc. The MF shows a turn-off at around 1.5M_{sun}_ and the value of its slope {Gamma} in the mass range 1.5<M/M_{sun}_<6 is -1.76+/-0.24, which is steeper than the Salpeter value.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/2438
- Title:
- NGC 1960 (RI)c photometric catalogue
- Short Name:
- J/MNRAS/434/2438
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep Cousins RI photometric survey of the open cluster NGC 1960, complete to R_C_=~22, I_C_=~21, that is used to select a sample of very low mass cluster candidates. Gemini spectroscopy of a subset of these is used to confirm membership and locate the age-dependent 'lithium depletion boundary' (LDB) - the luminosity at which lithium remains unburned in its low-mass stars. The LDB implies a cluster age of 22+/-4Myr and is quite insensitive to choice of evolutionary model. NGC 1960 is the youngest cluster for which a LDB age has been estimated and possesses a well-populated upper main sequence and a rich low-mass pre-main sequence. The LDB age determined here agrees well with precise age estimates made for the same cluster based on isochrone fits to its high- and low-mass populations. The concordance between these three age estimation techniques, that rely on different facets of stellar astrophysics at very different masses, is an important step towards calibrating the absolute ages of young open clusters and lends confidence to ages determined using any one of them.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A104
- Title:
- NGC3278, SN2009bb host, ATCA and MUSE data
- Short Name:
- J/A+A/618/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The host galaxies of gamma-ray bursts (GRBs) have been claimed to have experienced a recent inflow of gas from the intergalactic medium. This is because their atomic gas distribution is not centred on their optical emission and because they are deficient in molecular gas given their high star-formation rates. Similar studies have not been conducted for host galaxies of relativistic supernovae (SNe), which may have similar progenitors. The potential similarity of the powering mechanisms of relativistic SNe and GRBs allowed us to make a prediction that relativistic SNe are born in environments similar to those of GRBs, i.e. rich in atomic gas. Here we embark on testing this hypothesis by analysing the properties of the host galaxy NGC 3278 of the relativistic SN 2009bb. This is the first time the atomic gas properties of a relativistic SN host is analysed and the first time resolved 21cm hydrogen line (HI) information is provided for a host of a SN of any type. We obtained radio observations with Australia Telescope Compact Array (ATCA) covering HI line; and optical integral field unit spectroscopy observations with Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT). Moreover, we analysed archival carbon monoxide (CO) and broad-band data for this galaxy. The atomic gas distribution of NGC3278 is not centred on the optical galaxy centre, but instead around a third of atomic gas resides in the region close to the SN position. This galaxy has a few times lower atomic and molecular gas masses than predicted from its star formation rate (SFR). Its specific star formation rate (sSFR=SFR/M*) is ~2-3 times higher than the main-sequence value, placing it at the higher end of the main sequence towards starburst galaxies. SN 2009bb exploded close to the region with the highest SFR density and the lowest age, as evident from high Halpha EW, corresponding to the age of the stellar population of ~5.5Myr. Assuming this timescale was the lifetime of the progenitor star, its initial mass would have been close to ~36M_{sun}_. As for GRB hosts, the gas properties of NGC3278 are consistent with a recent inflow of gas from the intergalactic medium, which explains the concentration of atomic gas close to the SN position and the enhanced SFR. Super-solar metallicity at the position of the SN (unlike for most of GRBs) may mean that relativistic explosions signal a recent inflow of gas (and subsequent star-formation), and their type (GRBs or SNe) is determined by either i) the metallicity of the inflowing gas (metal-poor gas results in a GRB explosion and metal-rich gas in a relativistic SN explosion without an accompanying GRB), or ii) by the efficiency of gas mixing (efficient mixing for SN hosts leading to quick disappearance of metal-poor regions), or iii) by the type of the galaxy (more metal-rich galaxies would result in only a small fraction of star-formation to be fuelled by metal-poor gas).
