- ID:
- ivo://CDS.VizieR/J/MNRAS/392/1034
- Title:
- IZJHKL' photometry of NGC 6611
- Short Name:
- J/MNRAS/392/1034
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6611 is the massive young cluster (2-3Myr) that ionizes the Eagle Nebula. We present very deep photometric observations of the central region of NGC 6611 obtained with the Hubble Space Telescope and the following filters: ACS/WFC F775W and F850LP and NIC2 F110W and F160W, loosely equivalent to ground-based IZJH filters. This survey reaches down to I~26mag. We construct the initial mass function (IMF) from ~1.5M_{sun}_ well into the brown dwarf regime (down to ~0.02M_{sun}_). We have detected 30-35 brown dwarf candidates in this sample. The low-mass IMF is combined with a higher-mass IMF constructed from the ground-based catalogue from Oliveira et al. We compare the final IMF with those of well-studied star-forming regions: we find that the IMF of NGC 6611 more closely resembles that of the low-mass star-forming region in Taurus than that of the more massive Orion Nebula Cluster. We conclude that there seems to be no severe environmental effect in the IMF due to the proximity of the massive stars in NGC 6611.
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- ID:
- ivo://CDS.VizieR/J/A+A/448/189
- Title:
- IzJHK photometry of IC4665
- Short Name:
- J/A+A/448/189
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the young (30-100Myr) open cluster IC4665 with the aim to determine the shape of the mass function well into the brown dwarf regime. We photometrically select 691 low-mass and 94 brown dwarf candidate members over an area of 3.82 square degrees centred on the cluster. K-band follow-up photometry and Two-Micron All-Sky Survey (<II/246>) data allow a first filtering of contaminant objects from our catalogues. A second filtering is performed for the brightest stars using proper motion data provided by the Tycho-2 (<I/259>) and UCAC2 (<I/289>) public catalogues. Contamination by the field population for the lowest mass objects is estimated using same latitude control fields. We fit observed surface densities of various cluster populations with King profiles and find a consistent tidal radius of 1.0 degree. The presence of possible mass segregation is discussed. In most respects investigated, IC4665 is similar to other young open clusters of similar age: (1) an estimate of the mass function in the low-mass regime and crossing the hydrogen burning limit results in a power law description with slope -0.6, (2) a fraction of BD to total members between 10-19%, (3) a cusp in the mass function is seen at about the substellar boundary, (4) the best-fit lognormal function to the full mass distribution shows an average member mass of 0.32M_{sun}_ if IC4665 has an age of 50Myr.
- ID:
- ivo://CDS.VizieR/J/A+A/450/147
- Title:
- IzJHKs photometry of Collinder 359
- Short Name:
- J/A+A/450/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first deep, optical, wide-field imaging survey of the young open cluster Collinder 359, complemented by near-infrared follow-up observations. This study is part of a large programme aimed at examining the dependence of the mass function on environment and time. We have surveyed 1.6 square degrees in the cluster, in the I and z filters, with the CFH12K camera on the Canada-France-Hawaii 3.6-m telescope down to completeness and detection limits in both filters of 22.0 and 24.0mag, respectively. Based on their location in the optical (I-z,I) colour-magnitude diagram, we have extracted new cluster member candidates in Collinder 359 spanning 1.3-0.03M_{sun}_, assuming an age of 60Myr and a distance of 450pc for the cluster. We have used the 2MASS database as well as our own near-infrared photometry to examine the membership status of the optically-selected cluster candidates. Comparison of the location of the most massive members in Collinder 359 in a (B-V,V) diagram with theoretical isochrones suggests that Collinder 359 is older than Alpha Per but younger than the Pleiades. We discuss the possible relationship between Collinder 359 and IC 4665 as both clusters harbour similar parameters, including proper motion, distance, and age.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A2
- Title:
- J-band variability of AGN
- Short Name:
- J/A+A/555/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectral energy distribution and its variability are basic tools for understanding the physical processes operating in active galactic nuclei (AGN). In this paper we report the results of a one-year near infra red (NIR) and optical monitoring of a sample of 22 AGN known to be {gamma}-ray emitters, aimed at discovering correlations between optical and {gamma}-ray emission. We observed our objects with the Rapid Eye Mount (REM) telescope in J, H, K, and R bands nearly twice every month during their visibility window and derived light curves and spectral indexes. We also analyzed the {gamma}-ray data from the Fermi {gamma}-ray Space Telescope, making weekly averages.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/98
- Title:
- Jet kinematics of blazars at 43GHz with the VLBA
- Short Name:
- J/ApJ/846/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the parsec-scale jet kinematics from 2007 June to 2013 January of a sample of {gamma}-ray bright blazars monitored roughly monthly with the Very Long Baseline Array at 43GHz. In a total of 1929 images, we measure apparent speeds of 252 emission knots in 21 quasars, 12 BL Lacertae objects (BLLacs), and 3 radio galaxies, ranging from 0.02c to 78c; 21% of the knots are quasi-stationary. Approximately one-third of the moving knots execute non-ballistic motions, with the quasars exhibiting acceleration along the jet within 5pc (projected) of the core, and knots in BLLacs tending to decelerate near the core. Using the apparent speeds of the components and the timescales of variability from their light curves, we derive the physical parameters of 120 superluminal knots, including variability Doppler factors, Lorentz factors, and viewing angles. We estimate the half-opening angle of each jet based on the projected opening angle and scatter of intrinsic viewing angles of knots. We determine characteristic values of the physical parameters for each jet and active galactic nucleus class based on the range of values obtained for individual features. We calculate the intrinsic brightness temperatures of the cores, T_b,int_^core^, at all epochs, finding that the radio galaxies usually maintain equipartition conditions in the cores, while ~30% of T_b,int_^core^ measurements in the quasars and BLLacs deviate from equipartition values by a factor >10. This probably occurs during transient events connected with active states.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A122
- Title:
- JHK and IRAC photometry of Sh2-90 YSOs
- Short Name:
- J/A+A/566/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the star formation activity in the molecular complex associated with the Galactic HII region Sh2-90. We obtain the distribution of the ionized and cold neutral gas using radio-continuum and Herschel observations. We use near-infrared and Spitzer data to investigate the stellar content of the complex. We discuss the evolutionary status of embedded massive young stellar objects (MYSOs) using their spectral energy distribution.
- ID:
- ivo://CDS.VizieR/J/ApJS/141/23
- Title:
- JHK' imaging photometry of Seyfert 1. I.
- Short Name:
- J/ApJS/141/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared JHK' imaging photometry was obtained of 331 AGNs consisting mainly of Seyfert 1 active galactic nuclei (AGNs) and quasars (QSOs). This sample was selected to cover a range of radio emission strength, redshift from z=0 to 1, and absolute B magnitude from M_B_=-29mag to -18mag. Among low-z AGNs with z<0.3, Seyfert 1-1.5 AGNs are distributed over a region from a location typical of "galaxies" to a location typical of "QSOs" in the two-color J-H to H-K' diagram, but Seyfert 1.8-2 AGNs are distributed around the location of "galaxies". Moreover, bright AGNs with respect to absolute B magnitude are distributed near the location of "QSOs," while faint AGNs are near the location of "galaxies". The distribution of such low-z AGNs in this diagram was found to have little dependence on their 6 cm radio flux. The near-infrared colors of the AGNs observed with an aperture of 7 pixels (7.49") are more QSO-like than those observed with larger apertures up to 15 pixels (16.1"). This aperture effect may be explained by contamination from the light of host galaxies within larger apertures. This effect is more prominent for less luminous AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJS/141/31
- Title:
- JHK' imaging photometry of Seyfert 1. II.
- Short Name:
- J/ApJS/141/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of 226 AGNs in the near-infrared J, H, and K' bands are presented along with the analysis of the observations for variability. Our sample consists mainly of Seyfert 1 AGNs and QSOs. About a quarter of the objects in each category are radio loud. The AGNs in the entire sample have the redshifts spanning the range from z=0 to 1, and the absolute magnitudes from M_B_=-29 to -18. All the objects were observed twice, and their variability was measured by differential photometry. A reduction method of differential photometry, optimized to the analysis of extended images, has been developed. The systematic error in variability arising from AGNs of highly extended images is estimated to be less than 0.01mag in each of the J, H, and K' bands. The systematic error arising from the flat-fielding is negligible for most AGNs, although it is more than 0.1mag for some particular cases. The overall average flat-fielding error is 0.03mag for the image pairs. We find that these systematic errors are superseded by statistical errors, and the overall average total systematic and statistical errors amounts to 0.05mag in the measured variability in each band.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/464
- Title:
- JHK lightcurves of red giants in the SMC
- Short Name:
- J/MNRAS/448/464
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Long-term JHK light curves have recently become available for large numbers of the more luminous stars in the Small Magellanic Cloud (SMC). We have used these JHK light curves, along with OGLE (Optical Gravitational Lensing Experiment) V and I light curves, to examine the variability of a sample of luminous red giants in the SMC which show prominent long secondary periods (LSPs). The origin of the LSPs is currently unknown. In oxygen-rich stars, we found that while most broad-band colours (e.g. V- I) get redder when an oxygen-rich star dims during its LSP cycle, the J-K colour barely changes and sometimes becomes bluer. We interpret the J-K colour changes as being due to increasing water vapour absorption during declining light caused by the development of a layer of dense cool gas above the photosphere. This result and previous observations which indicate the development of a chromosphere between minimum to maximum light suggest that the LSP phenomenon is associated with the ejection of matter from the stellar photosphere near the beginning of light decline. We explore the possibility that broad-band light variations from the optical to the near-infrared regions can be explained by either dust absorption by ejected matter or large spots on a rotating stellar surface. However, neither model is capable of explaining the observed light variations in a variety of colour-magnitude diagrams. We conclude that some other mechanism is responsible for the light variations associated with LSPs in red giants.
- ID:
- ivo://CDS.VizieR/J/AJ/116/1816
- Title:
- JHKLMNOPQ photometry in Orion cluster
- Short Name:
- J/AJ/116/1816
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine our previous optical spectroscopic and photometric analysis of 1600 stars located in the Orion Nebula Cluster (ONC) with our own and published near-infrared photometric surveys of the region in order to investigate the evidence for and properties of circumstellar disks. We use the near-infrared continuum excess as our primary disk diagnostic, although we also study sources with Ca II triplet emission and those designated as "proplyds."
