The UKIDSS Galactic Plane Survey (GPS) began in 2005 as a 7 year effort to survey ~1800 square degrees of the northern Galactic plane in the J, H, and K passbands. The survey included a second epoch of K band data, with a baseline of 2 to 8 years, fo
r the purpose of investigating variability and measuring proper motions. We have calculated proper motions for 167 Million sources in a 900 square degree area located at l > 60 degrees in order to search for new high proper motion objects. Visual inspection has verified 617 high proper motion sources (> 200 mas/yr) down to K=17, of which 153 are new discoveries. Among these we have a new spectroscopically confirmed T5 dwarf, an additional T dwarf with estimated type T6, 13 new L dwarf candidates, and two new common proper motion systems containing ultracool dwarf candidates. We provide improved proper motions for an additional 12 high proper motion stars that were independently discovered in the WISE dataset during the course of this investigation.
We present initial results of the first panoramic search for high-amplitude near-infrared variability in the Galactic Plane. We analyse the widely separated two-epoch K-band photometry in the 5th and 7th data releases of the UKIDSS Galactic Plane Sur
vey. We find 45 stars with Delta K > 1 mag, including 2 previously known OH/IR stars and a Nova. Even though the mid-plane is not yet included in the dataset, we find the majority (66%) of our sample to be within known star forming regions (SFRs), with two large concentrations in the Serpens OB2 association (11 stars) and the Cygnus-X complex (12 stars). Sources in SFRs show spectral energy distributions (SEDs) that support classification as Young Stellar Objects (YSOs). This indicates that YSOs dominate the Galactic population of high amplitude infrared variable stars at low luminosities and therefore likely dominate the total high amplitude population. Spectroscopic follow up of the DR5 sample shows at least four stars with clear characteristics of eruptive pre-main-sequence variables, two of which are deeply embedded. Our results support the recent concept of eruptive variability comprising a continuum of outburst events with different timescales and luminosities, but triggered by a similar physical mechanism involving unsteady accretion. Also, we find what appears to be one of the most variable classical Be stars.
We report the discovery of a peculiar L dwarf from the UKIDSS LAS, ULAS J222711-004547. The very red infrared photometry (MKO J-K = 2.79$pm$0.06, WISE W1-W2 = 0.65$pm$0.05) of ULAS J222711-004547 makes it one of the reddest brown dwarfs discovered so
far. We obtained a moderate resolution spectrum of this target, and classify it as L7pec, confirming its very red nature. Comparison to theoretical models suggests that the object could be a low-gravity L dwarf with a solar or higher than solar metallicity. Nonetheless, the match of such fits to the spectrum is rather poor and this and other peculiar red L dwarfs pose new challenges for the modeling of ultracool atmospheres. We determined the proper motion of ULAS J222711-004547 using the data available in the literature, and we find that its kinematics do not suggest membership of any of the known young associations. We show that applying a simple de-reddening curve to its spectrum allows it to resemble the spectra of the L7 spectroscopic standards. Given the negligible interstellar reddening of the field containing our target, we conclude that the reddening of the spectrum is mostly due to an excess of dust in the photosphere of the target. De-reddening the spectrum using extinction curves for different dust species gives surprisingly good results and suggests a characteristic grain size of $sim$0.5 $mu$m. We show that by increasing the optical depth, the same extinction curves allow the spectrum of ULAS J222711-004547 to resemble the spectra of unusually blue L dwarfs and slightly metal-poor L dwarfs. Grains of similar size yield very good fits when de-reddening other unusually red L dwarfs in the L5 to L7.5 range. These results suggest that the diversity in near infrared colours and spectra seen in late-L dwarfs could be due to differences in the optical thickness of the dust cloud deck.
The UKIDSS Large Area Survey (LAS) began in 2005, with the start of the UKIDSS program as a 7 year effort to survey roughly 4000 deg$^2$ at high galactic latitudes in Y, J, H and K bands. The survey also included a significant quantity of 2-epoch J b
and observations, with an epoch baseline greater than 2 years to calculate proper motions. We present a near infrared proper motion catalogue for the 1500 deg$^2$ of the 2 epoch LAS data, which includes 135,625 stellar sources and a further 88,324 with ambiguous morphological classifications, all with motions detected above the 5$sigma$ level. We developed a custom proper motion pipeline which we describe here. Our catalogue agrees well with the proper motion data supplied for a 300 deg$^2$ subset in the current WFCAM Science Archive (WSA) tenth data release (DR10) catalogue, and in various optical catalogues, but it benefits from a larger matching radius and hence a larger upper proper motion detection limit. We provide absolute proper motions, using LAS galaxies for the relative to absolute correction. By using local 2nd order polynomial transformations, as opposed to linear transformations in the WSA, we correct better for any local distortions in the focal plane, not including the radial distortion that is removed by the UKIDSS pipeline. We present the results of proper motion searches for new brown dwarfs and white dwarfs. We discuss 41 sources in the WSA DR10 overlap with our catalogue with proper motions $>$300 $mas yr^{-1}$, several of which are new detections. We present 15 new candidate ultra-cool dwarf binary systems.
Vista Variables in the Via Lactea (VVV) is an ESO Public Survey that is performing a variability survey of the Galactic bulge and part of the inner disk using ESOs Visible and Infrared Survey Telescope for Astronomy (VISTA). The survey covers 520 deg
^2 of sky area in the ZYJHK_S filters, for a total observing time of 1929 hours, including ~ 10^9 point sources and an estimated ~ 10^6 variable stars. Here we describe the current status of the VVV Survey, in addition to a variety of new results based on VVV data, including light curves for variable stars, newly discovered globular clusters, open clusters, and associations. A set of reddening-free indices based on the ZYJHK_S system is also introduced. Finally, we provide an overview of the VVV Templates Project, whose main goal is to derive well-defined light curve templates in the near-IR, for the automated classification of VVV light curves.
We report the discovery of 47 new T dwarfs in the Fourth Data Release (DR4) from the Large Area Survey (LAS) of the UKIRT Infrared Deep Sky Survey with spectral types ranging from T0 to T8.5. These bring the total sample of LAS T dwarfs to 80 as of D
R4. In assigning spectral types to our objects we have identified 8 new spectrally peculiar objects, and divide 7 of them into two classes. H2O-H-early have a H2O-H index that differs with the H2O-J index by at least 2 sub-types. CH4-J-early have a CH4-J index that disagrees with the H20-J index by at least 2 subtypes. We have ruled out binarity as a sole explanation for both types of peculiarity, and suggest that they may represent hitherto unrecognised tracers of composition and/or gravity. Clear trends in z(AB)-J and Y-J are apparent for our sample, consistent with weakening absorption in the red wing of the KI line at 0.77microns with decreasing effective temperature. We have used our sample to estimate space densities for T6-T9 dwarfs. By comparing our sample to Monte-Carlo simulations of field T dwarfs for various mass functions of the form phi(M) propto M^-alpha, we have placed weak constraints on the form of the field mass function. Our analysis suggests that the substellar mass function is declining at lower masses, with negative values of alpha preferred. This is at odds with results for young clusters that have been generally found to have alpha > 0.
We describe the public ESO near-IR variability survey (VVV) scanning the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. The survey will take 1929 hours of observations with the 4-metre VISTA telescope
during five years (2010-2014), covering ~10^9 point sources across an area of 520 deg^2, including 33 known globular clusters and ~350 open clusters. The final product will be a deep near-IR atlas in five passbands (0.9-2.5 microns) and a catalogue of more than 10^6 variable point sources. Unlike single-epoch surveys that, in most cases, only produce 2-D maps, the VVV variable star survey will enable the construction of a 3-D map of the surveyed region using well-understood distance indicators such as RR Lyrae stars, and Cepheids. It will yield important information on the ages of the populations. The observations will be combined with data from MACHO, OGLE, EROS, VST, Spitzer, HST, Chandra, INTEGRAL, WISE, Fermi LAT, XMM-Newton, GAIA and ALMA for a complete understanding of the variable sources in the inner Milky Way. This public survey will provide data available to the whole community and therefore will enable further studies of the history of the Milky Way, its globular cluster evolution, and the population census of the Galactic Bulge and center, as well as the investigations of the star forming regions in the disk. The combined variable star catalogues will have important implications for theoretical investigations of pulsation properties of stars.
We present near-infrared long slit and multi-slit spectra of low mass brown dwarf candidates in the Orion Nebula Cluster. The long slit data were observed in the H- & K-bands using NIRI on the Gemini North Telescope. The multi-object spectroscopic ob
servations were made using IRIS2 on the Anglo Australian Telescope at H-band. We develop a spectral typing scheme based on optically calibrated, near infrared spectra of young sources in the Taurus and IC 348 star forming regions with spectral types M3.0 to M9.5. We apply our spectral typing scheme to 52 sources, including previously published UKIRT and GNIRS spectra. 40 objects show strong water absorption with spectral types of M3 to >M9.5. The latest type objects are provisionally classified as early L types. We plot our sources on H-R diagrams overlaid with theoretical pre-main-sequence isochrones. The majority of our objects lie close to or above the 1 Myr isochrone, leading to an average cluster age that is <1 Myr. We find 38 sources lie at or below the hydrogen burning limit (0.075 Msun). 10 sources potentially have masses below the deuterium burning limit (0.012 Msun). We use a Monte Carlo approach to model the observed luminosity function with a variety of cluster age and mass distributions. The lowest chi^2 values are produced by an age distribution centred at 1 Myr, with a mass function that declines at sub-stellar masses according to an M^alpha power law in the range alpha=0.3 to 0.6. We find that truncating the mass function at 0.012 Msun produces luminosity functions that are starved of the faintest magnitudes, even when using bimodal age populations that contain 10 Myr old sources. The results of these Monte Carlo simulations therefore support the existence of a planetary mass population in the ONC.
The UKIDSS Galactic Plane Survey (GPS) is one of the five near infrared Public Legacy Surveys that are being undertaken by the UKIDSS consortium, using the Wide Field Camera on the United Kingdom Infrared Telescope. It is surveying 1868 sq.deg. of th
e northern and equatorial Galactic plane at Galactic latitudes -5<b<5 in the J, H and K filters and a ~200 sq.deg. area of the Taurus-Auriga-Perseus molecular cloud complex in these three filters and the 2.12 um (1-0) H_2 filter. It will provide data on ~2 billion sources. Here we describe the properties of the dataset and provide a users guide for its exploitation. We also present brief Demonstration Science results from DR2 and from the Science Verification programme. These results illustrate how GPS data will frequently be combined with data taken in other wavebands to produce scientific results. The Demonstration Science includes studies of: (i) the star formation region G28.983-0.603, cross matching with Spitzer-GLIMPSE data to identify YSOs; (ii) the M17 nebula; (iii) H_2 emission in the rho Ophiuchi dark cloud; (iv) X-ray sources in the Galactic Centre; (v) external galaxies in the Zone of Avoidance; (vi) IPHAS-GPS optical-infrared spectrophotometric typing. (abridged).
The results of a near-infrared (J H K LP) imaging linear polarimetry survey of 20 young stellar objects (YSOs) in rho Ophiuchi are presented. The majority of the sources are unresolved, with K-band polarizations, P_K < 6 per cent. Several objects are
associated with extended reflection nebulae. These objects have centrosymmetric vector patterns with polarization discs over their cores; maximum polarizations of P_K > 20 per cent are seen over their envelopes. Correlations are observed between the degree of core polarization and the evolutionary status inferred from the spectral energy distribution. K-band core polarizations >6 per cent are only observed in Class I YSOs. A 3D Monte Carlo model with oblate grains aligned with a magnetic field is used to investigate the flux distributions and polarization structures of three of the rho Oph YSOs with extended nebulae. A rho proportional to r^(-1.5) power law for the density is applied throughout the envelopes. The large-scale centrosymmetric polarization structures are due to scattering. However, the polarization structure in the bright core of the nebula appears to require dichroic extinction by aligned non-spherical dust grains. The position angle indicates a toroidal magnetic field in the inner part of the envelope. Since the measured polarizations attributed to dichroic extinction are usually <10 per cent, the grains must either be nearly spherical or very weakly aligned. The higher polarizations observed in the outer parts of the reflection nebulae require that the dust grains responsible for scattering have maximum grain sizes <=1.05 microns.
