-On the basis of near-infrared imaging observations, we derived visual extinction (A V ) distribution toward ten Bok globules through measurements of both the color excess (E H−K ) and the stellar density at J, H, and K s (star count). Radial column density profiles for each globule were analyzed with the Bonnor-Ebert sphere model. Using the data of our ten globules and four globules in the literature, we investigated the stability of globules on the basis of ξ max , which characterizes the Bonnor-Ebert sphere as well as the stability of the equilibrium state against the gravitational collapse. We found that more than half of starless globules are located near the critical state (ξ max = 6.5 ± 2). Thus, we suggest that a nearly critical Bonnor-Ebert sphere characterizes the typical density structure of starless globules. Remaining starless globules show clearly unstable states (ξ max > 10). Since unstable equilibrium states are not long maintained, we expect that these globules are on the way to gravitational collapse or that they are stabilized by non-thermal support. It was also found that all the starforming globules show unstable solutions of ξ max > 10, which is consistent with the fact that they have started gravitational collapse. We investigated the evolution of a collapsing gas sphere whose initial condition is a nearly critical Bonnor-Ebert sphere. We found that the column density profiles of the collapsing sphere mimic those of the static Bonnor-Ebert spheres in unstable equilibrium. The collapsing gas sphere resembles marginally unstable Bonnor-Ebert spheres for a long time. We found that the frequency distribution of ξ max for the observed starless globules is consistent with that from model calculations of the collapsing sphere. In addition to the near-infrared observations, we carried out radio molecular line observations (C 18 O and N 2 H + ) toward the same ten globules. We confirmed that most of the globules are dominated by thermal support. The line width of each globule was used to estimate the cloud temperature including the contribution from turbulence, with which we estimated the distance to the globules from the Bonnor-Ebert model fitting.Subject headings: ISM: clouds -dust, extinction -ISM: globules -stars: formation * Recently, a low luminosity protostar was discovered toward the globule Lynds 1014, which is known to accompany no IRAS point sources, using the Spitzer Space Telescope (Young et al. 2004). Though Spitzer data are useful to clarify whether globules contain protostars or not, Spitzer data is available only for one source, CB 131, among the "IRAS-less" globules in Table 1. We briefly checked mid-infrared data of the Spitzer telescope toward CB 131 and found that there is no protostar candidates near the center of the globule. Though a source is located near the globule †

We have performed a cross-identification between Optical Gravitational Lensing Experiment II (OGLE-II) data and single-epoch Simultaneous three-colour Infrared Imager for Unbiased Surveys (SIRIUS) near-infrared (NIR) JHK survey data in the Large and Small Magellanic Clouds (LMC and SMC, respectively). After eliminating obvious spurious variables, variables with too few good data and variables that seem to have periods longer than the available baseline of the OGLE-II data, we determined the pulsation periods for 8852 and 2927 variables in the LMC and SMC, respectively.Based on these homogeneous data, we studied the pulsation properties and metallicity effects on period-K magnitude (PK) relations by comparing the variable stars in the LMC and SMC. The sample analysed here is much larger than the previous studies, and we found the following new features in the PK diagram. (1) Variable red giants in the SMC form parallel sequences on the PK plane, just like those found by Wood in the LMC. (2) Both sequences A and B of Wood have discontinuities, and they occur at the K-band luminosity of the tip of the red giant branch. (3) The sequence B of Wood separates into three independent sequences B ± and C . (4) A comparison between the theoretical pulsation models and observational data suggests that the variable red giants on sequences C and newly discovered C are pulsating in the fundamental and first overtone modes, respectively. (5) The theory cannot explain the pulsation mode of sequences A ± and B ± , and they are unlikely to be the sequences for the first and second overtone pulsators, as was previously suggested. (6) The zero-points of PK relations of Cepheids in the metal deficient SMC are fainter than those of the LMC by ≈0.1 mag but those of SMC Miras are brighter than those of the LMC by ≈0.13 mag (adopting the distance modulus offset between the LMC and SMC to be 0.49 mag and assuming the slopes of the PK relations are the same in the two galaxies), which are probably due to metallicity effects.

Accepted by MNRAS. 30 pages, 15 figures (some at reduced resolution due to upload restrictions - full res version at http://surveys.roe.ac.uk/wsa/pubs.html)This paper defines the UKIRT Infrared Deep Sky Survey (UKIDSS) Early Data Release (EDR). UKIDSS is a set of five large near-infra-red surveys defined by Lawrence et al. (2006), being undertaken with the UK Infra-red Telescope (UKIRT) Wide Field Camera (WFCAM). The programme began in May 2005 and has an expected duration of seven years. Each survey uses some or all of the broadband filter complement ZYJHK. The EDR is the first public release of data to the European Southern Observatory (ESO) community. All worldwide releases occur after a delay of 18 months from the ESO release. The EDR provides a small sample dataset, ~50 sq.deg (about 1% of the whole of UKIDSS), that is a lower limit to the expected quality of future survey data releases. In addition, an EDR+ dataset contains all EDR data plus extra data of similar quality, but for areas not observed in all of the required filters (amounting to ~220 sq.deg). The first large data release, DR1, will occur in mid-2006. We provide details of the observational implementation, the data reduction, the astrometric and photometric calibration, and the quality control procedures. We summarise the data coverage and quality (seeing, ellipticity, photometricity, depth) for each survey and give a brief guide to accessing the images and catalogues from the WFCAM Science Archive

We present the result of a near-infrared (JHK S ) survey along the Galactic plane, −10. • 5 ≤ l ≤ 10. • 5 and b = +1 • , with the IRSF 1.4m telescope and the SIRIUS camera. K S vs. H − K S color-magnitude diagrams reveal a well-defined population of red clump (RC) stars whose apparent magnitude peak changes continuously along the Galactic plane, from K S = 13.4 at l = −10 • to K S = 12.2 at l = 10 • after dereddening. This variation can be explained by the bar-like structure found in previous studies, but we find an additional inner structure at | l | 4 • , where the longitude -apparent magnitude relation is distinct from the outer bar, and the apparent magnitude peak changes by only ≈ 0.1 mag over the central 8 • . The exact nature of this inner structure is as yet uncertain.

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We present a near-infrared ($JHK_{\rm s}$) photometric catalog, including 14811185 point sources for a 40 deg$^2$ area of the Large Magellanic Cloud, 2769682 sources for an 11 deg$^2$ area of the Small Magellanic Cloud, and 434145 sources for a 4 deg$^2$ area of the Magellanic Bridge. The 10$\sigma$ limiting magnitudes are 18.8, 17.8, and 16.6 mag at $J, H$, and $K_{\rm s}$, respectively. The photometric and astrometric accuracies for bright sources are 0.03–0.04 mag and 0$\rlap {.}{^{\prime\prime}}$1, respectively. Based on the catalog, we also present (1) spatial distributions, (2) luminosity functions, (3) color–color diagrams, and (4) color–magnitude diagrams for point sources toward the Magellanic Clouds.

We present a deep JHK s -band imaging survey of the W3 Main star-forming region, using the near-infrared camera SIRIUS mounted on the University of Hawaii 2.2 m telescope. The near-infrared survey covers an area of $24 arcmin 2 with 10 limiting magnitudes of $19.0, 18.1, and 17.3 in the J, H, and K s bands, respectively. We construct JHK color-color and J versus JÀH and K versus HÀK color-magnitude diagrams to identify young stellar objects and estimate their masses. Based on these color-color and color-magnitude diagrams, a rich population of young stellar objects is identified that is associated with the W3 Main region. A large number of previously unreported red sources (HÀK > 2) have also been detected around W3 Main. We argue that these red stars are most probably pre-main-sequence stars with intrinsic color excesses. We find that the slope of the K s -band luminosity function (KLF) of W3 Main is lower than the typical values reported for young embedded clusters. The derived slope of the KLF is the same as that found in 1996 by Megeath and coworkers, from which analysis indicated that the W3 Main region has an age in the range of 0.3-1 Myr. Based on the comparison between models of pre-main-sequence stars and the observed color-magnitude diagram, we find that the stellar population in W3 Main is primarily composed of low-mass pre-main-sequence stars. We also report the detection of isolated young stars with large infrared excesses that are most probably in their earliest evolutionary phases.

The data of 8852 and 2927 variable stars detected by the OGLE survey in the Large and Small Magellanic Clouds are presented. They are cross‐identified with the SIRIUS JHK survey data, and their infrared properties are discussed. Variable red giants are well separated on the period–(J−K) plane, suggesting that it could be a good tool to distinguish their pulsation mode and type.