In this paper we continue our investigation on the isophotal nature, accuracy, and uniformity of the magnitude system adopted in the Southern Sky Redshift Survey extension (SSRS2). Extending our earlier work, we examine galaxies in the equatorial region, primarily in the declination range -17.5 deg <= Dec. <= 0 deg, over a large range of right ascension, covering the southern and northern Galactic caps. For this purpose, we have obtained CCD isophotal magnitudes in the B and R bands for 265 galaxies of different morphological types. Using this larger sample we confirm our earlier claim that the m(SSRS2) magnitudes are very nearly the magnitude measured within the isophote mu_B = 26 mag/arcsec^2, with a dispersion of about 0.30 mag. The relative zero-point offset between our m(SSRS2) magnitudes and CCD photometry is -0.02 mag from all data we have obtained. However, we detect a variation of the zero-point across different regions of the sky of +/- 0.10 mag for regions at large angular separations. We also estimate that the zero-point offset between the m(SSRS2) and Zwicky systems is relatively small (~0.10 mag), which should allow us to combine the data from the SSRS2 and the CfA2 Redshift Survey.
We analyse a manuscript star catalogue by Wilhem IV, Landgraf von Hessen-Kassel from 1586. From measurements of altitudes and of angles between stars, given in the catalogue, we find that the measurement accuracy averages 26 arcsec for eight fundamental stars, compared to 49 arcsec of the measurements by Brahe. The computation in converting altitudes to declinations and angles between stars to celestial position is very accurate, with errors negligible with respect to the measurement errors. Due to an offset in the position of the vernal equinox the positional error of the catalogue is slightly worse than that of Brahe's catalogue, but when correction is made for the offset -- which was known to 17th century astronomers -- the catalogue is more accurate than that of Brahe. We provide machine-readable Tables of the catalogue.
We present the first ever global, spatially resolved reconstruction of the star formation history (SFH) of the Large Magellanic Cloud (LMC), based on the application of our StarFISH analysis software to the multiband photometry of 20 million of its stars from the Magellanic Clouds Photometric Survey (MCPS). The general outlines of our results are consistent with previously published results: following an initial burst of star formation, there was a quiescent epoch from approximately 12 to 5Gyr ago. Star formation then resumed and has proceeded until the current time at an average rate of roughly 0.2M_{sun}_/yr, with temporal variations at the factor of 2 level.
Since its appearance in 1966, the SAO Catalogue (SAO, 1966) has been the primary source for stellar positions and proper motions. Typical values for the rms errors are 1 arcsec in the positions at epoch 1990, and 1.5 arcsec/century in the proper motions. The corresponding figures for the AGK3 (Heckmann et al., 1975) on the northern hemisphere are 0.45 arcsec and 0.9 arcsec/century. Common to both catalogues is the fact that proper motions area derived from two observational epochs only. Both catalogues are nominally on the B1950/FK4 coordinate system. The PPM Star Catalogue (Roeser and Bastian, 1991, Bastian et al., 1993; for a short description see Roeser and Bastian, 1993) effectively replaced these catalogues by providing more precise astrometric data for more stars on the J2000/FK5 coordinate system. Compared to the SAO Catalogue the improvement in precision is about a factor of 3 on the northern and a factor of 6 to 10 on the southern hemisphere. In addition, the number of stars is increased by about 50 percent. Typical values for the rms errors on the northern hemisphere are 0.27 arcsec in the positions at epoch 1990, and 0.42 arcsec/century in the proper motions. On the southern hemisphere PPM is much better, the corresponding figures being 0.11 arcsec and 0.30 arcsec/century. The improvement over the SAO Catalogue was made possible by the advent of new big catalogues of position measurements and by the inclusion of the century-old Astrographic Catalogue (AC) into the derivation of proper motions (for a description of AC see Eichhorn, 1974). But even PPM does not fully exploit the treasure of photographic position measurements available in the astronomical literature of the last 100 years. The Astrographic Catalogue contains roughly four million stars that are not included in PPM. For most of them no precise modern-epoch position measurements exist. Thus it is not yet possible to derive proper motions with PPM quality for all AC stars. But among the 4 million there is a subset of some 100,000 CPC-2 stars that are not included in PPM. These stars constitute the 90,000 Stars Supplement to PPM. See file "desc.txt" for complete explanations provided by the authors.
With an apparent cluster diameter of 1.5deg and an age of ~4Myr, Trumpler 37 is an ideal target for photometric monitoring of young stars as well as for the search of planetary transits, eclipsing binaries and other sources of variability. The YETI consortium has monitored Trumpler 37 throughout 2010 and 2011 to obtain a comprehensive view of variable phenomena in this region. In this first paper we present the cluster properties and membership determination as derived from an extensive investigation of the literature. We also compared the coordinate list to some YETI images. For 1872 stars we found literature data. Among them 774 have high probability of being member and 125 a medium probability. Based on infrared data we re-calculate a cluster extinction of 0.9-1.2mag. We can confirm the age and distance to be 3-5Myr and ~870pc. Stellar masses are determined from theoretical models and the mass function is fitted with a power-law index of {alpha}=1.90 (0.1-0.4M_{sun}_) and {alpha}=1.12 (1-10M_{sun}_).
The high-precision astrometry from the second data release of the Gaia mission (Cat. I/345) has made it possible to greatly improve the census of members of nearby clusters and associations. I have applied the Gaia data to the Taurus star-forming region, refining the sample of known members and identifying candidates for undiscovered members. The resulting samples of members and candidates provide the best constraints to date on the distribution of ages and the initial mass function (IMF) in Taurus. Several studies over the last 30 years have proposed the existence of a population of older stars (>~10 Myr) that is associated with the Taurus clouds. The data from Gaia demonstrate that such a population does not exist. Meanwhile, previous IMF estimates for small fields surrounding the Taurus aggregates have exhibited a surplus of K7-M0 stars (0.7-0.8 M_{sun}_) relative to star-forming clusters such as IC 348 and the Orion Nebula Cluster. However, that difference disappears when the new census of the entire region is considered, which should be complete for spectral types earlier than M6-M7 at A_J_<1. Thus, there is little variation in the stellar IMF across the 3-4 orders of magnitude in stellar density that are present in nearby star-forming regions. Finally, I note that the proper motions of two previously known members, KPNO 15 and 2MASS J04355209+2255039, indicate that they may have been ejected from the same location within the L1536 cloud ~7200 years ago.
The Stromlo-APM Redshift Survey consists of 1797 galaxies with b(J)<17.15 selected randomly at a rate of 1 in 20 from Automated Plate Measurement (APM) scans. The survey covers a solid angle of 1.3sr (4300 square degrees) in the south galactic cap. Redshifts have been measured for 1790 (99.6%) of the galaxies. The median galaxy recession velocity is 15,300 km/s and so the volume probed is approximately V=1.38 million Mpc^3/h^3.
The Swift Small Magellanic Cloud (SMC) Survey, S-CUBED, is a high-cadence shallow X-ray survey of the SMC. The survey consists of 142 tiled pointings covering the optical extent of the SMC, which is performed weekly by NASA's Neil Gehrels Swift Observatory, with an exposure per tile of 60s. The survey is focused on discovery and monitoring of X-ray outbursts from the large known and unknown population of Be/X-ray binaries (BeXRBs) in the SMC. Given the very low background of Swift's X-ray telescope, even with a short exposure per tile, S-CUBED is typically sensitive to outbursts in the SMC at >1%-2% Eddington luminosity for a typical 1.4M_{sun}_ neutron star compact object. This sensitivity, combined with the high cadence and the fact that the survey can be performed all year round, makes it a powerful discovery tool for outbursting accreting X-ray pulsars in the SMC. In this paper we describe results from the first year of observations of S-CUBED, which includes the 1SCUBEDX catalog of 265 X-ray sources, 160 of which are not identified with any previously cataloged X-ray source. We report on bulk properties of sources in the 1SCUBEDX catalog. Finally, we focus on results of S-CUBED observations of several interesting sources, which includes discovery of three Type II outbursts from BeXRBs and the detection of Type I outbursts and orbital periods in six BeXRB systems.
We present the results of 325MHz Giant Metrewave Radio Telescope observations of a supercluster field, known to contain five Abell clusters at redshift z~0.2. We achieve a nominal sensitivity of 34uJy/beam towards the phase centre. We compile a catalogue of 3257 sources with flux densities in the range 183uJy-1.5Jy within the entire ~6.5deg^2^ field of view. Subsequently, we use available survey data at other frequencies to derive the spectral index distribution for a sub-sample of these sources, recovering two distinct populations - a dominant population which exhibit spectral index trends typical of steep-spectrum synchrotron emission, and a smaller population of sources with typically flat or rising spectra. We identify a number of sources with ultrasteep spectra or rising spectra for further analysis, finding two candidate high-redshift radio galaxies and three gigahertz-peaked-spectrum radio sources. Finally, we derive the Euclidean-normalized differential source counts using the catalogue compiled in this work, for sources with flux densities in excess of 223uJy. Our differential source counts are consistent with both previous observations at this frequency and models of the low-frequency source population. These represent the deepest source counts yet derived at 325MHz. Our source counts exhibit the well-known flattening at mJy flux densities, consistent with an emerging population of star-forming galaxies; we also find marginal evidence of a downturn at flux densities below 308uJy, a feature so far only seen at 1.4GHz.
We use a compilation of redshifts of rich clusters by Andernach, Tago and Stengler-Larrea (1996, in preparation) to determine superclusters of rich clusters up to a redshift of z=0.12. Superclusters were searched for with a clustering algorithm, using a neighbourhood radius of 24h^-1^Mpc (h is the Hubble constant in units of 100km/s/Mpc). The catalogue contains 220 superclusters of rich clusters, of which 90 superclusters have been determined for the first time. Table A2 gives the supercluster number, its multiplicity, centre coordinates, a list of member clusters and identifications with the catalogue by Einasto et al. (1994MNRAS.269..301E).
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