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Subaru Telescope (subaru + telescope)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

The first appearance of the red sequence of galaxies in proto-clusters at 2 ,z, 3

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007
Tadayuki Kodama
ABSTRACT We explore the evolved galaxy population in the proto-clusters around four high- z radio galaxies at 2 ,z, 3 based on wide-field near-infrared (NIR) imaging. Three of the four fields are known proto-clusters as demonstrated by overdensities of line-emitting galaxies at the same redshifts as the radio galaxies found by narrow-band surveys and spectroscopic follow-up observations. We imaged the fields of three targets (PKS 1138,262, USS 0943,242 and MRC 0316,257) to a depth of Ks, 22 (Vega magnitude, 5,) over a 4 × 7 arcmin2 area centred on the radio galaxies with a new wide-field NIR camera, Multi-Object Infra-Red Camera and Spectrograph (MOIRCS), on the Subaru Telescope. Another target (USS 1558,003) was observed with Son of ISAAC on the New technology Telescope (NTT) to a depth of Ks= 20.5 (5,) over a 5 × 5 arcmin2 area. We apply colour cuts in J,Ks and/or JHKs in order to exclusively search for galaxies located at high redshifts: z > 2. To the 5, limiting magnitudes, we see a significant excess of NIR-selected galaxies by a factor of 2 to 3 compared to those found in the field of GOODS-South. The spatial distribution of these NIR-selected galaxies is not uniform and traces structures similar to those of emission-line galaxies, although the samples of NIR-selected galaxies and emitters show little overlap, from which we conclude that the former tend to be an evolved population with much higher stellar mass than the latter, young and active emitters. We focus on the NIR colour,magnitude sequence of the evolved population and find that the bright-end (Mstars > 1011 M,) of the red sequence is well populated by z, 2 but much less so in the z, 3 proto-clusters. This may imply that the bright-end of the colour,magnitude sequence first appeared between z= 3 and 2, an era coinciding with the appearance of sub-mm galaxies and the peak of the cosmic star formation rate. Our observations show that during the same epoch, massive galaxies are forming in high-density environments by vigorous star formation and assembly. [source]

A Subaru/Suprime-Cam wide-field survey of globular cluster populations around M87 , II.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2006
Colour, spatial distribution
ABSTRACT We have performed a wide-field imaging survey of the globular cluster (GC) populations around M87 with Suprime-Cam on the 8.2-m Subaru Telescope. A field extending from the centre of M87 out to a radius of ,0.5 Mpc was observed through the BVI filters. By investigating the GC colour distribution as a function of distance from M87 and NGC 4552, another luminous Virgo elliptical in our survey field, it is found that clear bimodality [(V,I)peak, 1.0 and 1.2] is seen only in the inner regions (,10 kpc) of the host galaxies and that it becomes weaker with radius due to the decreasing contribution of the red GC (V,I > 1.1) subpopulation. It is also found (both around M87 and around NGC 4552) that while the spatial distribution of the red GCs is as centrally concentrated as the host galaxy halo light distribution, the distribution of the blue GCs (V,I, 1.1) tends to be more extended. However, the blue GC distribution around M87 is not as extended as the Virgo cluster mass density profile. Based on these facts, we argue that the contribution of GCs associated with the Virgo cluster [e.g. intergalactic GCs (i-GCs)] is not significant around M87 and is not the primary reason for the high SN value of M87. Instead, most of the blue GCs around luminous ellipticals, as well as the red GCs, are presumed to be associated with the host galaxy. We model the radial profile of GC surface densities out to ,0.5 Mpc from M87 by a superposition of the GC populations associated with M87 and with NGC 4552. It is found that there are some regions where the GC surface densities are larger than that which is expected from this model, suggesting the existence of an additional i-GC population independent of the luminous ellipticals. By comparing the estimated i-GC surface density with the luminosity density of the intracluster stellar population inferred from the intergalactic planetary nebulae in the Virgo cluster, we obtain a crude estimate of i-GC specific frequency SN= 2.9+4.2,1.5. If this SN value represents the stellar population tidally stripped by a massive central galaxy from other (less-luminous) galaxies, the contribution of tidally captured GCs in the GC population of M87 would need to be low to be consistent with the high SN value of M87. [source]

A Subaru/Suprime-Cam wide-field survey of globular cluster populations around M87 , I. Observation, data analysis and luminosity function

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2006
Naoyuki Tamura
ABSTRACT In this paper and a companion paper, we report on a wide-field imaging survey of the globular cluster (GC) populations around M87 carried out with Suprime-Cam on the 8.2-m Subaru telescope. Here, we describe the observations, data reduction and data analysis, and present luminosity functions of GC populations around M87 and NGC 4552, another luminous Virgo elliptical in our survey field. The imaging data were taken in the B, V and I bands with a sky coverage of extending from the M87 centre out to ,0.5 Mpc. GC candidates were selected by applying a colour criterion on the B,V and V,I diagram to unresolved objects, which greatly reduces contamination. The data from control fields taken with Subaru/Suprime-Cam were also analysed for subtraction of contamination in the GC sample. These control field data are compatible with those in the M87 field in terms of the filter set (BVI), limiting magnitudes and image quality, which minimize the possibility of introducing any systematic errors into the subtractive correction. We investigate GC luminosity functions (GCLFs) at distances , 10 arcmin (,45 kpc) from the host galaxy centre in detail. By fitting Gaussians to the GCLFs, the V -band turnover magnitude (VTO) is estimated to be 23.62 ± 0.06 and 23.56 ± 0.20 mag for the GC population in M87 and NGC 4552, respectively. The GCLF is found to be a function of GC colour; VTO of the red GC subpopulation (V,I > 1.1) is fainter than that of the blue GC subpopulation (V,I, 1.1) in both M87 and NGC 4552, as expected if the colour differences are primarily due to a metallicity effect, and the mass functions of the two subpopulations are similar. The radial dependence of the GCLF is also investigated for the GC population in M87. The GCLF of each subpopulation at 1 ,R, 5 arcmin is compared to that at 5 ,R, 10 arcmin, but no significant trend with distance is found in the shape of the GCLF. We also estimate GC-specific frequencies (SN) for M87 and NGC 4552. The SN of the M87 GC population is estimated to be 12.5 ± 0.8 within 25 arcmin. The SN value of the NGC 4552 GC population is estimated to be 5.0 ± 0.6 within 10 arcmin. [source]

Mid-Infrared Imaging and Spectroscopic Observations of the Galactic Center with Subaru/COMICS

ASTRONOMISCHE NACHRICHTEN, Issue S1 2003
Y. Okada
Abstract We report the results of mid-infrared (7.8,m,13.2 ,m) high-spatial resolution imaging and spectroscopic observations of the Galactic center region with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the Subaru telescope. The images clearly show bright infrared sources and small structures in the diffuse emission. The spectra of all the observed positions show the 9.7 ,m silicate absorption feature. After corrected for the empirically-derived extinction, the intrinsic spectra of the infrared sources show either strong silicate emission or absorption, while the intrinsic diffuse emission has a power-law type spectrum. This difference indicates a possibility of dust processing due to the interaction between the infrared sources and their surrounding medium or a different origin of the dust grains surrounding the sources from those in the diffuse region. [source]

Subaru tackles a knotty problem

ASTRONOMY & GEOPHYSICS, Issue 4 2009
Article first published online: 20 JUL 200
Near-infrared observations of the Helix Nebula show that the comet-shaped knots found there are more abundant than thought, with many thousands picked out by the Subaru telescope. [source]