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Spectroscopic Survey (spectroscopic + survey)
Selected AbstractsA spectroscopic survey of EC4, an extended cluster in Andromeda's halo,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009M. L. M. Collins ABSTRACT We present a spectroscopic survey of candidate red giant branch stars in the extended star cluster, EC4, discovered in the halo of M31 from our Canada,France,Hawaii Telescope/MegaCam survey, overlapping the tidal streams, Streams ,Cp' and ,Cr'. These observations used the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope to obtain spectra around the Caii triplet region with ,1.3 Å resolution. Six stars lying on the red giant branch within two core radii of the centre of EC4 are found to have an average vr=,287.9+1.9,2.4 km s,1 and ,v,corr = 2.7+4.2,2.7 km s,1, taking instrumental errors into account. The resulting mass-to-light ratio for EC4 is M/L = 6.7+15,6.7 M,/L,, a value that is consistent with a globular cluster within the 1, errors we derive. From the summed spectra of our member stars, we find EC4 to be metal-poor, with [Fe/H]=,1.6 ± 0.15. We discuss several formation and evolution scenarios which could account for our kinematic and metallicity constraints on EC4, and conclude that EC4 is most comparable with an extended globular cluster. We also compare the kinematics and metallicity of EC4 with Streams ,Cp' and ,Cr', and find that EC4 bears a striking resemblance to Stream ,Cp' in terms of velocity, and that the two structures are identical in terms of both their spectroscopic and photometric metallicities. From this, we conclude that EC4 is likely related to Stream ,Cp'. [source] Discovery of 17 new sharp-lined Ap stars with magnetically resolved lines,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008L. M. Freyhammer ABSTRACT Chemically peculiar A stars (Ap) are extreme examples of the interaction of atomic element diffusion processes with magnetic fields in stellar atmospheres. The rapidly oscillating Ap stars provide a means for studying these processes in three dimensions and are at the same time important for studying the pulsation excitation mechanism in A stars. As part of the first comprehensive, uniform, high-resolution spectroscopic survey of Ap stars, which we are conducting in the Southern hemisphere with the Michigan Spectral Catalogues as the basis of target selection, we report here the discovery of 17 new magnetic Ap stars having spectroscopically resolved Zeeman components from which we derive magnetic field moduli in the range 3,30 kG. Among these are (1) the current second strongest known magnetic A star, (2) a double-lined Ap binary with a magnetic component and (3) an A star with particularly peculiar and variable abundances. Polarimetry of these stars is needed to constrain their field geometries and to determine their rotation periods. We have also obtained an additional measurement of the magnetic field of the Ap star HD 92499. [source] Luminous red galaxy clustering at z, 0.7 , first results using AAOmegaMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008Nicholas P. Ross ABSTRACT We report on the AAT-AAOmega LRG Pilot observing run to establish the feasibility of a large spectroscopic survey using the new AAOmega instrument. We have selected luminous red galaxies (LRGs) using single epoch SDSS riz -photometry to i < 20.5 and z < 20.2. We have observed in three fields including the COSMOS field and the COMBO-17 S11 field, obtaining a sample of ,600 redshift z, 0.5 LRGs. Exposure times varied from 1,4 h to determine the minimum exposure for AAOmega to make an essentially complete LRG redshift survey in average conditions. We show that LRG redshifts to i < 20.5 can be measured in ,1.5 h exposures and present comparisons with 2SLAQ and COMBO-17 (photo)redshifts. Crucially, the riz selection coupled with the three to four times improved AAOmega throughput is shown to extend the LRG mean redshift from z= 0.55 for 2SLAQ to z= 0.681 ± 0.005 for riz -selected LRGs. This extended range is vital for maximizing the signal-to-noise ratio for the detection of the baryon acoustic oscillations (BAOs). Furthermore, we show that the amplitude of LRG clustering is s0= 9.9 ± 0.7h,1 Mpc, as high as that seen in the 2SLAQ LRG Survey. Consistent results for this clustering amplitude are found from the projected and semi-projected correlation functions. This high amplitude is consistent with a long-lived population whose bias evolves as predicted by a simple ,high-peak' model. We conclude that a redshift survey of 360 000 LRGs over 3000 deg2, with an effective volume some four times bigger than previously used to detect BAO with LRGs, is possible with AAOmega in 170 nights. [source] The lithium depletion boundary and the age of NGC 2547MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2003J. M. Oliveira ABSTRACT We present the results of a photometric and spectroscopic survey of cool M dwarf candidates in the young open cluster NGC 2547. Using the 2dF fibre spectrograph, we have searched for the luminosity at which lithium remains unburned in an attempt to constrain the cluster age. The lack of a population of individual lithium-rich objects towards the faint end of our sample places a very strong lower limit to the cluster age of 35 Myr. However, the detection of lithium in the averaged spectra of our faintest targets suggests that the lithium depletion boundary lies at 9.5 < MI < 10.0 and that the cluster age is <54 Myr. The age of NGC 2547 judged from fitting isochrones to low-mass pre-main-sequence stars in colour,magnitude diagrams is 20,35 Myr using the same evolutionary models. The sense and size of the discrepancy in age determined by these two techniques is similar to that found in another young cluster, IC 2391, and in the low-mass pre-main-sequence binary system, GJ 871.1AB. We suggest that the inclusion of rotation or dynamo-generated magnetic fields in the evolutionary models could reconcile the two age determinations, but only at the expense of increasing the cluster ages beyond that currently indicated by the lithium depletion. Alternatively, some mechanism is required that increases the rate of lithium depletion in young, very low-mass fully convective stars. [source] A composite K -band luminosity function for cluster galaxiesASTRONOMISCHE NACHRICHTEN, Issue 9-10 2009R. De Propris Abstract We present a composite K -band luminosity function for 10 clusters at low redshift, where member galaxies are identified from an existing spectroscopic survey (the 2dF galaxy redshift survey). Our kinematically selected K -band luminosity function is well fitted by a Schechter function with MK * = ,24.50 + 5 log h and , = ,0.98 over ,27 , MK ,5 log h < ,22. This is very similar to the 2dF field value and suggests that the integrated mass accretion history of galaxies does not vary strongly with environment (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Beating lensing cosmic variance with galaxy tomographyMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2004Ue-Li Pen ABSTRACT We discuss the use of cross-correlations between galaxies with distance information and projected weak lensing dark matter maps to obtain a fully three-dimensional dark matter map and power spectrum. On large scales (l, 100) one expects the galaxies to be biased, but not stochastic. I show that this allows a simultaneous solution of the full three-dimensional evolving galaxy bias and the dark matter power spectrum simultaneously. Within the photometric redshift information of the Canada,France,Hawaii (CFH) lensing legacy survey, this allows a threefold reduction of statistical error, while a cross-correlation with the Canadian Large Adaptive Reflector (CLAR) or other deep spectroscopic surveys allows a tenfold improvement in dark matter power accuracy on linear scales. This makes lensing surveys more sensitive to the cosmic equation of state and the neutrino masses. [source] | ||||||||||