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FLAIR-II spectroscopy of two DENIS J-band galaxy samples | | Gary A. Mamon
; Quentin A. Parker
; Dominique Proust
; | | Date: |
16 Jul 2001 | | Journal: | PASA 18, 232-242 (2001) | | Subject: | astro-ph | | Affiliation: | 1,2), Quentin A. Parker (3,4), Dominique Proust ( IAP, Paris, France, DAEC, Obs. de Paris, Meudon, France, IfA, RoE, Edinburgh, UK, AAO, Coonabarabran, Australia | | Abstract: | As a pilot survey for the forthcoming 6dF Galaxy Redshift Survey, spectroscopy of galaxies selected in J (1.2 mu) with the DENIS survey was performed at the UKST using the FLAIR II multi-object spectroscope. 69 galaxy redshifts (z’s) were obtained in a high |b| field and an additional 12 z’s in a low latitude (b=-17 deg), obscured field. This study illustrates the feasibility of obtaining z’s with optical spectra on galaxies selected at much longer wavelengths. It validated a very preliminary algorithm for star/galaxy separation for high |b| DENIS objects, with 99% reliability for J < 13.9. However, the FLAIR II z determinations required substantially longer integration times to achieve 90% completeness than expected from previous optical surveys at comparable depth. This is mainly due to a degradation in overall fibre throughput due to known problems with ageing of the prism-cement-fibre interface with exposure to UV light. Our low |b| (high extinction) field required 2.5 times more exposure time for less than 50% of successful z measurements. Among the J <= 13.9 galaxies with measured z’s, only 37+/-6% display emission lines, in comparison with 60% of emission-line galaxies (ELGs) in optical samples of comparable depth. The ELGs are, on average, 0.5 mag bluer in B-J than non-ELGs of the same luminosity. We confirm a previous optically-based result that the fraction of ELGs increases rapidly with decreasing galaxy luminosity. The J-band luminosity function is estimated. Our high latitude field displays a concentration of galaxies at cz ~ 38000 km/s suggesting a possible supercluster. A radial velocity is reported for a galaxy lying near the projected centre of the Abell 1434 cluster of galaxies, for which no cluster z is currently available. | | Source: | arXiv, astro-ph/0107268 | | Services: | Forum | Review | PDF | Favorites | |
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