Extremely Large Telescope

Abstract:

We present preliminary results from a programme to obtain multi-object near-infrared spectroscopy of galaxies at redshifts 0.7 < z < 1.5. We are using the instrument CIRPASS (the Cambridge Infra-Red PAnoramic Survey Spectrograph), in multi-object mode, to survey Hα in galaxies at z ∼ 1. We aim to address the true star formation history of the Universe at this epoch: potentially the peak period of star formation activity. Hα is the same star formation measure used at low redshift, and hence we can trace star formation without the systematic uncertainties of using different calibrators in different redshift bins, or the extreme dust extinction in the rest-ultraviolet (rest-UV). CIRPASS has been successfully demonstrated in multi-object mode on the Anglo-Australian Telescope (AAT) and the William Herschel Telescope (WHT). Here we present preliminary results from one of our fields, the Hubble Deep Field North, observed with the WHT. With 150 fibres deployed over an unvignetted field of ∼15 arcmin, we have several detections of Hα from star-forming galaxies at 0.8 < z < 1.0 and present spectra of the seven brightest of these. By pre-selecting galaxies with redshifts such that Hα will appear between the OH sky lines, we can detect star formation rates of 5 h-270 M⊙ yr-1 (5 δ in 3 hours, ΩM = 0.3, ΩΛ = 0.7). It appears that star formation rates inferred from Ha are, on average, a factor of more than two higher than those based on the UV continuum alone.

Abstract:

VLT J- to M'-band adaptive optics observations of the Circinus galaxy on parsec scales resolve a central bright Ks-band source with a FWHM size of 1.9 ± 0.6 pc. This source is only visible at wavelengths longward of 1.6 μm and coincides in position with the peak of the [Si VII] 2.48 μm coronal line emission. With respect to the peak of the central optical emission, the source is shifted by ∼0″15 (2.8 pc) to the southeast. Indeed, the Ks-band source defines the vertex of a fairly collimated beam that extends for ∼10 pc and is seen in both continuum light shortward of 1.6 μm and in Hα line emission. The source also lies at the center of a ∼19 pc size [Si VII] ionization bicone. Identifying this source as the nucleus of Circinus, its size is compatible with a putative parsec-scale torus. Its spectral energy distribution, characterized by a prominent narrow peak, is compatible with a dust temperature of 300 K. Hotter dust within a 1 pc radius of the center is not detected. The active galactic nucleus (AGN) luminosity required to heat this dust is in the range of X-ray luminosities that have been measured toward the central source. This in turn supports the existence of highly obscuring material, with column densities of 10²⁴ cm ². that must be located within 1 pc of the core.

Abstract:

To examine the evolution of the early-type galaxy population in the rich cluster Abell 2390 at z=0.23 we have gained spectroscopic data of 51 elliptical and lenticular galaxies with MOSCA at the 3.5 m telescope on Calar Alto Observatory. This investigation spans both a broad range in luminosity (-19.3>M_B>-22.3) and uses a wide field of view of 10'x10', therefore the environmental dependence of different formation scenarios can be analysed in detail as a function of radius from the cluster centre. Here we present results on the surface brightness modelling of galaxies where morphological and structural information is available in the F814W filter aboard the Hubble Space Telescope (HST) and investigate for this subsample the evolution of the Fundamental Plane.

Abstract:

We introduce the NOAO Fundamental Plane Survey (NFPS), a wide-field imaging/spectroscopic study of rich, low-redshift galaxy clusters. The survey targets X-ray-selected clusters at 0.010 < z < 0.067, distributed over the whole sky, with imaging and spectroscopic observations obtained for 93 clusters. This data set will be used in investigations of galaxy properties in the cluster environment and of large-scale velocity fields through the fundamental plane. In this paper, we present details of the cluster sample construction and the strategies employed to select early-type galaxy samples for spectroscopy. Details of the spectroscopic observations are reported. From observations of 5479 red galaxies, we present redshift measurements for 5388 objects and internal velocity dispersions for 4131. The velocity dispersions have a median estimated error ∼7%. The NFPS has ∼15% overlap with previously published velocity dispersion data sets. Comparisons to these external catalogs are presented and indicate typical external errors of ∼8%.

Abstract:

We present the result of a decomposition of the 2dF Galaxy Redshift Survey (2dFGRS) galaxy overdensity field into an orthonormal basis of spherical harmonics and spherical Bessel functions. Galaxies are expected to directly follow the bulk motion of the density field on large scales, so the absolute amplitude of the observed large-scale redshift-space distortions caused by this motion is expected to be independent of galaxy properties. By splitting the overdensity field into radial and angular components, we linearly model the observed distortion and obtain the cosmological constraint Ω m0.6σ8 = 0.46 ± 0.06. The amplitude of the linear redshift-space distortions relative to the galaxy overdensity field is dependent on galaxy properties and, for L* galaxies at redshift z = 0, we measure β(L*, 0) = 0.58 ± 0.08, and the amplitude of the overdensity fluctuations b(L *, 0)σ8 = 0.79 ± 0.03, marginalizing over the power spectrum shape parameters. Assuming a fixed power spectrum shape consistent with the full Fourier analysis produces very similar parameter constraints.