145,569 research outputs found
A large narrow band H survey at : the bright end of the luminosity function, cosmic variance and clustering across cosmic time
We carried out the largest ( Mpc, 26 deg) H
narrow band survey to date at in the SA22, W2 and XMMLSS
extragalactic fields. Our survey covers a large enough volume to overcome
cosmic variance and to sample bright and rare H emitters up to an
observed luminosity of erg s, equivalent to yr. Using our sample of sources brighter than
erg s ( yr), we derive H
luminosity functions, which are well described by a Schechter function with
Mpc and
erg s (with a fixed faint end slope ). We find that
surveys probing smaller volumes ( Mpc) are heavily
affected by cosmic variance, which can lead to errors of over per cent in
the characteristic density and luminosity of the H luminosity function.
We derive a star formation rate density of yr, in agreement with the redshift-dependent
H parametrisation from Sobral et al. (2013). The two-point correlation
function is described by a single power law , corresponding to a clustering length of Mpc/h. We find that the most luminous H emitters at
are more strongly clustered than the relatively fainter ones. The
H emitters at in our sample reside in
dark matter haloes. This implies that the most
star forming galaxies always reside in relatively massive haloes or group-like
environments and that the typical host halo mass of star-forming galaxies is
independent of redshift if scaled by , as
proposed by Sobral et al. (2010).Comment: Accepted for publication in MNRAS; 18 pages, 19 figures, 6 table
Millimeter-Wave Lumped Element Superconducting Bandpass Filters for Multi-Color Imaging
The opacity due to water vapor in the Earth's atmosphere obscures portions of the sub-THz spectrum (mm/sub-mm wavelengths) to ground based astronomical observation. For maximum sensitivity, instruments operating at these wavelengths must be designed to have spectral responses that match the available windows in the atmospheric transmission that occur in between the strong water absorption lines. Traditionally, the spectral response of mm/sub-mm instruments has been set using optical, metal-mesh bandpass filters [1]. An alternative method for defining the passbands, available when using superconducting detectors coupled with planar antennas, is to use on-chip, superconducting filters [2]. This paper presents the design and testing of superconducting, lumped element, on-chip bandpass filters (BPFs), placed inline with the microstrip connecting the antenna and the detector, covering the frequency range from 209–416 GHz. Four filters were designed with pass bands 209–274 GHz, 265–315 GHz, 335–361 GHz and 397–416 GHz corresponding to the atmospheric transmission windows. Fourier transform spectroscopy was used to verify that the spectral response of the BPFs is well predicted by the computer simulations. Two-color operation of the pixels was demonstrated by connecting two detectors to a single broadband antenna through two BPFs. Scalability of the design to multiple (four) colors is discussed
Pulse Shape Analysis and Identification of Multipoint Events in a Large-Volume Proportional Counter in an Experimental Search for 2K Capture Kr-78
A pulse shape analysis algorithm and a method for suppressing the noise
component of signals from a large copper proportional counter in the experiment
aimed at searching for 2K capture of Kr-78 are described. These signals
correspond to a compound event with different numbers of charge clusters due to
from primary ionization is formed by these signals. A technique for separating
single- and multipoint events and determining the charge in individual clusters
is presented. Using the Daubechies wavelets in multiresolutional signal
analysis, it is possible to increase the sensitivity and the resolution in
extraction of multipoint events in the detector by a factor of 3-4.Comment: 10 pages, 8 figures. submitted to Instruments and Experimental
Techniques; ISSN 0020/441
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