106 research outputs found
Future Developments in Low Temperature Detectors for CMB and Submm Astronomy
We summarize the wide range of current and upcoming developments in low temperature detectors for CMB and submillimeter astronomy. We discuss work in sensor development, photon coupling and filtering architectures, and polarimetry and how these tie to applications requirements
Sunyaev-Zeldovich Effect Studies of Galaxy Clusters with Bolocam (and Future Instrumentation)
Galaxy clusters are excellent laboratories for studying the astrophysics of gravitational collapse and the non-self-similar processes that can affect it. A number of different techniques allow us to study the distribution of the consituents of galaxy clusters. The thermal Sunyaev-Zeldovich effect measures the line-of-sight integral of the the pressure in the ICM plasma. Comparison to and combination with other probes enables a variety of studies of the ICM and of clusters: scaling relations, radial profiles, tests of hydrostatic equilibrium, etc. We report on the status of our program to image clusters in the thermal Sunyaev-Zeldovich effect at 150 GHz using Bolocam and perform such tests. We also describe the upcoming MKIDCam long-wavelength multi-color facility camera for the CSO, which will provide new capabilities in thermal Sunyaev-Zeldovich effect imaging. We comment on the role Tom Phillips and the CSO have played in facilitating the development of mm-wave SZ observations
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
A high signal to noise ratio map of the Sunyaev-Zel'dovich increment at 1.1 mm wavelength in Abell 1835
We present an analysis of an 8 arcminute diameter map of the area around the
galaxy cluster Abell 1835 from jiggle map observations at a wavelength of 1.1
mm using the Bolometric Camera (Bolocam) mounted on the Caltech Submillimeter
Observatory (CSO). The data is well described by a model including an extended
Sunyaev-Zel'dovich (SZ) signal from the cluster gas plus emission from two
bright background submm galaxies magnified by the gravitational lensing of the
cluster. The best-fit values for the central Compton value for the cluster and
the fluxes of the two main point sources in the field: SMM J140104+0252, and
SMM J14009+0252 are found to be ,
6.5 mJy and 11.3 mJy, where the first error
represents the statistical measurement error and the second error represents
the estimated systematic error in the result. This measurement assumes the
presence of dust emission from the cluster's central cD galaxy of
mJy, based on higher frequency observations of Abell 1835. The cluster image
represents one of the highest-significance SZ detections of a cluster in the
positive region of the thermal SZ spectrum to date. The inferred central
intensity is compared to other SZ measurements of Abell 1835 and this
collection of results is used to obtain values for and the cluster peculiar velocity km/s.Comment: 9 pages, 5 figure
Thermodynamic Profiles of Galaxy Clusters from a Joint X-ray/SZ Analysis
We jointly analyze Bolocam Sunyaev-Zeldovich (SZ) effect and Chandra X-ray
data for a set of 45 clusters to derive gas density and temperature profiles
without using spectroscopic information. The sample spans the mass and redshift
range
and . We define cool-core (CC) and non-cool core (NCC)
subsamples based on the central X-ray luminosity, and 17/45 clusters are
classified as CC. In general, the profiles derived from our analysis are found
to be in good agreement with previous analyses, and profile constraints beyond
are obtained for 34/45 clusters. In approximately 30% of the CC
clusters our analysis shows a central temperature drop with a statistical
significance of ; this modest detection fraction is due mainly to a
combination of coarse angular resolution and modest S/N in the SZ data. Most
clusters are consistent with an isothermal profile at the largest radii near
, although 9/45 show a significant temperature decrease with
increasing radius. The sample mean density profile is in good agreement with
previous studies, and shows a minimum intrinsic scatter of approximately 10%
near . The sample mean temperature profile is consistent
with isothermal, and has an intrinsic scatter of approximately 50% independent
of radius. This scatter is significantly higher compared to earlier X-ray-only
studies, which find intrinsic scatters near 10%, likely due to a combination of
unaccounted for non-idealities in the SZ noise, projection effects, and sample
selection.Comment: 42 pages, 52 figure
A multi-chroic kinetic inductance detectors array using hierarchical phased array antenna
We present a multi-chroic kinetic inductance detector (KID) pixel design
integrated with a broadband hierarchical phased-array antenna. Each
low-frequency pixel consists of four high-frequency pixels. Four passbands are
designed from 125 to 365 GHz according to the atmospheric windows. The lumped
element KIDs are designed with 100 nm Al as the inductor and with Nb parallel
plate capacitors using hydrogenated amorphous Si as the dielectric. Due to the
broadband coverage, two different types of structures are needed to couple
light from microstrip lines to the KIDs. The KIDs designs are optimized for a
10-m-class telescope at a high, dry site.Comment: 6 pages, 4 figures, submitted to Journal of Low Temperature Physic
A Comparison and Joint Analysis of Sunyaev-Zel'dovich Effect Measurements from Planck and Bolocam for a set of 47 Massive Galaxy Clusters
We measure the SZ signal toward a set of 47 clusters with a median mass of
M and a median redshift of 0.40 using data from
Planck and the ground-based Bolocam receiver. When Planck XMM-like masses are
used to set the scale radius , we find consistency between
the integrated SZ signal, , derived from Bolocam and Planck
based on gNFW model fits using A10 shape parameters, with an average ratio of
(allowing for the % Bolocam flux calibration
uncertainty). We also perform a joint fit to the Bolocam and Planck data using
a modified A10 model with the outer logarithmic slope allowed to vary,
finding (measurement error followed by
intrinsic scatter). In addition, we find that the value of scales with
mass and redshift according to . This mass scaling is in good agreement with recent
simulations. We do not observe the strong trend of with redshift seen
in simulations, though we conclude that this is most likely due to our sample
selection. Finally, we use Bolocam measurements of to test the
accuracy of the Planck completeness estimate. We find consistency, with the
actual number of Planck detections falling approximately below the
expectation from Bolocam. We translate this small difference into a constraint
on the the effective mass bias for the Planck cluster cosmology results, with
.Comment: Updated to include one additional co-author. Also some minor changes
to the text based on initial feedbac
The large Atacama submillimeter telescope
Cornell and Caltech are undertaking a two year conceptual design study for a 25-m class sub-mm telescope. The nominal location for this facility will be the high Atacama Desert of Northern Chile. The baseline design is a segmented mirror telescope optimized for operation at wavelengths longer than 200 microns to take advantage of a low precipitable water vapor at the site. We discuss science drivers and their implications for telescope design and technical requirements, and planned technical study areas
- …