Showing papers by "Jason Glenn published in 2006"

Bolocam survey for 1.1 mm dust continuum emission in the c2d legacy clouds. II. Ophiuchus

Abstract: We present a large-scale millimeter continuum map of the Ophiuchus molecular cloud. Nearly 11 deg2, including all of the area in the cloud with AV ≥ 3 mag, was mapped at 1.1 mm with Bolocam on the Caltech Submillimeter Observatory (CSO). By design, the map also covers the region mapped in the infrared with the Spitzer Space Telescope. We detect 44 definite sources, and a few likely sources are also seen along a filament in the eastern streamer. The map indicates that dense cores in Ophiuchus are very clustered and often found in filaments within the cloud. Most sources are round, as measured at the half-power point, but elongated when measured at lower contour levels, suggesting spherical sources lying within filaments. The masses, for an assumed dust temperature of 10 K, range from 0.24 to 3.9 M☉, with a mean value of 0.96 M☉. The total mass in distinct cores is 42 M☉, 0.5%-2% of the total cloud mass, and the total mass above 4 σ is about 80 M☉. The mean densities in the cores are quite high, with an average of 1.6 × 106 cm-3, suggesting short free-fall times. The core mass distribution can be fitted with a power law with slope α = 2.1 ± 0.3 for M > 0.5 M☉, similar to that found in other regions, but slightly shallower than that of some determinations of the local IMF. In agreement with previous studies, our survey shows that dense cores account for a very small fraction of the cloud volume and total mass. They are nearly all confined to regions with AV ≥ 9 mag, a lower threshold than found previously.

Herschel-SPIRE: Design, Performance, and Scientific Capabilities

Abstract: SPIRE, the Spectral and Photometric Imaging Receiver, is a submillimetre camera and spectrometer for the European Space Agency's Herschel Space Observatory. It comprises a three-band imaging photometer operating at 250, 360 and 520

The Bolocam 1.1 mm Lockman Hole Galaxy Survey: SHARC II 350 μm Photometry and Implications for Spectral Models, Dust Temperatures, and Redshift Estimation

Abstract: We present 350 ?m photometry of all 17 galaxy candidates in the Lockman Hole detected in a 1.1 mm Bolocam survey. Several of the galaxies were previously detected at 850 ?m, at 1.2 mm, in the infrared by Spitzer, and in the radio. Nine of the Bolocam galaxy candidates were detected at 350 ?m, and two new candidates were serendipitously detected at 350 ?m (bringing the total in the literature detected in this way to three). Five of the galaxies have published spectroscopic redshifts, enabling investigation of the implied temperature ranges and a comparison of photometric redshift techniques. For z ? 2.5 thermally emitting galaxies, ? = 350 ?m lies near the spectral energy distribution peak. Thus, luminosities can be measured without extrapolating to the peak from detection wavelengths of ? ? 850 ?m. Characteristically, the galaxy luminosities lie in the range 1.0-1.2 ? 1013 L?, with dust temperatures in the range 40-70 K, depending on the choice of spectral index and wavelength of unit optical depth. The implied dust masses are ? 108 M?. We find that the far-infrared to radio relation for star-forming ULIRGs systematically overpredicts the radio luminosities and overestimates redshifts on the order of ?z ? 1, whereas redshifts based on either submillimeter data alone or the 1.6 ?m stellar bump and PAH features are more accurate.

Z-Spec: a broadband direct-detection millimeter-wave spectrometer -- instrument status and first results

Abstract: We report on the status of Z-Spec, including preliminary results of our first astronomical measurements. Z-Spec is a cryogenic, broadband, millimeter-wave grating spectrometer designed for molecular line surveys of galaxies, including carbon monoxide redshift measurements of high-redshift submillimeter sources. With an instantaneous bandwidth of 185-305 GHz, Z-Spec covers the entire 1 mm atmospheric transmission window with a resolving power of 200-400. The spectrometer employs the Waveguide Far-Infrared Spectrometer (WaFIRS) architecture, in which the light propagation is confined within a parallel-plate waveguide, resulting in a minimum mechanical envelope. Its array of 160 silicon-nitride micromesh bolometers is cooled to below 100 mK for background-limited performance. With its sensitivity, broad bandwidth, and compactness, Z-Spec serves as a prototype for a future far-IR spectrometer aboard a cold telescope in space. Z-Spec successfully demonstrated functionality with a partial array of detectors and warm electronics during a week-long engineering run at the Caltech Submillimeter Observatory in June, 2005. We describe the instrument performance evaluated at the telescope and in subsequent laboratory tests and compare these results with design specifications. Following several modifications we returned to the telescope in April, 2006. We present a preliminary astronomical spectrum and discuss our plans to improve sensitivity and throughput to achieve our ultimate science goals.

The Bolocam 1.1 mm Lockman Hole Galaxy Survey: SHARC II 350 micron Photometry and Implications for Spectral Models, Dust Temperatures, and Redshift Estimation

Abstract: We present 350 micron photometry of all 17 galaxy candidates in the Lockman Hole detected in a 1.1 mm Bolocam survey. Several of the galaxies were previously detected at 850 microns, at 1.2 mm, in the infrared by Spitzer, and in the radio. Nine of the Bolocam galaxy candidates were detected at 350 microns and two new candidates were serendipitously detected at 350 microns (bringing the total in the literature detected in this way to three). Five of the galaxies have published spectroscopic redshifts, enabling investigation of the implied temperature ranges and a comparison of photometric redshift techniques. Lambda = 350 microns lies near the spectral energy distribution peak for z = 2.5 thermally emitting galaxies. Thus, luminosities can be measured without extrapolating to the peak from detection wavelengths of lambda > 850 microns. Characteristically, the galaxy luminosities lie in the range 1.0 - 1.2 x 10^13 L_solar, with dust temperatures in the range of 40 K to 70 K, depending on the choice of spectral index and wavelength of unit optical depth. The implied dust masses are 3 - 5 x 10^8 M_solar. We find that the far-infrared to radio relation for star-forming ULIRGs systematically overpredicts the radio luminosities and overestimates redshifts on the order of Delta z ~ 1, whereas redshifts based on either on submillimeter data alone or the 1.6 micron stellar bump and PAH features are more accurate.

Optical performance characterisation of HERSCHEL/SPIRE

Abstract: The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel Space Observatory. The instrument covers 200 to 670 μm with a three band photometric camera and a two band imaging Fourier Transform Spectrometer (IFTS). In this paper we discuss the performance of the optics of the instrument as determined during the pre-flight instrument testing to date. In particular we concentrate on the response of the instrument to a point source, the comparison between the visible light alignment and the infrared alignment and the effect of the optical performance on the overall instrument sensitivity. We compare the empirical performance of the instrument optics to that expected from elementary diffraction theory.

Bolocam Survey for 1.1 mm Dust Continuum Emission in the c2d Legacy Clouds. II. Ophiuchus

Abstract: We present a large-scale millimeter continuum map of the Ophiuchus molecular cloud. Nearly 11 square degrees, including all of the area in the cloud with visual extinction more than 3 magnitudes, was mapped at 1.1 mm with Bolocam on the Caltech Submillimeter Observatory (CSO). By design, the map also covers the region mapped in the infrared with the Spitzer Space Telescope. We detect 44 definite sources, and a few likely sources are also seen along a filament in the eastern streamer. The map indicates that dense cores in Ophiuchus are very clustered and often found in filaments within the cloud. Most sources are round, as measured at the half power point, but elongated when measured at lower contour levels, suggesting spherical sources lying within filaments. The masses, for an assumed dust temperature of 10 K, range from 0.24 to 3.9 solar masses, with a mean value of 0.96 solar masses. The total mass in distinct cores is 42 solar masses, 0.5 to 2% of the total cloud mass, and the total mass above 4 sigma is about 80 solar masses. The mean densities in the cores are quite high, with an average of 1.6 x 10^6 per cc, suggesting short free-fall times. The core mass distribution can be fitted with a power law with slope of 2.1 plus or minus 0.3 for M>0.5 solar masses, similar to that found in other regions, but slightly shallower than that of some determinations of the local IMF. In agreement with previous studies, our survey shows that dense cores account for a very small fraction of the cloud volume and total mass. They are nearly all confined to regions with visual extinction at least 9 mag, a lower threshold than found previously.

Submillimeter Galaxy Surveys with AzTEC

Abstract: We describe a recent large scale survey of the Submillimeter Galaxy (SMG) population by AzTEC, a 144 element bolometer camera, on the 15m diameter James Clerk Maxwell Telescope. From November 2005 to February 2006, over 400 hours of telescope time were spent imaging over 1 square degree of sky with an area weighted target sensitivity of 0.7 mJy rms. Several fields with large multi-wavelength data sets were mapped including the Subaru/XMM-Newton Deep Survey field, the Lockmann Hole, GOODS-N, and a subset of the COSMOS field. In addition we mapped fields spanning a wide range of environments including several regions with known mass over-density. Together this represents the largest/deepest survey of the SMG population. Herein we report on the technical details of the surveys, describe the reduction pipeline, and show preliminary results from a subsection of the survey fields.

Z-Spec's first light at the Caltech Submillimeter Observatory

Abstract: We report the success of our first engineering run with Z-Spec, a new millimeter spectrograph on the 10 m Caltech Submillimeter Telescope during the first week of June 2005. The bolometric instrument is indeed the first of its kind, covering the atmospheric window from 187 to 310 GHz at the spectral resolution of 250–400, and will provide a critical follow-up study for discoveries by SCUBA and Bolocam. We present the spectrum of an ultra-luminous infrared galaxy NGG 6240 obtained by Z-Spec. Z-Spec serves as a prototype for future far-IR spectrometers on a cold space telescope where large gains in sensitivity are expected.