C. Darren Dowell

350 μm Dust Emission from High-Redshift Quasars

We report detections of six high-redshift (1.8 ≤ z ≤ 6.4), optically luminous, radio-quiet quasars at 350 μm, using the SHARC II bolometer camera at the Caltech Submillimeter Observatory. Our observations double the number of high-redshift quasars for which 350 μm photometry is available. By combining the 350 μm measurements with observations at other submillimeter/millimeter wavelengths, for each source we have determined the temperature of the emitting dust (ranging from 40 to 60 K) and the far-infrared luminosity [(0.6-2.2) × 10^(13) L⊙]. The combined mean spectral energy distribution of all high-redshift quasars with two or more rest-frame far-infrared photometric measurements is best fit with a graybody with temperature of 47 ± 3 K and a dust emissivity power-law spectral index of β = 1.6 ± 0.1. This warm dust component is a good tracer of the starburst activity of the quasar host galaxy. The ratio of the far-infrared to radio luminosities of infrared-luminous, radio-quiet high-redshift quasars is consistent with that found for local star-forming galaxies.

ANCHORING MAGNETIC FIELD IN TURBULENT MOLECULAR CLOUDS

One of the key problems in star formation research is to determine the role of magnetic fields. Starting from the atomic intercloud medium which has density n H ~ 1 cm–3, gas must accumulate from a volume several hundred pc across in order to form a typical molecular cloud. Star formation usually occurs in cloud cores, which have linear sizes below 1 pc and densities n H2 > 105 cm–3. With current technologies, it is hard to probe magnetic fields at scales lying between the accumulation length and the size of cloud cores, a range corresponds to many levels of turbulent eddy cascade, and many orders of magnitude of density amplification. For field directions detected from the two extremes, however, we show here that a significant correlation is found. Comparing this result with molecular cloud simulations, only the sub-Alfvenic cases result in field orientations consistent with our observations.

HerMES: CANDIDATE HIGH-REDSHIFT GALAXIES DISCOVERED WITH HERSCHEL/SPIRE*, **

We present a method for selecting z > 4 dusty, star-forming galaxies (DSFGs) using Herschel/Spectral and Photometric Imaging Receiver 250/350/500 μm flux densities to search for red sources. We apply this method to 21 deg2 of data from the HerMES survey to produce a catalog of 38 high-z candidates. Follow-up of the first five of these sources confirms that this method is efficient at selecting high-z DSFGs, with 4/5 at z = 4.3-6.3 (and the remaining source at z = 3.4), and that they are some of the most luminous dusty sources known. Comparison with previous DSFG samples, mostly selected at longer wavelengths (e.g., 850 μm) and in single-band surveys, shows that our method is much more efficient at selecting high-z DSFGs, in the sense that a much larger fraction are at z > 3. Correcting for the selection completeness and purity, we find that the number of bright (S 500 μm ≥ 30 mJy), red Herschel sources is 3.3 ± 0.8 deg–2. This is much higher than the number predicted by current models, suggesting that the DSFG population extends to higher redshifts than previously believed. If the shape of the luminosity function for high-z DSFGs is similar to that at z ~ 2, rest-frame UV based studies may be missing a significant component of the star formation density at z = 4-6, even after correction for extinction.

FAR-INFRARED POLARIMETRY OF GALACTIC CLOUDS FROM THE KUIPER AIRBORNE OBSERVATORY

In this paper we present a complete summary of the data obtained with the far-infrared polarimeter, Stokes, in flights of the Kuiper Airborne Observatory. We have observed 12 Galactic clouds and have made over 1100 individual measurements at 100 ?m and 60 ?m. The median P for all of the 60 ?m and 100 ?m measurements is 3.6% and 2.6% respectively. We also present flux maps obtained simultaneously with the polarimetry.

350 μm POLARIMETRY FROM THE CALTECH SUBMILLIMETER OBSERVATORY

We present a summary of data obtained with the 350 {mu}m polarimeter, Hertz, at the Caltech Submillimeter Observatory. We give tabulated results and maps showing polarization vectors and intensity contours. The summary includes over 4300 individual measurements in 56 Galactic sources and two galaxies. Of these measurements, 2153 have P {>=} 3{sigma} {sub p} statistical significance. The median polarization of the entire data set is 1.46%.

On the Measurement of the Magnitude and Orientation of the Magnetic Field in Molecular Clouds

We demonstrate that the combination of Zeeman, polarimetry, and ion-to-neutral molecular line width ratio measurements permits the determination of the magnitude and orientation of the magnetic field in the weakly ionized parts of molecular clouds. Zeeman measurements provide the strength of the magnetic field along the line of sight, polarimetry measurements give the field orientation in the plane of the sky, and the ion-to-neutral molecular line width ratio determines the angle between the magnetic field and the line of sight. We apply the technique to the M17 star-forming region using a HERTZ 350 μm polarimetry map and HCO+-to-HCN molecular line width ratios to provide the first three-dimensional view of the magnetic field in M17.

SHARC-II 350 μm OBSERVATIONS OF THERMAL EMISSION FROM WARM DUST IN z ⩾ 5 QUASARS

We present observations of four z ≥ 5 SDSS quasars at 350 μm with the SHARC-II bolometer camera on the Caltech Submillimeter Observatory. These are among the deepest observations that have been made by SHARC-II at 350 μm, and three quasars are detected at ≥3σ significance, greatly increasing the sample of 350 μm (corresponds to rest frame wavelengths of <60 μm at z ≥ 5), detected high-redshift quasars. The derived rest frame far-infrared (FIR) emission in the three detected sources is about five to ten times stronger than that expected from the average spectral energy distribution (SED) of the local quasars given the same 1450 A luminosity. Combining the previous submillimeter and millimeter observations at longer wavelengths, the temperatures of the FIR-emitting warm dust from the three quasar detections are estimated to be in the range of 39-52 K. Additionally, the FIR-to-radio SEDs of the three 350 μm detections are consistent with the emission from typical star-forming galaxies. The FIR luminosities are ~1013 L ☉ and the dust masses are ≥108 M ☉. These results confirm that huge amounts of warm dust can exist in the host galaxies of optically bright quasars as early as z ~ 6. The universe is so young at these epochs (~1 Gyr) that a rapid dust-formation mechanism is required. We estimate the size of the FIR dust-emission region to be about a few kpc, and further provide a comparison of the SEDs among different kinds of dust-emitting sources to investigate the dominant dust-heating mechanism.

Spatially Resolved Imaging at 350 μm of Cold Dust in Nearby Elliptical Galaxies

Continuum observations at 350 μm of seven nearby elliptical galaxies for which CO gas disks have recently been resolved with interferometry mapping are presented. These SHARC II mapping results provide the first clearly resolved far-infrared (FIR)-to-submillimeter continuum emission from cold dust (with temperatures 31 K T 23 K ) of any elliptical galaxy at a distance >40 Mpc. The measured FIR excess shows that the most likely and dominant heating source of this dust is not dilute stellar radiation or cooling flows, but rather star formation that could have been triggered by an accretion or merger event and fueled by dust-rich material that has settled in a dense region cospatial with the central CO gas disks. The dust is detected even in two cluster ellipticals that are deficient in H I, showing that, unlike H I, cold dust and CO in ellipticals can survive in the presence of hot X-ray gas, even in galaxy clusters. No dust cooler than 20 K, either distributed outside the CO disks or cospatial with and heated by the entire dilute stellar optical galaxy (or very extended H I), is currently evident.

First Constraints on Source Counts at 350 μm

We have imaged a ~6 arcmin2 region in the Bootes Deep Field using the 350 μm-optimized second-generation Submillimeter High Angular Resolution Camera (SHARC II), achieving a peak 1 σ sensitivity of ~5 mJy. We detect three sources above 3 σ, and determine a spurious source detection rate of 1.09 in our maps. In the absence of 5 σ detections, we rely on deep 24 μm and 20 cm imaging to deduce which sources are most likely to be genuine, giving two real sources. From this we derive an integral source count of 0.84 sources arcmin-2 at S > 13 mJy, which is consistent with 350 μm source count models that have an IR-luminous galaxy population evolving with redshift. We use these constraints to consider the future for ground-based short-submillimeter surveys.

Status of the SPIRE photometer data processing pipelines during the early phases of the Herschel Mission

We describe the current state of the ground segment of Herschel-SPIRE photometer data processing, approximately one year into the mission. The SPIRE photometer operates in two modes: scan mapping and chopped point source photometry. For each mode, the basic analysis pipeline - which follows in reverse the effects from the incidence of light on the telescope to the storage of samples from the detector electronics - is essentially the same as described pre-launch. However, the calibration parameters and detailed numerical algorithms have advanced due to the availability of commissioning and early science observations, resulting in reliable pipelines which produce accurate and sensitive photometry and maps at 250, 350, and 500 μm with minimal residual artifacts. We discuss some detailed aspects of the pipelines on the topics of: detection of cosmic ray glitches, linearization of detector response, correction for focal plane temperature drift, subtraction of detector baselines (offsets), absolute calibration, and basic map making. Several of these topics are still under study with the promise of future enhancements to the pipelines.