Patrick S. Broos

Bio: Patrick S. Broos is an academic researcher from Pennsylvania State University. The author has contributed to research in topics: Stars & Star formation. The author has an hindex of 60, co-authored 166 publications receiving 14764 citations. Previous affiliations of Patrick S. Broos include University of Wyoming.

The Swift Ultra-Violet/Optical Telescope

Abstract: The Ultra-Violet/Optical Telescope (UVOT) is one of three instruments flying aboard the Swift Gamma-ray Observatory. It is designed to capture the early (∼1 min) UV and optical photons from the afterglow of gamma-ray bursts in the 170–600 nm band as well as long term observations of these afterglows. This is accomplished through the use of UV and optical broadband filters and grisms. The UVOT has a modified Ritchey–Chretien design with micro-channel plate intensified charged-coupled device detectors that record the arrival time of individual photons and provide sub-arcsecond positioning of sources. We discuss some of the science to be pursued by the UVOT and the overall design of the instrument.

The Swift Ultra-Violet/Optical Telescope

Abstract: The UV/Optical Telescope (UVOT) is one of three instruments flying aboard the Swift Gamma-ray Observatory. It is designed to capture the early (approximately 1 minute) UV and optical photons from the afterglow of gamma-ray bursts in the 170-600 nm band as well as long term observations of these afterglows. This is accomplished through the use of UV and optical broadband filters and grisms. The UVOT has a modified Ritchey-Chretien design with micro-channel plate intensified charged-coupled device detectors that record the arrival time of individual photons and provide sub-arcsecond positioning of sources. We discuss some of the science to be pursued by the UVOT and the overall design of the instrument.

Photometric calibration of the Swift ultraviolet/optical telescope

Abstract: We present the photometric calibration of the Swift Ultraviolet/Optical Telescope (UVOT) which includes: optimum photometric and background apertures, effective area curves, colour transformations, conversion factors for count rates to flux and the photometric zero-points (which are accurate to better than 4 per cent) for each of the seven UVOT broad-band filters. The calibration was performed with observations of standard stars and standard star fields that represent a wide range of spectral star types. The calibration results include the position-dependent uniformity, and instrument response over the 1600‐8000 A operational range. Because the UVOT is a photon-counting instrument, we also discuss the effect of coincidence loss on the calibration results. We provide practical guidelines for using the calibration in UVOT data analysis. The results presented here supersede previous calibration results.

The Chandra Deep Field North Survey. XIII. 2 Ms Point-Source Catalogs

Abstract: We present point-source catalogs for the ?2 Ms exposure of the Chandra Deep Field North, currently the deepest X-ray observation of the universe in the 0.5?8.0 keV band. Five hundred and three (503) X-ray sources are detected over an ?448 arcmin2 area in up to seven X-ray bands. Twenty (20) of these X-ray sources lie in the central ?5.3 arcmin2 Hubble Deep Field North (13,600 sources deg-2). The on-axis sensitivity limits are ?2.5 ? 10-17 ergs cm-2 s-1 (0.5?2.0 keV) and ?1.4 ? 10-16 ergs cm-2 s-1 (2?8 keV). Source positions are determined using matched-filter and centroiding techniques; the median positional uncertainty is ?03. The X-ray colors of the detected sources indicate a broad variety of source types, although absorbed AGNs (including a small number of possible Compton-thick sources) are clearly the dominant type. We also match lower significance X-ray sources to optical counterparts and provide a list of 79 optically bright (R 23) lower significance Chandra sources. The majority of these sources appear to be starburst and normal galaxies. The average backgrounds in the 0.5?2.0 keV and 2?8 keV bands are 0.056 and 0.135 counts Ms-1 pixel-1, respectively. The background count distributions are very similar to Poisson distributions. We show that this ?2 Ms exposure is approximately photon limited in all seven X-ray bands for regions close to the aim point, and we predict that exposures up to ?25 Ms (0.5?2.0 keV) and ?4 Ms (2?8 keV) should remain nearly photon limited. We demonstrate that this observation does not suffer from source confusion within ?6' of the aim point, and future observations are unlikely to be source-confusion limited within ?3' of the aim point even for source densities exceeding 100,000 deg-2. These analyses directly show that Chandra can achieve significantly higher sensitivities in an efficient, nearly photon-limited manner and be largely free of source confusion. To allow consistent comparisons, we have also produced point-source catalogs for the ?1 Ms Chandra Deep Field South (CDF-S). Three hundred and twenty-six (326) X-ray sources are included in the main Chandra catalog, and an additional 42 optically bright X-ray sources are included in a lower significance Chandra catalog. We find good agreement with the photometry of the previously published CDF-S catalogs; however, we provide significantly improved positional accuracy.

THE CHANDRA DEEP FIELD-SOUTH SURVEY: 4 Ms SOURCE CATALOGS

Abstract: We present source catalogs for the 4 Ms Chandra Deep Field-South (CDF-S), which is the deepest Chandra survey to date and covers an area of 464.5 arcmin2. We provide a main Chandra source catalog, which contains 740 X-ray sources that are detected with WAVDETECT at a false-positive probability threshold of 10–5 in at least one of three X-ray bands (0.5-8 keV, full band; 0.5-2 keV, soft band; and 2-8 keV, hard band) and also satisfy a binomial-probability source-selection criterion of P 75% of the main-catalog sources are active galactic nuclei (AGNs); of the 300 new main-catalog sources, about 35% are likely normal and starburst galaxies, reflecting the rise of normal and starburst galaxies at the very faint flux levels uniquely accessible to the 4 Ms CDF-S. Near the center of the 4 Ms CDF-S (i.e., within an off-axis angle of 3'), the observed AGN and galaxy source densities have reached 9800+1300 – 1100 deg–2 and 6900+1100 – 900 deg–2, respectively. Simulations show that our main catalog is highly reliable and is reasonably complete. The mean backgrounds (corrected for vignetting and exposure-time variations) are 0.063 and 0.178 counts Ms–1 pixel–1 (for a pixel size of 0492) for the soft and hard bands, respectively; the majority of the pixels have zero background counts. The 4 Ms CDF-S reaches on-axis flux limits of 3.2 × 10–17, 9.1 × 10–18, and 5.5 × 10–17 erg cm–2 s–1 for the full, soft, and hard bands, respectively. An increase in the CDF-S exposure time by a factor of 2-2.5 would provide further significant gains and probe key unexplored discovery space.

The Swift Gamma-Ray Burst Mission

Abstract: The Swift mission, scheduled for launch in 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is a first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more than 100 bursts yr � 1 and performing detailed X-ray and UV/optical afterglow observations spanning timescales from 1 minute to several days after the burst. The objectives are to (1) determine the origin of GRBs, (2) classify GRBs and search for new types, (3) study the interaction of the ultrarelativistic outflows of GRBs with their surrounding medium, and (4) use GRBs to study the early universe out to z >10. The mission is being developed by a NASA-led international collaboration. It will carry three instruments: a newgeneration wide-field gamma-ray (15‐150 keV) detector that will detect bursts, calculate 1 0 ‐4 0 positions, and trigger autonomous spacecraft slews; a narrow-field X-ray telescope that will give 5 00 positions and perform spectroscopy in the 0.2‐10 keV band; and a narrow-field UV/optical telescope that will operate in the 170‐ 600 nm band and provide 0B3 positions and optical finding charts. Redshift determinations will be made for most bursts. In addition to the primary GRB science, the mission will perform a hard X-ray survey to a sensitivity of � 1m crab (� 2;10 � 11 ergs cm � 2 s � 1 in the 15‐150 keV band), more than an order of magnitude better than HEAO 1 A-4. A flexible data and operations system will allow rapid follow-up observations of all types of

Star Formation in the Milky Way and Nearby Galaxies

Abstract: We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star formation and gas on scales ranging from entire galaxies to individual molecular clouds.

The Swift X-ray telescope

Abstract: he Swift Gamma-Ray Explorer is designed to make prompt multiwavelength observations of gamma-ray bursts (GRBs) and GRB afterglows. The X-ray telescope (XRT) enables Swift to determine GRB positions with a few arcseconds accuracy within 100 s of the burst onset. The XRT utilizes a mirror set built for JET-X and an XMM-Newton/EPIC MOS CCD detector to provide a sensitive broad-band (0.2–10 keV) X-ray imager with effective area of > 120 cm2 at 1.5 keV, field of view of 23.6 × 23.6 arcminutes, and angular resolution of 18 arcseconds (HPD). The detection sensitivity is 2×10−14 erg cm−2 s−1 in 104 s. The instrument is designed to provide automated source detection and position reporting within 5 s of target acquisition. It can also measure the redshifts of GRBs with Fe line emission or other spectral features. The XRT operates in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return for each frame as the source intensity fades. The XRT will measure spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and will follow each burst for days or weeks.

CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey

Abstract: The Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) is designed to document the first third of galactic evolution, from z approx. 8 - 1.5. It will image > 250,000 distant galaxies using three separate cameras on the Hubble Space Tele8cope, from the mid-UV to near-IR, and will find and measure Type Ia supernovae beyond z > 1.5 to test their accuracy as standard candles for cosmology. Five premier multi-wavelength sky regions are selected, each with extensive ancillary data. The use of five widely separated fields mitigates cosmic variance and yields statistically robust and complete samples of galaxies down to a stellar mass of 10(exp 9) solar mass to z approx. 2, reaching the knee of the UV luminosity function of galaxies to z approx. 8. The survey covers approximately 800 square arc minutes and is divided into two parts. The CANDELS/Deep survey (5(sigma) point-source limit H =27.7mag) covers approx. 125 square arcminutes within GOODS-N and GOODS-S. The CANDELS/Wide survey includes GOODS and three additional fields (EGS, COSMOS, and UDS) and covers the full area to a 50(sigma) point-source limit of H ? or approx. = 27.0 mag. Together with the Hubble Ultradeep Fields, the strategy creates a three-tiered "wedding cake" approach that has proven efficient for extragalactic surveys. Data from the survey are non-proprietary and are useful for a wide variety of science investigations. In this paper, we describe the basic motivations for the survey, the CANDELS team science goals and the resulting observational requirements, the field selection and geometry, and the observing design.

A Unified, Merger-driven Model of the Origin of Starbursts, Quasars, the Cosmic X-Ray Background, Supermassive Black Holes, and Galaxy Spheroids

Abstract: We present an evolutionary model for starbursts, quasars, and spheroidal galaxies in which mergers between gas-rich galaxies drive nuclear inflows of gas, producing starbursts and feeding the buried growth of supermassive black holes (BHs) until feedback expels gas and renders a briefly visible optical quasar. The quasar lifetime and obscuring column density depend on both the instantaneous and peak quasar luminosity, and we determine this dependence using a large set of galaxy merger simulations varying galaxy properties, orbital geometry, and gas physics. We use these fits to deconvolve observed quasar luminosity functions and obtain the evolution of the formation rate of quasars with peak luminosity, (Lpeak, z). Quasars spend extended periods at luminosities well below peak, so (Lpeak) has a maximum corresponding to the break in the observed luminosity function. From (Lpeak) and our simulations, we obtain self-consistent hard and soft X-ray and optical luminosity functions and predict many observables at multiple redshifts, including column density distributions of optical and X-ray samples, the luminosity function of broad-line quasars in X-ray samples and broad-line fraction versus luminosity, active BH mass functions, the distribution of Eddington ratios, the mass function of relic BHs and total BH mass density, and the cosmic X-ray background. In every case, our predictions agree well with observed estimates, without invoking ad hoc assumptions about source properties or distributions. We provide a library of Monte Carlo realizations of our models for comparison with observations.