Andrew J. Pickles

A Stellar Spectral Flux Library: 1150-25000 A ˚

A stellar spectral flux library of wide spectral coverage and an example of its application are presented. The new library consists of 131 flux-calibrated spectra, encompassing all normal spectral types and luminosity classes at solar abundance, and metal-weak and metal-rich F-K dwarf and G-K giant components. Each library spectrum was formed by combining data from several sources overlapping in wavelength coverage. The SIMBAD database, measured colors, and line strengths were used to check that each input component has closely similar stellar type. The library has complete spectral coverage from 1150 to 10620 Afor all components and to 25000 Afor about half of them, mainly later types of solar abundance. Missing spectral coverage in the infrared currently consists of a smooth energy distribution formed from standard colors for the relevant types. The library is designed to permit inclusion of additional digital spectra, particularly of non-solar abundance stars in the infrared, as they become available. The library spectra are each given as Fl versus l, from 1150 to 25000 Ain steps of 5 A ˚. A program to combine the library spectra in the ratios appropriate to a selected isochrone is described and an example of a spectral component signature of a composite population of solar age and metallicity is illustrated. The library spectra and associated tables are available as text files by remote electronic access.

The Palomar Transient Factory: System Overview, Performance, and First Results

The Palomar Transient Factory (PTF) is a fully-automated, wide-field survey aimed at a systematic exploration of the optical transient sky. The transient survey is performed using a new 8.1 square degree camera installed on the 48 inch Samuel Oschin telescope at Palomar Observatory; colors and light curves for detected transients are obtained with the automated Palomar 60 inch telescope. PTF uses 80% of the 1.2 m and 50% of the 1.5 m telescope time. With an exposure of 60 s the survey reaches a depth of m_(g′) ≈ 21.3 and m_R ≈ 20.6 (5σ, median seeing). Four major experiments are planned for the five-year project: (1) a 5 day cadence supernova search; (2) a rapid transient search with cadences between 90 s and 1 day; (3) a search for eclipsing binaries and transiting planets in Orion; and (4) a 3π sr deep H-alpha survey. PTF provides automatic, real-time transient classification and follow-up, as well as a database including every source detected in each frame. This paper summarizes the PTF project, including several months of on-sky performance tests of the new survey camera, the observing plans, and the data reduction strategy. We conclude by detailing the first 51 PTF optical transient detections, found in commissioning data.

OBSERVATIONS OF THE OH AIRGLOW EMISSION

The OH airglow emission in the J- and H-bands was observed for the purpose of determining the line widths, the precise wavelengths of individual lines, and also the continuum emission level between lines. The lines were not resolved with a resolving power of about 17000. Wavelengths and intensities were measured for approximately 120 lines from 1.1 to 1.8 microns. The continuum emission intensity was also measured on a dark night and was as low as 590 photons s-1m-2 arcsec-2 um-1 at 1.665 um. The level is about one fiftieth the average of the OH airglow emission in the H-band.

Deep Near-Infrared Observations of the W3 Main Star-forming Region

We present a deep JHKs-band imaging survey of the W3 Main star-forming region, using the near-infrared camera SIRIUS mounted on the University of Hawaii 2.2 m telescope. The near-infrared survey covers an area of ~24 arcmin2 with 10 σ limiting magnitudes of ~19.0, 18.1, and 17.3 in the J, H, and Ks bands, respectively. We construct JHK color-color and J versus J-H and K versus H-K color-magnitude diagrams to identify young stellar objects and estimate their masses. Based on these color-color and color-magnitude diagrams, a rich population of young stellar objects is identified that is associated with the W3 Main region. A large number of previously unreported red sources (H-K > 2) have also been detected around W3 Main. We argue that these red stars are most probably pre-main-sequence stars with intrinsic color excesses. We find that the slope of the Ks-band luminosity function (KLF) of W3 Main is lower than the typical values reported for young embedded clusters. The derived slope of the KLF is the same as that found in 1996 by Megeath and coworkers, from which analysis indicated that the W3 Main region has an age in the range of 0.3-1 Myr. Based on the comparison between models of pre-main-sequence stars and the observed color-magnitude diagram, we find that the stellar population in W3 Main is primarily composed of low-mass pre-main-sequence stars. We also report the detection of isolated young stars with large infrared excesses that are most probably in their earliest evolutionary phases.

The Palomar Transient Factory photometric catalog 1.0

We constructed a photometrically calibrated catalog of non-variable sources from the Palomar Transient Factory (PTF) observations. The first version of this catalog presented here, the PTF photometric catalog 1.0, contains calibrated R_PTF-filter magnitudes for ≈2.1 × 10^7 sources brighter than magnitude 19, over an area of ≈11,233 deg^2. The magnitudes are provided in the PTF photometric system, and the color of a source is required in order to convert these magnitudes into other magnitude systems. We estimate that the magnitudes in this catalog have a typical accuracy of about 0.02 mag with respect to magnitudes from the Sloan Digital Sky Survey. The median repeatability of our catalog’s magnitudes for stars between 15 and 16 mag, is about 0.01 mag and it is over 0.03 mag for 95% of the sources in this magnitude range. The main goal of this catalog is to provide reference magnitudes for photometric calibration of visible light observations. Subsequent versions of this catalog, which will be published incrementally online, will be extended to cover a larger sky area and will also include g_PTF-filter magnitudes, as well as variability and proper-motion information.

Photometric Observations Using Orthogonal Transfer CCDs

Orthogonal transfer CCDs (OTCCDs) were developed to compensate for real-time image motion, essentially providing tip/tilt corrections without additional optics or moving parts. Because of the complex gate structures of OTCCDs, their ability to provide high-precision photometric observations and their use as high- speed photometers were unclear. We detail new observations obtained with the OPTIC camera at the University of Hawaiis 2.2 m telescope on Mauna Kea that explore both of these areas. We find that OTCCDs provide equally good results in terms of typical time-series differential photometry (compared with typical CCDs) and that their high-speed photometric application is superb. Using point-spread function-shaping techniques, we obtained time-series photometric observations with precisions of 660 mmag per 180 s integration. Extending this technique to very bright stars, the potential to reach differential precisions near 10 per exposure is 5

Sequential Star Formation in A Cometary Globule (BRC37) of IC1396

We have carried out near-IR/optical observations to examine star formation toward a bright-rimmed cometary globule (BRC37) facing the exciting star(s) of an H II region (IC1396) containing an IRAS source, which is considered to be an intermediate-mass protostar. With slitless spectroscopy we detected ten Hα emission stars around the globule, six of which are near the tip of the globule and are aligned along the direction to the exciting stars. There is evidence that this alignment was originally toward an O9.5 star, but has evolved to align toward a younger O6 star when that formed. Near-IR and optical photometry suggests that four of these six stars are low-mass young stellar objects (YSOs) with masses of ~0.4 M ☉. Their estimated ages of ~1 Myr indicate that they were formed at the tip in advance of the formation of the IRAS source. Therefore, it is likely that sequential star formation has been taking place along the direction from the exciting stars toward the IRAS source, due to the UV impact of the exciting star(s). Interestingly, one faint, Hα emission star, which is the closest to the exciting star(s), seems to be a young brown dwarf that was formed by the UV impact in advance of the formation of other YSOs at the tip.

Evolution of Elliptical Galaxies at z * 1 Revealed from a Large, Multicolor Sample of Extremely Red Objects

We studied the evolution of elliptical galaxies atz 1 using a sample of 247 Extremely Red Objects (EROs) with R − Ks ≥ 3.35 (AB) and Ks ≤ 22.1 (AB) constructed from BV R izJHK s multicolor data of a 114arcmin 2 area in the Subaru/XMM-Newton Deep Field taken with the Subaru Telescope and the UH 2.2m telescope. By fitting template spectra of old galaxies (OGs) and young, dusty starbursts (DSs) to the multicolor data, we classified EROs into these two classes and estimated their redshifts. We found that 58% of the EROs in our sample belong to the OG class and that these OGs have a wide range of colors at any redshift. We derived rest-frame B-band luminosity functions of OGs in our sample at z = 1-1. 5a nd 1.5-2.5, and found that the number density of galaxies obeying passive evolution drops at z 1.5 by a factor of three or more. The spatial correlation length of OGs is estimated to be r0 8 h −1 Mpc, which is comparable to, or larger than, those of present-day early-type galaxies of similar luminosities. We also discussed properties of DSs in our data.

The University of Hawaii 2.2 Meter Fast Tip‐Tilt Secondary System

Using a new f/31 secondary on a tip-tilt platform, we have built an image-stabilization system which has been used regularly for astronomical imaging and spectroscopy on the University of Hawaii 2.2 m telescope. Diffraction-limited cores of stellar point-spread functions are achieved in near-infrared imaging, with Strehl ratios as high as 0.47. K-band images with 03 FWHM resolution (without deconvolution) are routinely obtained. The construction, operation, and capability of the current system are described, a summary of recent scientific findings is presented, and future improvements are outlined.

Fast and robust pointing and tracking using a second-generation star tracker

Second generation star trackers work by taking wide-angle optical pictures of star fields, correlating the image against a star catalogue in ROM, centroiding many stars to derive an accurate position and orientation. This paper describes a miniature instrument, fast and lightweight, including database and search engine. It can be attached to any telescope to deliver an accurate absolute attitude reference via a serial line. It is independent of encoders or control system, and works whenever it can see the sky. Position update rates in the range of 1 to 5 Hz enable closed-loop operations. The paper describes the instrument operational principles, and its application as an attitude reference unit for a telescope. Actual data obtained at the University of Hawaiis 0.6-m telescope are presented, and their utility for correcting mechanical alignment discussed. The system has great potential as a positioner and guider for (i) remotely operated optical telescopes, (ii) IR telescopes operating in dark clouds, and (iii) radio telescopes. Other application recommendations and the performance estimates are given.