Russell B. Makidon

WFPC2 Observations of the Hubble Deep Field South

The Hubble Deep Field South (HDF-S) observations targeted a high Galactic latitude field near QSO J2233-606. We present Wide Field Planetary Camera 2 observations of the field in four wide bandpasses centered at roughly 300, 450, 606, and 814 nm. Observations, data reduction procedures, and noise properties of the final images are discussed in detail. A catalog of sources is presented, and the number counts and color distributions of the galaxies are compared with a new catalog of the original Hubble Deep Field (HDF-N) that has been constructed in an identical manner. The two fields are qualitatively similar, with the galaxy number counts for the two fields agreeing to within 20%. The HDF-S has more candidate Lyman break galaxies at z > 2 than the HDF-N. The star formation rate per unit volume computed from the HDF-S, based on the UV luminosity of high-redshift candidates, is a factor of 1.9 higher than from the HDF-N at z ~ 2.7, and a factor of 1.3 higher at z ~ 4.

THE STRUCTURE OF HIGH STREHL RATIO POINT-SPREAD FUNCTIONS

We describe the symmetries present in the point-spread function (PSF) of an optical system either located in space or corrected by an adaptive optics (AO) system to Strehl ratios of about 70% and higher. We present a formalism for expanding the PSF to arbitrary order in terms of powers of the Fourier transform of the residual phase error over an arbitrarily shaped and apodized entrance aperture. For traditional unapodized apertures at high Strehl ratios, bright speckles pinned to the bright Airy rings are part of an antisymmetric perturbation of the perfect PSF, arising from the term that is first order in the residual phase error. There are two symmetric second-degree terms. One is negative at the center and, like the first-order term, is modulated

Ground-based Coronagraphy with High-order Adaptive Optics

We summarize the theory of coronagraphic optics and identify a dimensionless —ne-tuning parameter, F, which we use to describe the Lyot stop size in the natural units of the coronagraphic optical train and the observing wavelength. We then present simulations of coronagraphs matched to adaptive optics (AO) systems on the Calypso 1.2 m, Palomar Hale 5 m, and Gemini 8 m telescopes under various atmospheric conditions and identify useful parameter ranges for AO coronagraphy on these telescopes. Our simulations employ a tapered, high-pass —lter in spatial frequency space to mimic the action of adaptive wave front correction. We test the validity of this representation of AO correction by comparing our simulations with recent K-band data from the 241 channel Palomar Hale AO system and its dedicated Palomar High Angular Resolution Observer (PHARO) science camera in coronagraphic mode. Our choice of monochromatic modeling enables us to distinguish between underlying halo suppression and ★ b)

The Hubble Deep Field South: Formulation of the Observing Campaign

Deep, multiband observations of high Galactic latitude fields are an essential tool for studying topics ranging from Galactic structure to extragalactic background radiation. The Hubble Deep Field (HDF-N) observations obtained in 1995 December established a standard for such narrow, deep surveys. The field has been extensively analyzed by a variety of groups and has been widely studied with imaging and spectroscopy over wavelengths ranging from 10-3 to 2 × 105 μm. We describe here a second deep field campaign (HDF-S), this time in the southern hemisphere, undertaken by the Hubble Space Telescope (HST) in 1998 October in a program very similar to the northern Hubble Deep Field. Imaging and spectroscopy of three adjacent fields in the southern continuous viewing zone were obtained simultaneously for 150 orbits, and a mosaic of flanking fields was imaged for 27 additional orbits. Two important features of the HDF-S distinguish it from the HDF-N: the campaign included parallel observations by the three main HST instruments—WFPC2, STIS, and NICMOS—and the HDF-S location was selected to place a bright z = 2.24 quasar in the STIS field of view. The HDF-S observations consist of WFPC2 images in filters close to U, B, V, and I, a deep STIS image of the field surrounding the quasar, spectroscopy of the quasar with STIS from 1150 to 3560 A, and deep imaging of an adjacent field with NICMOS camera 3 at 1.1, 1.6, and 2.2 μm. All of the HDF-S data were fully reduced and made publicly available within 2 months of the observations, and we describe here the selection of the fields and the observing strategy that was employed. Detailed descriptions of the data and the reduction techniques for each field, together with the corresponding source catalogs, appear in separate papers.

Resolving OB Systems in the Carina Nebula with the Hubble Space Telescope Fine Guidance Sensor

We observed 23 OB stars in the Carina Nebula (NGC 3372) with the Hubble Space Telescopes Fine Guidance Sensor 1r (FGS1r) in its high angular resolution mode. Five of these OB stars are newly resolved binaries with projected separations ranging from 0015 to 0352 (37 to 880 AU at a distance of 2.5 kpc), and V-band magnitude differences ranging from 0.9 to 2.8. The most important astrophysical result is the unexpected resolution of the prototype O2 If* star HD 93129A as a 55 milliarcsecond (mas) double with a ΔmV of 0.9. This object has served as a spectroscopic benchmark for the analysis of the most massive hot stars and their winds on the prior assumption that it is a single star. This discovery supports the interpretation of recent radio and X-ray observations as evidence of colliding-wind phenomena in HD 93129A. Another interesting result is the determination of an upper limit of about 35 AU for the projected separation of the binary pairs in the hierarchical double spectroscopic binary HD 93206. The high incidence of resolved binaries provides motivation for a more thorough, statistically meaningful study of multiplicity among the most massive stars in the young ionizing clusters of the nebula to obtain a complete sample of the long-period systems that have evaded spectroscopic detection. However, considering that the nine spectroscopic binaries with accurate orbits in the Carina Nebula have orbital dimensions 1 AU, which at a distance of 2.5 kpc subtends an angle of only 0.4 mas, well below the 10 mas angular resolution of FGS1r, there remains a significant range of orbital periods and separations over which it is very difficult to detect multiplicity in the nebula with currently available instruments.

Is that really your Strehl ratio

Strehl ratio is the most commonly used metric for adaptive optics (AO) performance. It is also the most misused metric. Every Strehl ratio measurement algorithm has subtle differences that result in different measured values. This creates problems when comparing different measurements of the same AO system and even more problems when trying to compare results from different systems. To determine how much the various algorithm difference actually impacted the measured values, we created a series of simulated point spread functions (PSF). The simulated PSFs were then sent around to the various members of the project who then measured the Strehl ratio. The measurements were done blindly, with no knowledge of the true Strehl ratio. We then compared the various measurements to the truth values. Each measurement cycle turned up impacts which were further investigated in the next cycle. We present the results of our comparisons showing the scatter in measured Strehl ratios and our best recommendations for computing an accurate Strehl ratio.

THE LYOT PROJECT DIRECT IMAGING SURVEY OF SUBSTELLAR COMPANIONS: STATISTICAL ANALYSIS AND INFORMATION FROM NONDETECTIONS

The Lyot project used an optimized Lyot coronagraph with extreme adaptive optics at the 3.63 m Advanced Electro-Optical System telescope to observe 86 stars from 2004 to 2007. In this paper, we give an overview of the survey results and a statistical analysis of the observed nondetections around 58 of our targets to place constraints on the population of substellar companions to nearby stars. The observations did not detect any companion in the substellar regime. Since null results can be as important as detections, we analyzed each observation to determine the characteristics of the companions that can be ruled out. For this purpose, we use a Monte Carlo approach to produce artificial companions and determine their detectability by comparison with the sensitivity curve for each star. All the non-detection results are combined using a Bayesian approach and we provide upper limits on the population of giant exoplanets and brown dwarfs for this sample of stars. Our nondetections confirm the rarity of brown dwarfs around solar-like stars and we constrain the frequency of massive substellar companions (M>40 M_J) at orbital separation between and 10 and 50 AU to be ≲20%.

The Lyot project: toward exoplanet imaging and spectroscopy

Among the adaptive optics systems available to astronomers, the US Air Force Advanced Electro-Optical System (AEOS) is unique because it delivers very high order wave front correction. The Lyot Project includes the construction and installation of the world’s first diffraction-limited, optimized coronagraph that exploits the full astronomical potential of AEOS and represents a critical step toward the long-term goal of directly imaging and studying extrasolar planets (a.k.a. “exoplanets”). We provide an update on the Project, whose coronagraph saw first light in March 2004. The coronagraph is operating at least as well as predicted by simulations, and a survey of nearby stars has begun.

The Early Angular Momentum History of Low-Mass Stars:Evidence for a Regulation Mechanism

We examine the early angular momentum history of stars in young clusters via 197 photometric periods in fields flanking the Orion Nebula cluster (ONC), 81 photometric periods in NGC 2264, and 202 measurements of v sin i in the ONC itself. We show that pre–main-sequence stars spanning an age range from 0.1 to 3 Myr do not appear to conserve stellar angular momentum as they evolve down their convective tracks, but instead preserve the same range of periods even though they have contracted by about a factor of 3. This result seems to require a mechanism that regulates the angular velocities of young stars. We discuss several candidate mechanisms. The most plausible appears to be disk locking, though most of our stars do not have IC-Ks excesses suggestive of disks. However, a decisive test of this hypothesis requires a more sensitive diagnostic than the IC-Ks excesses used here.

CHANDRA X-RAY OBSERVATIONS OF YOUNG CLUSTERS. I. NGC 2264 DATA

We present results of a Chandra observation of a field in NGC 2264. The observations were taken with the ACIS-I camera with an exposure time of 48.1 ks. We present a catalog of 263 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. We found 41 variable sources, 14 of which have a flarelike light curve, and two of which have a pattern of a steady increase or decrease over a 10 hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being pre–main-sequence stars with ages younger than 3 Myr.