The Chandra X-Ray Observatory's Radiation Environment and the AP-8/AE-8 Model

The Chandra X-ray Observatory (CXO) was launched on July 23, 1999 and reached its final orbit on August 7, 1999. The CXO is in a highly elliptical orbit, approximately 140,000 km x 10,000 km, and has a period of approximately 63.5 hours (~ 2.65 days). It transits the Earth's Van Allen belts once per orbit during which no science observations can be performed due to the high radiation environment. The Chandra X-ray Observatory Center (CXC) currently uses the National Space Science Data Center's ``near Earth'' AP-8/AE-8 radiation belt model to predict the start and end times of passage through the radiation belts. However, our scheduling software uses only a simple dipole model of the Earth's magnetic field. The resulting B, L magnetic coordinates, do not always give sufficiently accurate predictions of the start and end times of transit of the Van Allen belts. We show this by comparing to the data from Chandra's on-board radiation monitor, the EPHIN (Electron, Proton, Helium Instrument particle detector) instrument. We present evidence that demonstrates this mis-timing of the outer electron radiation belt as well as data that also demonstrate the significant variablity of one radiation belt transit to the next as experienced by the CXO. We also present an explanation for why the dipole implementation of the AP-8/AE-8 model is not ideally suited for the CXO. Lastly, we provide a brief discussion of our on-going efforts to identify a model that accounts for radiation belt variability, geometry, and one that can be used for observation scheduling purposes.Comment: 12 pgs, 6 figs, for SPIE 4012 (Paper 76

The Hard X-Ray View of Reflection, Absorption, and the Disk-Jet Connection in the Radio-Loud AGN 3C 33

We present results from Suzaku and Swift observations of the nearby radio galaxy 3C 33, and investigate the nature of absorption, reflection, and jet production in this source. We model the 0.5-100 keV nuclear continuum with a power law that is transmitted either through one or more layers of pc-scale neutral material, or through a modestly ionized pc-scale obscurer. The standard signatures of reflection from a neutral accretion disk are absent in 3C 33: there is no evidence of a relativistically blurred Fe K$\alpha$ emission line, and no Compton reflection hump above 10 keV. We find the upper limit to the neutral reflection fraction is R<0.41 for an e-folding energy of 1 GeV. We observe a narrow, neutral Fe K$\alpha$ line, which is likely to originate at least 2,000 R_s from the black hole. We show that the weakness of reflection features in 3C 33 is consistent with two interpretations: either the inner accretion flow is highly ionized, or the black-hole spin configuration is retrograde with respect to the accreting material.Comment: 12 pages, 11 figures, 4 tables. Accepted for publication in Ap

Optical Spectroscopy Of X-Ray Sources In The Extended Chandra Deep Field South

We present the first results of our optical spectroscopy program aimed to provide redshifts and identifications for the X-ray sources in the Extended Chandra Deep Field South. A total of 339 sources were targeted using the IMACS spectrograph at the Magellan telescopes and the VIMOS spectrograph at the VLT. We measured redshifts for 186 X-ray sources, including archival data and a literature search. We find that the active galactic nucleus (AGN) host galaxies have on average redder rest-frame optical colors than nonactive galaxies, and that they live mostly in the "green valley." The dependence of the fraction of AGNs that are obscured on both luminosity and redshift is confirmed at high significance and the observed AGN spatial density is compared with the expectations from existing luminosity functions. These AGNs show a significant difference in the mid-IR to X-ray flux ratio for obscured and unobscured AGNs, which can be explained by the effects of dust self-absorption on the former. This difference is larger for lower luminosity sources, which is consistent with the dust opening angle depending on AGN luminosity.National Aeronautics and Space Administration PF8-90055, NAS8-03060NSF AST0407295Spitzer JPL RSA1288440Natural Science and Engineering Research Council of Canada (NSERC)National Academy of SciencesNASA/INTEGRAL NNG05GM79GAstronom

The Flight Spectral Response of the ACIS Instrument

We discuss the flight calibration of the spectral response of the Advanced CCD Imaging Spectrometer (ACIS) on-board the Chandra X-ray Observatory (CXO). The spectral resolution and sensitivity of the ACIS instrument have both been evolving over the course of the mission. The spectral resolution of the frontside-illuminated (FI) CCDs changed dramatically in the first month of the mission due to radiation damage. Since that time, the spectral resolution of the FI CCDs and the backside-illuminated (BI) CCDs have evolved gradually with time. We demonstrate the efficacy of charge-transfer inefficiency (CTI) correction algorithms which recover some of the lost performance. The detection efficiency of the ACIS instrument has been declining throughout the mission, presumably due to a layer of contamination building up on the filter and/or CCDs. We present a characterization of the energy dependence of the excess absorption and demonstrate software which models the time dependence of the absorption from energies of 0.4 keV and up. The spectral redistribution function and the detection efficiency are well-characterized at energies from 1.5 to 8.0 keV. The calibration at energies below 1.5 keV is challenging because of the lack of strong lines in the calibration source and also because of the inherent non-linear dependence with energy of the CTI and the absorption by the contamination layer. We have been using data from celestial sources with relatively simple spectra to determine the quality of the calibration below 1.5 keV. The analysis of these observations demonstrate that the CTI correction recovers a significant fraction of the spectral resolution of the FI CCDs and the models of the time-dependent absorption result in consistent measurements of the flux at low energies for data from a BI (S3) CCD.Comment: 12 pages, 15 figures, SPIE style file, To appear in "Astronomical Telescopes and Instrumentation 2002" (SPIE Conference Proceedings), eds. J.E. Truemper and H.D. Tananbau

The UV colours of high-redshift early-type galaxies: evidence for recent star formation and stellar mass assembly over the last 8 billion years

We combine deep UBVRIzJK photometry from the Multiwavelength Survey by Yale-Chile (MUSYC) with redshifts from the COMBO-17 survey to perform a large-scale study of the rest-frame ultraviolet (UV) properties of 674 high-redshift (0.5<z<1) early-type galaxies, drawn from the Extended Chandra Deep Field South (E-CDFS). Galaxy morphologies are determined through visual inspection of Hubble Space Telescope (HST) images taken from the GEMS survey. We harness the sensitivity of the UV to young (<1 Gyr old) stars to quantify the recent star formation history of early-type galaxies across a range of luminosities (-23.5 < M(V) < -18). Comparisons to simple stellar populations forming at high redshift indicate that only ~1.1 percent of early-types in this sample are consistent with purely passive ageing since z=2. Parametrising the recent star formation (RSF) in terms of the mass fraction of stars less than a Gyr old, we find that the early-type population as a whole shows a typical RSF between 5 and 13% in the redshift range 0.5<z<1. Early-types on the UV red sequence show RSF values less than 5% while the reddest early-types are virtually quiescent with RSF values of ~1%. We find compelling evidence that early-types of all luminosities form stars over the lifetime of the Universe, although the bulk of their star formation is already complete at high redshift. This tail-end of star formation is measurable and not negligible, with luminous (-23<M(V)<-20.5) early-types potentially forming 10-15% of their mass since z=1, with their less luminous (M(V)>-20.5) counterparts potentially forming 30-60 percent of their mass in the same redshift range. (abridged)Comment: Submitted to MNRA

A brief review of Agada Yoga and its utility in treatment

Ayurveda is a conventional medical system with origins in the Indian subcontinent. There are eight main medical specialties in it. One of the specialist branches of Ayurveda, known as Agada Tantra, provides incredibly detailed knowledge regarding both living and non-living toxins, as well as how to remove them from the body. There are numerous ancient books in which we can find references of Agada Yoga. Agada Yoga are substances that are used to neutralise or deactivate the effects of toxins. Poisoning can occur through plant or animal bites such as snake bites, agricultural poisons, poisonous metals and minerals, and so on. The Agada Yoga which is mentioned in the Agada Tantra, is utilised to heal a wide range of illnesses, including poisoning cases, poisonous skin manifestations, and many systemic illnesses. These Agadas are used to treat poisoning cases and its complication. Various Agadas are mentioned in various ancient books for the treatment of toxicity. This article makes an effort to review different Agad Yogas mentioned in ayurvedic literature

A Public, K-Selected, Optical-to-Near-Infrared Catalog of the Extended Chandra Deep Field South (ECDFS) from the MUltiwavelength Survey by Yale-Chile (MUSYC)

We present a new K-selected, optical-to-near-infrared photometric catalog of the Extended Chandra Deep Field South (ECDFS), making it publicly available to the astronomical community. The dataset is founded on publicly available imaging, supplemented by original zJK imaging data obtained as part of the MUltiwavelength Survey by Yale-Chile (MUSYC). The final photometric catalog consists of photometry derived from nine band U-K imaging covering the full 0.5x0.5 sq. deg. of the ECDFS, plus H band data for approximately 80% of the field. The 5sigma flux limit for point-sources is K = 22.0 (AB). This is also the nominal completeness and reliability limit of the catalog: the empirical completeness for 21.75 < K < 22.00 is 85+%. We have verified the quality of the catalog through both internal consistency checks, and comparisons to other existing and publicly available catalogs. As well as the photometric catalog, we also present catalogs of photometric redshifts and restframe photometry derived from the ten band photometry. We have collected robust spectroscopic redshift determinations from published sources for 1966 galaxies in the catalog. Based on these sources, we have achieved a (1sigma) photometric redshift accuracy of Dz/(1+z) = 0.036, with an outlier fraction of 7.8%. Most of these outliers are X-ray sources. Finally, we describe and release a utility for interpolating restframe photometry from observed SEDs, dubbed InterRest. Particularly in concert with the wealth of already publicly available data in the ECDFS, this new MUSYC catalog provides an excellent resource for studying the changing properties of the massive galaxy population at z < 2. (Abridged)Comment: Re-submitted to ApJSS after a first referee report. 27 pages, 17 figures. MUSYC data is freely available from http://astro.yale.edu/MUSYC . Links to phot-z and restframe photometry catalogs, as well as to InterRest access and documentation, including a full walkthrough, can be found at http://www.strw.leidenuniv.nl/~ent