Stephane Paltani

Dynamics of the Lyα and C IV Emitting Gas in 3C 273

In this paper we study the variability properties of the Lyα and C IV emission lines in 3C 273 using archival International Ultraviolet Explorer observations. Our data show for the first time the existence of variability on timescales of several years. We study the spatial distribution and the velocity field of the emitting gas by performing detailed analyses on the line variability using correlations, one- and two-dimensional response functions, and principal component analysis. In both lines we find evidence for two components, one that has the dynamic properties of gas in Keplerian motion around a black hole with a mass on the order of 109 M☉, and one that is characterized by high, blueshifted velocities at large lag. There is no indication of the presence of optically thick emission medium in either the Lyα or C IV response functions. The component characterized by blueshifted velocities, which is comparatively much stronger in C IV than in Lyα, is more or less compatible with being the result of gas falling toward the central black hole with free-fall acceleration. We propose, however, that the line emission at high, blueshifted velocities is better explained in terms of entrainment of gas clouds by the jet. Therefore, this gas is probably collisionally excited as a result of heating due to the intense infrared radiation from the jet, which would explain the strength of this component in C IV relative to Lyα. This phenomenon might be a signature of disk-jet interaction.

Chandra data archive operations

The Chandra Data Archive plays a central role in the Chandra X-ray Center (CXC) that manages the operations of the Chandra X-ray Observatory. We shall give an overview of two salient aspects of the CDAs operations, as they are pertinent to the operation of any large observatory. First, in the database design it was decided to have a single observation catalog database that controls the entire life cycle of Chandra observations (as opposed to separate databases for uplink and downlink, as is common for many scientific space missions). We will discuss the pros and cons of this design choice and present some lessons learnt. Second, we shall review the complicated network that consists of Automated (pipeline) Processing, archive ingest, Verification & Validation, reprocessing, data distribution, and public release of observations. The CXC is required to deliver high-level products to its users. This is achieved through a sophisticated system of processing pipelines. However, occasional failures as well as the need to reprocess observations complicate this seemingly simple series of actions. In addition, we need to keep track of allotted and used observing time and of proprietary periods. Central to the solution is the Processing Status Database which is described in more detail in a related poster presentation.

Tracking the processing status of Chandra observations

The Chandra Data Archive has been archiving and distributing data for the Chandra X-ray Observatory and keeping observers informed of the status of their observations since shortly after launch in July 1999. Due to the complicated processing history of Chandra data, it became apparent that a database was needed to track this history on an observation by observation basis. The result is the Processing Status Database and the Chandra Observations Processing Status tool. In this paper, a description of the database design is given, followed by details of the tools which populate and display the database.