Splinter Meeting "G": E-Science & Virtual Observatory

The plate archive in Bonn (”Sammlung Historischer Himmelsaufnahmen”, [SHH]) is a collection of some 15.000 photographic plates taken in Bonn, Go ̈ttingen and Hoher List observatory from 1899 to 1990. Moreover there exist small numbers of plates from other observatories like Boyden, ESO and Rozhen. We have started to do an inventory of all plates, which at the moment are distributed over several rooms in our institute. At the same time we are performing astrometric and photometric tests of the plates taken with the different telescopes. Our general purpose is, to use the plates for science, didactic (work with students from schools) and for public outreach.

• We started a new determination of the absolute proper motions of 35 open star clusters with an accuracy of 0.3 mas/yr. All plates were scanned in four orientations with an EPSON 4990 in order to avoid systematic errors. The proper motions were related to 80 Tycho2 stars. Here we present the first results of four star clusters.
• In January, June and October students from schools are working 14 to 21 days in our institute. They do exercises and little research with scans of the plates. As a first result we have published light curves of Mira stars in the BAV. The final goal is a catalogue of historical photometric data of variable stars with respect to Gaia photometry.
• Digitized observations were used for topics for public talks (e.g. Messier 42). Moreover we are involved in art-projects using the old plates. A first exhibition was performed in November 2013 and other will follow in 2015.

The Astronomical Institute of the Ruhr-University Bochum, the first for the new Universities founded in Germany in the 60ties and 70ties, is maybe not a very natural place to expect even a modest collection of photographic plates. Still, over the first ~20 years of the history of AIRUB, several sets of old plates and a sizeable number of plates from ESO and other observatories where brought to Bochum as part of various science programs.

After moving the plates to a single storage place in the institute we now started compiling a full inventory. The collection includes e.g. the plate collection of the Bochum Comet Halley campaign at La Silla, and apparently a part of the Bolivia objectiv prism survey. Already, several other promising data sets where found by us, too. As a result, we started experiments with plate scanning and used M. Gefferts scanning hardware at AIfA Bonn (the site of the ``Sammlung Historischer Himmelsaufnahmen``).

First science projects focus on long-term variability, which is also linked to already ongoing programs at Bochum on the physics and evolution of very massive stars. We started to look at Magellanic Cloud plates in the Bamberg collection in connection with our Magellanic Cloud photometric survey MCSF, and have already first results from photometry on historic plates and new CCD data of the Tautenburg 2m telescope on massive stars in M33 (Burggraf et al. 2014) and M31.

Regular observations of star fields are the common procedure to search for variable stars. In former times these observations have been done mostly using photographic emulsions, usually applied onto glas plates. Many collections of such plates are stored within German observatories; e.g. the Dr. Remeis-Observatory at Bamberg accomodates about 40.000. The oldest photographic plates stored at the Bamberg archive are from the early 1910s.

These plates are not only interesting for a historian, but also from a scientist's point of view they are still an important tool in order to hunt e.g. for long time variable or high proper motion stars, or to better calculate the orbits of asteroids and comets. The study of the predecessors of eruptive, cataclysmic or explosive variable stars, and other optical transients, is also only possible using these (very) old observations.

However, some of the photographic emulsions already begin to decompose and dissolve from their glas plates. The best way to preserve these observations, and to give the community acces to the data, is digitization. In collaboration of the Leibnitz astrophysical institute at Potsdam, the Hamburg observatory at Hamburg, and the Remeis-Observatory at Bamberg, a DFG funded project was initiated in 2012 in order to digitize all photographic plates stored at each institute, and integrate the resulting data into the Virtual Observatory.

We report about the second year of operation at the Dr. Remeis-Observatory at Bamberg.

Photographic plate collections worldwide contain large amounts of unexplored data on the variable sky. The challenge is to make these data accessible for research use, which means digitising plates and logbooks, extracting sources from images, calibrating extracted data, and finally, publishing the data in searchable form.

This talk will cover our experience from creating the APPLAUSE database that contains digitised photographic data from the Hamburg, Bamberg and Potsdam archives. A major issue is the heterogeneity of plate collections that makes it difficult to store all relevant metadata uniformly in a database and FITS image files. We have developed a Python software package, PyPlate, that handles metadata parsing and storing, extraction of sources from digital images, and calibration of celestial coordinates for all extracted sources. Methods for calibrating stellar magnitudes and spectra are being developed.

In astronomy, new approaches to process and analyze the exponentially increasing amount of data are inevitable. While classical approaches (e.g. template fitting) are fine for objects of well-known classes, alternative techniques have to be developed to determine those that do not fit. Therefore a classification scheme should be based on individual properties instead of fitting to a global model and therefore loose valuable information. An important issue when dealing with large data sets is the outlier detection which at the moment is often treated problem-orientated.

In this paper we present a method to statistically estimate the redshift $z$ based on a similarity approach. This allows us to determine redshifts in spectra in emission as well as in absorption without using any predefined model. Additionally we show how an estimate of the redshift based on single features is possible. As a consequence we are e.g. able to filter objects which show multiple redshift components. We propose to apply this general method to all similar problems in order to identify objects where traditional approaches fail.

The redshift estimation is performed by comparing predefined regions in the spectra and applying a $k$ nearest neighbor regression model for every predefined emission and absorption region, individually.

We estimated a redshift for more than 50% of the analyzed 16,000 spectra of our reference and test sample. The redshift estimate yields a precision for every individually tested feature that is comparable with the overall precision of the redshifts of SDSS. In 14 spectra we find a significant shift between emission and absorption or emission and emission lines. The results show already the immense power of this simple machine learning approach for investigating huge databases such as the SDSS.

The Astropy Project is a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages. In addition an ecosystem of Astropy affiliated packages is growing, some of which are planned for inclusion in the Astropy core when they are matured, some with specialised functionality will remain as separate repositories.

I will give an overview of the features and implementation of the Astropy package, focusing on parts that are more generally useful for scientists and engineers (e.g. astropy.units and astropy.modeling) and highlight recent developments in the core and affiliated packages.

Programmatic -- as opposed to client-based -- access to the facilities of the Virtual Observatory's has so far been reserved to experts or one-off curl-based hacks. With astropy, its affiliated packages and some python programming, it is now becoming accessible to the average, Python-speaking astronomer, too. In this talk, we will briefly present some recipies that can be re-used to quickly create smart, interactive astronomy applications that seamlessly integrate standard clients, remote services, and custom logic provided by the local astronomer.

tbd.