Online database of astrophysical masers in star formation regions

Ladeyschikov Dmitry 1 , Olga Bayandina 2,3 , Sobolev Andrey 1

  • 1 Ural Federal University, Ekaterinburg, Russia
  • 2 Joint Institute for VLBI ERIC, Dwingeloo, Netherlands
  • 3 Astro Space Center of Lebedev Physical Institute, Moscow, Russia

Abstract

Astrophysical masers have proven themselves to be a powerful probe of the mechanisms of massive star formation, masing occurs at certain ranges of physical conditions. Thus the study of maser sites can reveal the detailed distribution of temperature and density enhancements in the host region.<br /> But while high-sensitivity observations with modern telescopes provide a significant amount of data on maser sources, its search and analysis were difficult in the absence of a general unified database. We present the first specialized online database of astrophysical masers in star-forming regions: MaserDB.net. The main goal of the project is to collect comprehensive information about all available observations of astrophysical masers in the regions of star formation. The database contains single-dish and VLBI data on both well-studied (H₂O, CH₃OH, OH) and rare maser species (e.g., H₂CO and SiO). In addition, the MaserDB database incorporates data and images from relevant infrared, submillimeter and radio catalogs, providing an extensive background for the maser data. In this review, we will present the functionality and potential of the MaserDB as a VLBI observation planning tool for the development and testing of target samples. This research is supported by the Russian Science Foundation grant 18-12-00193.

Creating the database

~~~The database was created using the PostgreSQL database management system suitable for large datasets and complex SQL-queries. The database was modified with PgSphere plugin required for work with sky coordinates. Data entry to the database was done using online Vizier archive from the Strasbourg astronomical Data Center and Optical Character Recognition (OCR) system FineReader in the cases when online data is not available. DBSCAN algorithm of Python SCIKIT-LEARN package is used for source grouping. Matching with the external datasets is done with x-match service of the Strasbourg astronomical Data Center. The online web-interface is written using Perl/CGI language with the support of the Javascript (including AJAX technology). Online plots in the web-interface are plotted using Plotly JS graphics library.

~~~Moto "the simplest solution is almost always the best" guided us in the sense of data storage, thus it is essential to not overload the database with deep decompositions to simplify the SQL-queries. For example, for the class I and class II methanol masers, the actual observational data (including non-detections) is stored in the tables met1_data and met2_data. The interferometric maser spot data for both class I and class II masers is stored in the table maser_spots to prevent overload of the main observation table. The interferometric spot table is connected to the observation tables with a simple integer identifier  obs_id.  Result of observations grouping (done with DBSCAN algorithm) is stored in the view all_objects and is recalculated with each database update. The grouping table is connected to the main observation table with grp column, identifying a source group in format of galactic coordinates "G55.371+0.185". External data (including fluxes) is stored locally in the following tables: iras, akari, bgps, atlasgal, ego and a few others. The table transitions stores the known methanol maser transitions, table papers stores the paper information (abstract, reference, data type, etc.), and table stat stores the statistics (number of detections, etc.).

Read our paper for more information:

Online Database of Class I Methanol Masers
D. A. Ladeyschikov, O. S. Bayandina, and A. M. Sobolev
2019, The Astronomical Journal, 158, 233

 

The main search page of the database web-interface.

Why we need a maser database?

~~~Currently in astronomy, there is a trend to use large astronomical catalogs and databases in order to study different classes of astrophysical objects. Databases are created with the focus on a specific phenomena, wavelength, or class of an astronomical object. However, the database of astrophysical masers was missing, and it was not possible to search across the observations of masers available in literature. Astrophysical masers provide us with unique information on the properties of the interstellar medium and are found both in galactic and extragalactic objects. The creation of a unified database solves the problem of maser data access through rich opportunities of SQL-queries.

Check it!

Please visit:

Maser Database

[maserdb.net]

~~~Maser Database is the first specialized web-interface database collecting the most up-to-date data on sources of maser emission. The maser database is equipped with a search tool allowing a unified access to the cataloged maser data, as well as to external data, including images and catalogs of well-known sky surveys. An ample functionality of statistical analysis is included to the web interface.

~~~Maser database allows one to browse spectra and individual source descriptions from literature. It will enable us to study the maser sources in detail and test their variability. More than 3300 images of class I/II methanol maser sources from 82 papers were included in the maser database, and the number is growing.

Maser sources can be selected based on any user-defined criteria, including the following parameters:

  • H2O/OH/CH3OH maser flux density at a particular frequency.
  • Maser coordinates and velocities, or distances to them.
  • IR and sub-mm fluxes of maser counterparts (detected or non-detected) from the following catalogs: 2MASS, IRAS, WISE, MSX, GLIMPSE, AKARI, BOLOCAM, and ATLASGAL.
  • Object type and characteristics based on the classification from the General Catalogue of Variable Stars [Samus et al. 2017], Extended Green Objects catalog [Cyganowski et al. 2008], and the SIMBAD database.
  • Physical parameters of ~8000 dust clumps from Urquhart et al. (2018).

Combination of the described data in one single database provides a unique opportunity to create a user-defined source list and study the maser characteristics depending on the associated IR and sub-mm data.

Test it online here!

The first scientific results

Class I methanol masers vs. ATLASGAL clumps

~~~Methanol maser emission is one of the features of star-forming regions. In early studies of Batrla et al. (1987) and Menten et al. (1991), two classes of methanol masers were empirically distinguished. While class II masers are pumped by infrared radiation of dust heated by young stars (Sobolev et al. 2005, Cragg et al. 2005); class I masers occur as a result of collisional-radiative pumping (Sobolev et al. 2007), and usually indicate the presence of gas compressed by a shock wave

~~~The maser database was used to study the physical parameters of ATLASGAL dust clumps associated with class I methanol masers.  Analysis of the clumps with detected class I methanol masers and comparing them with other clumps lead us to the conclusion that maser-associated clumps have some preferred regions in the physical parameters space. Masers tend to arise in more luminous clumps with higher temperatures and densities than the whole sample of the ATLASGAL clumps.

Distribution of ATLASGAL clump physical parameters for tree samples: all clumps, clumps associated with the 44 GHz class I methanol masers (green dots), and clumps associated with the 95 GHz class I methanol masers (red dots).  Redline in each plot reveal possible selection criteria for ATLASGAL sources with class I methanol masers.

~~~The result is in good agrement with the class I methanol pumping models. It is known that this type of masers occurs in shocked material, and clumps affected by the shock waves have higher average temperatures and densities (as well as luminosities). Clumps with higher luminosity have a higher column density, which increases the probability of acquiring high methanol column density in the shocked region, which is necessary to produce bright masers.

The results of this study are currently in publication,
check our upcoming paper:

The physical parameters of clumps associated with class I methanol masers
D. Ladeyschikov, J. S. Urquhart, A. Sobolev, S. Breen, O. Bayandina
2020, The Astronomical Journal, in review