Online database of water masers in star-forming regions

Currently in the astronomy there is a trend to use large astronomical catalogs and databases in order to study different classes of the astrophysical objects. The recent development includes databases of exoplanets (EXO.MAST, Exoplanets.org), The Mikulski Archive for Space Telescopes (MAST) focused on scientific data sets in the optical, ultraviolet, and near-infrared parts of the spectrum, and others. All these databases were created with the focus on some specific phenomena, wavelength of detection or class of an astronomical object.

Water masers provide us with unique information on the properties of the interstellar medium.  However, the database of water masers is still missing to date, thus it is not possible to search across the observations of water masers available in literature. For example, while preparing the proposals for observations with single-dish and interferometric facilities, it is important to know the previous observations of some particular sources. The MaserDB project aims to solve the problem of water masers data access through variety of technological solutions, a user-friendly interface and rich opportunities of the SQL-queries. 

For creation of the maser database we use 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 in Perl/CGI language with the support of the Javascript (including AJAX technology). Online plots in the web-interface are plotted using Plotly Python Graphing Library. Simbad name resolver used for target search by source name.

Only part of the database structure is shown to illustrate the typical relations between tables:

Class I methanol maser database overview:

Ladeyschikov D.A., Bayandina O.S., Sobolev A.M. Online Database of Class I Methanol Masers // AJ. – 2019. – Vol. 158. – Iss. 6. – id. 233. – 13 pp.

Scientific use of the class I methanol maser database:

Ladeyschikov D.A., Urquhart J.S., Sobolev A.M. et al. The Physical Parameters of Clumps Associated with Class I Methanol Masers // AJ. – 2020. – Vol. 160. – Iss. 5. – id. 213. – 10 pp.

Water maser database overview: Ladeyschikov et al. (2021, in prep.)

Scientific use of water maser database: Ladeyschikov et al. (2022, in prep.)
 

The Maserdb project is collaborating with the Maser Monitoring Organization (M2O) - a global community of astronomers, observers and theorists collaborating to better understand the nature of astrophysical masers, their flaring behavior and their uses as tracers of astrophysical phenomena. Please visit the M2O web-site to get more information.

The work on water maser database is supported by Russian Science Foundation grant 20-72-00137

With MaserDB.net online tool, you can easily access the maser database and get the data that fit your needs. The web-interface consists of several key pages:

http://maserdb.net

• Ability to search for masers of different species (H2O, OH, CH3OH) using source name, coordinates, and source list.
• Displaying images in different wavelengths in search results.
• Displaying external data from astronomical catalogs related to masers studies.
   

http://maserdb.net/objects.pl

• Provides information about maser groups (objects) produced by DBSCAN alogorithm from individual maser observations. The grouping is based on combining the observations that are closer than 60 arcsecs.
• Allows to select objects using detections constraints on specific maser species.
• Allows to select objects according to user-defined criteria with SQL.
• The selection criteria constrain data using maser-related astronomical catalogs (Simbad, 2MASS, GCVS, WISE, MSX, IRAS, GLIMPSE, EGO, SDC, Akari, Herschel Hi-GAL, ATLASGAL, Bolocam GPS)

Example: Masers associated with ATLASGAL clumps

• This page is the result of object selection. It provides several tools for data analysis and data export.
• The external associated data are displayed in the same table together with maser-related data, allowing comparison. To get associated data, one should check the corresponding checkbox on the Object selection page.
• Allows filtering table by simple constraints on any column.
• Allows to plot 1D, 2D, and 3D distributions of any parameters from the results table, including associated data.
   

http://maserdb.net/user_list.pl (Example list)  

• Allows to create and share a personal source list and quickly check the masers detection information for each source.
• Automatically detect and convert sky coordinates from the input data

Example: Maser object G331.512-0.103

• This page appears when you click on a maser object.
• It provides detailed information about each object, including maser detections/non-detections (H2O, OH, SiO, CH3OH I/II), images in different wavelengths (from IR to mm and radio), associated data with maser-related astrophysical catalogs, maser spectra (images!) and descriptions, list of papers dedicated to that object.
   

The current progress in data entry for the maser database is following:

Class I methanol masers - complete at 98%.
Class II methanol masers - complete at 95%.
Water masers - ongoing (currently 89%).
Hydroxyl masers - ~70%.

The percents are calculated as the ratio between detections included in the database and total maser detections available in the literature.

The full list of papers included in the database is avalaible  online.

The following images display the spatial distribution of maser objects (groups) included in the MaserDB database. The spot size is scaled proportionally to the logarithmic peak flux density of each source.

Water maser emission is a unique phenomenon of the interstellar matter, which is currently found in star formation regions, evolved stars, and in some external galaxies. For the first time, a water maser was detected in 1969 in the direction of the Orion nebula (Cheung et al., 1969), as well as in the direction of the red supergiant VY CMa (Meeks et al., 1969). Unlike 6.7 GHz methanol masers, which are considered to be associated exclusively with the formation of massive stars, water masers are also associated with low-mass stellar objects. It was shown in Furuya et al. (2003) that water masers are primarily associated with young stellar objects (YSOs) of 0 and sometimes class I, but no water masers were found associated with class II YSOs.

The certain conditions are necessary for water maser formation - high temperature and density. Shock waves in outflows from the YSOs can create these conditions, what was shown in works Kaufman et al. (1996);  Hollenbach et al. (2013). The relationship between the water masers variability and the processes of collimation and precession of outflows from the YSO is the particular feature of water masers. Therefore, observations of water masers are often organized in a monitoring format to identify the characteristics of changes in the spectral components associated with the outflow activity from the YSO. A blind surveys of water masers in the center of the Galaxy (Caswell et al., 2011) and the galactic plane (Caswell & Breen, 2010) showed that the variability of water masers is a fairly common phenomenon. As was shown in Caswell & Breen (2010), the spatial density of the registered water masers is higher than the density of methanol and hydroxyl masers, and this occurs even in those places where methanol and hydroxyl masers are most numerous. 

Until now, work on creating a catalog of water masers has been carried out as part of the Arcetri Catalog of H2O maser sources project (Valdettaro et al., 2001). In general, this work contains information about 1000 water maser sources according to the observations up to the 2000s. 

Recently, new surveys of water masers have appeared, which significantly change our view on the number of known water maser sources. In the blind HOPS survey (Walsh et al., 2011), more than 500 water masers were detected, of which 334 were detected for the first time. In the survey of water masers in the direction of class II methanol masers (Titmarsh et al., 2014; 2016), more than 150 water maser sources were detected. Furthermore, 439 water masers were detected toward ~1600 Bolocam clumps in observations by Svoboda et al. (2016). In this regard, a revision of the water maser catalog and its statistical characteristics is required, which will be performed as part of this scientific project.

This project is dedicated to water masers in galactic star formation regions (SFRs) and aims to include at least 98% of all water maser observations in SFRs in the available literature.