Database for Studying Edge-on Galaxies

Abstract—We present a database created within the project on studying edge-on galaxies. These galaxies provide a unique opportunity to study the three-dimensional distribution of the matter in galaxy disks, which is extremely important for analyzing the influence of internal and external factors on the evolution of galaxies. For the moment, extensive observed material has been accumulated on the kinematics and photometry of such galaxies. The database is designed to organize information, make it easier to visualize, and to improve works on studying this type of objects. The database combines information from previous catalogs on edge-on galaxies and data from current projects; provides access to astrometric and photometric data; carries out interconnection with other databases. The present paper describes the structure and web-access to the database: https://www.sao.ru/edgeon/.

APPENDIX

1.1 RFGC STRUCTURE

The catalog is presented as a table, following the structure of the RFGC catalog described in the original paper by Karachentsev et al. (1999):

rfgc—the galaxy identifier from RFGC catalog in the range from RFGC 0001 to RFGC 4236;

fgc—the name of the galaxy from the catalog FGC (Karachentsev et al. 1993) (FGC 0001–FGC 2573). The southern extension of the catalog contains identifiers from FGCE 0001 to FGCE 1882;

ra, dec—the right ascension and declination of the galaxy in degrees for the epoch J2000.0. The coordinates have been refined with the HyperLeda database (Makarov et al., 2014);

pa— the positional angle of the major axis of the galaxy in degrees measured from north to east;

aO, bO—the “blue” diameters of the major and minor axes of the galaxy in arc minutes in the POSS-I size system;

aE, bE—the “red” diameters of the major and minor axes of the galaxy in arc minutes in the POSS-I size system;

type—the morphological galaxy type according to the Hubble classification;

As—the asymmetry index (0—a symmetrical galaxy, 2—the pronounced asymmetry);

sb—the average surface brightness index (1—high, 4—very low);

Btot—the total apparent $B$ magnitude calculated based on the sizes, morphological type, and surface brightness type as described in the RFGC catalog;

nsat—the number of significant satellites (see description in the original RFGC catalog);

notes—the notes on galaxies;

pgc—the PGC galaxy number from the HyperLeda database (Makarov et al., 2014).

1.2 EGIS STRUCTURE

The catalog is generated based on the latest versions of Tables¹⁷ 4 and 6 from the paper by Bizyaev et al. (2014). The original tables give photometry of galaxies performed in two different ways. They have been converted into three database tables to eliminate redundancy.

1.3 egis

This table contains a list of “true” edge-on galaxies Bizyaev et al. (2014):

eon—the unique galaxy identifier from the original paper;

ra, dec—the right ascension and declination of a galaxy in degrees for the epoch J2000.0;

altname—the name of the galaxy in other catalogs;

type—the morphological type of a galaxy: Sa, Sb, Sc, Sd, or Ir;

rv—the heliocentric radial velocity in km s^–1 according to HyperLeda as listed in the original catalog Bizyaev et al. (2014).

1.4 egis_phot3d

The photometry table from the one-dimensional analysis of the brightness profiles of edge-on galaxies:

eon—the unique identifier associated with the |egis| Table;

band—the SDSS filter($gri$);

pa—the position angle of the galaxy;

h, e_h —the radial exponential scale of the galaxy disk in arc seconds and its error;

z0, e_z0—the vertical $\mathop {{\text{sech}}}\nolimits^{\text{2}}$ scale of the galaxy disk in arc seconds and its error;

sb0, e_sb0—the central surface brightness of a galaxy modified to the face-on position, in mag arcsec^–2 and its error;

grad_z0—the gradient of the vertical scale of the disk $z0$ normalized to the ratio of the scales: $\tfrac{{d{{z}_{0}}}}{{dr}}\tfrac{h}{{{{z}_{0}}}}$;

mag—the total aperture magnitude inside the bounding ellipse corrected for extinction in our Galaxy according to (Schlegel et al., 1998);

B/T—the ratio of the bulge brightness to the total luminosity of a galaxy;

fits—the indicator to the FITS file in the local archive;

ima—the indicator to the galaxy image in the given filter for visualization using the web interface.

1.5 egis_phot1d

The photometry table from the analysis of the brightness distribution of galaxies in the SDSS image in the $r$ filter (3D-Analysis):

eon—the unique identifier associated with the |egis| Table;

band—the SDSS filter. Should always be equal to ($r$);

h—the radial exponential scale of the galaxy disk in arc seconds;

z0—the vertical $\mathop {{\text{sech}}}\nolimits^{\text{2}}$ scale of the galaxy disk in arc seconds;

sb0—the central surface brightness of the galaxy modified to the face-on position, in mag arcsec².

1.6 2MFGC STRUCTURE

id—the 2MFGC identifier of a galaxy (2MFGC 00001–2MFGC 18020);

pgc—the PGC galaxy number from the HyperLeda database (Makarov et al., 2014);

ra, dec—the right ascension and declination of a galaxy in degrees for the epoch J2000.0;

r—the elliptical Kron radius in the 2MASS filter ${{K}_{s}}$. This aperture was used for photometry in all three 2MASS filters.;

Jmag—the Kron magnitude in the $J$ filter of the 2MASS survey;

Hmag—the Kron magnitude in the $H$ filter of the 2MASS survey;

Ksmag—the Kron magnitude in the ${{K}_{s}}$ filter of the 2MASS survey;

b/a—the axial ratio of a galaxy in the composite $J + H + {{K}_{s}}$ image;

b/a1—the axial ratio averaged over individual images in the $J$-, $H$-, and ${{K}_{s}}$ filters;

pa— the positional angle in the composite image measured from north N to east E;

CI—the concentration index in the $J$ filter (the ratio of the radii in which 3/4 and 1/4 of the galaxy light is concentrated).

1.7 STRUCTURE OF TABLES OF CANDIDATES FROM THE PAN-STARRS SURVEY

1.8 ps1candidate

The table gives information about edge-on galaxy candidates found in the Pan-STARRS survey. It contains the identifier of the object; its coordinates; photometric parameters obtained during primary selection, and indicators to files in the local archive.

projcell, subcell, candidate—this three-digit combination is used as the unique identifier of objects and is determined by the specific character of the image archive organization in the Pan-STARRS survey¹⁸. The pair of numbers projcell and subcell indicates the projection number in the sky and the cell number in the given division, respectively. The candidate number—candidate,—found in this image by our search algorithm for edge-on galaxies;

ra, dec—the right ascension and declination of the candidate in degrees for the J2000.0 epoch;

sma_r—the major semi-axis corresponding to the characteristic width of the Gaussian inscribed in the two-dimensional distribution of light from a galaxy in the $r$-filtered image;

ell_r—the ellipticity, ${{1 - b} \mathord{\left/ {\vphantom {{1 - b} a}} \right. \kern-0em} a}$, of the corresponding Gaussian;

pa_r—the corresponding positional angle in the image;

mag_r—the estimation of the total apparent magnitude of the object;

fits_g, fits_r, fits_i—the indicators to FITS files in the local image archive for each of the three filters;

image, contour—the color image and image with the marked outline of the candidate selection, respectively, for the convenience of viewing candidates.

1.9 ps1candidate_annvote

This table gives information on candidate classification obtained in five different artificial neural network models trained to classify edge-on galaxies:

projcell, subcell, candidate—the unique identifier of the object associated with the ps1candidate Table;

n—the number of a model used to classify a candidate;

vote—the index of conformity to edge-on galaxies obtained within the framework of the corresponding model: 0—does not match, 1—classified as an edge-on galaxy.

1.10 ps1candidate_class

This table gives information about the visual classification of candidates by the project participants. The classification process was divided into several stages, thus, the same object could be classified by the same person several times.

projcell, subcell, candidate—the unique identifier of the object associated with the ps1candidate Table;

userid—the identifier of the user who performed the classification;

date—the classification time;

workflow—the indicator of the stage, during which the identification was carried out;

class—the actual classification performed by this user during the current stage. Possible values are: good—a galaxy is almost edge-on; acceptable—a galaxy is seen at a high angle to the line of sight; unsuitable—an object is not an edge-on galaxy; wrong—a candidate is not a galaxy (a defect in the image or a combination of stars);

use—the flag of using this classification in statistics (true or false).

1.11 ps1candidate_phot

The table presents the photometry of galaxies performed by the SExtractor¹⁹ code with the images from the Pan-STARRS survey in five filters:

projcell, subcell, candidate—the unique identifier of an object associated with the ps1candidate Table;

band—the Pan-STARRS1 filter ($g$, $r$, $i$, $z$, and $y$);

ra, dec—the right ascension and declination of a candidate in degrees for the epoch J2000.0;

xima, yima—the coordinates of the barycenter of an object in the image (the parameters X_IMAGE, Y_IMAGE in SExtractor);

aima, bima, paima—the major and minor semi-axes and the positional angle of the ellipse describing the given object in the image (the parameters A_IMAGE, B_IMAGE, THETA_IMAGE in SExtractor);

a, e_a—the semi-major axis of an object in the sky and its error in arc seconds (the parameters A_IMAGE, ERRA_IMAGE);

b, e_b—the minor semi-axis of an object in the sky and its error in arc seconds (the parameters B_IMAGE, ERRB_IMAGE);

pa—the position angle of an object measured from the north to east (the parameter THETA_J2000);

ell—the ellipticity of the object ${{1 - b} \mathord{\left/ {\vphantom {{1 - b} a}} \right. \kern-0em} a}$ (the parameter ELLIPTICITY);

radkron—the Kron pseudo-radius (the parameter KRON_RADIUS);

fluxauto, e_fluxauto— the flux after the background subtraction and its error inside the Kron ellipse (the parameters FLUX_AUTO, FLUXERR_AUTO);

magauto, e_magauto—the magnitude and its error inside the Kron ellipse (the parameters MAG_AUTO, MAGERR_AUTO);

radpetro—the Petrosian pseudo-radius (the parameter PETRO_RADIUS

fluxpetro, e_fluxpetro—the flux after the background subtraction and its error inside the the Petrosian ellipse (the parameters FLUX_PETRO, FLUXERR_PETRO);

magpetro, e_magpetro—the magnitude and its error inside the Petrosian ellipse (the parameters MAG_PETRO, MAGERR_PETRO);

badpixfraction—the fraction of “bad” pixels inside the Petrosian ellipse describing a galaxy;

quality—the photometry quality obtained on the basis of statistics of deviations of the ellipse parameters from the median values;

fits—the indicator of the file name in the local archive.

1.12 ps1candidate_crossid

The table of cross-identification of candidates with galaxies from the HyperLeda²⁰ database (Makarov et al. 2014):

projcell, subcell, candidate—the unique identifier of the object associated with the ps1candidate Table;

ra, dec—the right ascension and declination of the candidate in degrees for the epoch J2000.0;

pgc—the PGC galaxy number from HyperLeda database (Makarov et al. 2014);

flag—the code of the identification type;

userid—the user who performed the identification;

ctime—the time of entering the identification into the database.

1.13 ps1candidate_notes

Various notes made during the work with candidates:

projcell, subcell, candidate—the unique identifier of an object associated with the ps1candidate Table;

userid—the user who made a note;

ctime—the time of making a note;

note— the note itself.

1.14 STRUCTURE OF TABLES USED IN THE CLASSIFICATION SYSTEM

1.15 user

id—the unique login of a user;

name—the full username.

1.16 quiz

id—the unique identifier of the questionnaire;

title—the short description;

tbl—the name of the table with objects to classify;

retired—the maximum number of classifications of an object by different users.

1.17 quiz_question

id—the unique number of a question;

quizid—the indicator of the questionnaire in the quiz Table;

value—the assigned value of a characteristic;

description—the short description of a question;

bunch—the number of the question group;

input—determines the way of classification: radio—selection of one value from the set or checkbox—the presence or absence of this characteristic.