J/MNRAS/493/390 Study of spiral structure in galaxies (Savchenko+, 2020) ================================================================================ A multiwavelength study of spiral structure in galaxies. I. General characteristics in the optical. Savchenko S., Marchuk A., Mosenkov A., Grishunin K. =2020MNRAS.493..390S (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Galaxies, photometry ; Galaxy catalogs ; Optical Keywords: methods: data analysis - galaxies: spiral - galaxies: structure Abstract: Different spiral generation mechanisms are expected to produce different morphological and kinematic features. In this first paper in a series, we carefully study the parameters of spiral structure in 155 face-on spiral galaxies, selected from the Sloan Digital Sky Survey, in the three gri bands. We use a method for deriving a set of parameters of spiral structure, such as the width of the spiral arms, their fraction to the total galaxy luminosity, and their colour, which have not been properly studied before. Our method is based on an analysis of a set of photometric cuts perpendicular to the direction of a spiral arm. Based on the results of our study, we compare the main three classes of spirals: grand design, multi-armed, and flocculent. We conclude that: (i) for the vast majority of galaxies (86 per cent), we observe an increase of their arm width with Galactocentric distance; (ii) more luminous spirals in grand design galaxies exhibit smaller variations of the pitch angle with radius than those in less luminous grand design spirals; (iii) grand design galaxies show less difference between the pitch angles of individual arms than multi-armed galaxies. Apart from these distinctive features, all three spiral classes do not differ significantly by their pitch angle, arm width, width asymmetry, and environment. Wavelength dependence is found only for the arm fraction. Therefore, observationally we find no strong difference (except for the view and number of arms) between grand design, multi-armed, and flocculent spirals in the sample galaxies. Description: In this paper, we used SDSS gri-band images to perform a detailed analysis of the spiral structure in the 155 face-on non-interacting spiral galaxies. Our sample is mostly composed of multi-armed and grand design galaxies, with a fraction of flocculent galaxies, in which at least one arm could be visually traced. In our study, we used an approach of fitting an arm profile by creating a series of photometric cuts perpendicular to its direction. For tracing the spiral structure, we start from the inner galaxy region to the outermost regions to which we are able to trace the spirals. Along with the pitch angle and its variation with radius, we measured, for the first time based on the spiral view in the optical, the arm width and its variation with Galactocentric distance, the fraction of the spiral structure to the total galaxy luminosity, and its colour. Coupling with the arm number and the general arm class (grand design, flocculent, or multi-armed), these quantities define the photometric properties of the spiral structure in galaxies, which can in principle be used to distinguish between different mechanisms of generating spiral structure in galaxies. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 67 155 General characteristics of the sample galaxies table2.dat 55 155 Results of the fitting for the r band -------------------------------------------------------------------------------- See also: V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Name Galaxy name (PCGNNNNNNN) 12- 16 F5.1 Mpc Dist Distance calculated from the best distance modulus from HyperLeda 18- 22 F5.3 kpc/arcsec Scale Scale calculated from the best distance modulus from HyperLeda 24- 27 F4.2 arcmin r25 Semimajor axis of the isophote 25mag/arcsec^2^ in the r band 29- 32 F4.2 --- q25 Median flattening between the 24-25mag/arcsec^2^ isophotes in the r band 34- 38 F5.2 mag rmag Apparent asymptotic magnitude in the r-band (1) 40- 45 F6.2 mag rMAG Absolute magnitude in the r-band (1) 47- 50 F4.2 mag g-r g-r colour index (2) 52- 56 F5.2 mag r-i r-i colour index (2) 58- 61 F4.1 --- Type Numerical morphological type from HyperLeda 63- 65 A3 --- Env Environment (3) 67 A1 --- Bar [+ ] Bar presence according to the visual inspection -------------------------------------------------------------------------------- Note (1): Apparent asymptotic and absolute magnitudes in the r band calculated from the growth curve, corrected for the Milky Way extinction (Schlafly & Finkbeiner 2011ApJ...737..103S) Note (2): Colours calculated from the corresponding asymptotic magnitudes and corrected for the Milky Way extinction (Schlafly & Finkbeiner 2011ApJ...737..103S) Note (3): Environment as follows: G = belongs to a group (information from NED) g = belongs to a group (information from Tempel et al. 2012A&A...540A.106T, Cat. J/A+A/540/A106) P = belongs to a pair (information from NED) p = belongs to a pair (information from Tempel et al. 2012A&A...540A.106T, Cat. J/A+A/540/A106) T = belongs to a triple (information from NED) t = belongs to a triple (information from Tempel et al. 2012A&A...540A.106T, Cat. J/A+A/540/A106) I = isolated galaxy (information from NED) i = isolated galaxy (information from Tempel et al. 2012A&A...540A.106T, Cat. J/A+A/540/A106) C = belongs to a cluster (information from NED) C = belongs to a cluster (information from Tempel et al. 2012A&A...540A.106T, Cat. J/A+A/540/A106) ? = means that classification is found neither in NED nor in Tempel et al. (2012A&A...540A.106T, Cat. J/A+A/540/A106) and we classified the galaxy environment on our own using the SDSS SkyServer Navigate tool on the basis of visual closeness to the target galaxy and known spectroscopic redshift -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Name Galaxy name (PCGNNNNNNN) 12- 15 F4.1 deg Mean pitch angle averaged for all spiral arms we traced (1) 17- 19 F3.1 --- Psirel ? Relative pitch angle variation along the radius 21- 24 F4.2 --- w ? Mean width of spiral arms (in units of r_25_) averaged for all spiral arms we traced 26- 32 F7.4 --- a ? Slope of the best linear fit to the radial width variation (2) 34- 38 F5.2 --- Asym ? Mean asymmetry of the cuts (3) 40- 43 F4.2 --- farms ? Fraction of the spiral pattern in the total galaxy flux in the r band 45- 48 F4.2 mag g-r g-r colour of the spiral pattern 50 A1 --- Typearms [GMF] Arm class (4) 52- 53 A2 --- l_Narms [>= ] Limit flag on Narms 55 I1 --- Narms Number of arms -------------------------------------------------------------------------------- Note (1): The pitch angle {Psi} is defined as the angle between the tangent of the spiral and azimuthal directions Note (2): Positive values mean that the width increases with radius Note (3): Positive values mean that the inner slope of the cuts is steeper Note (4): Arm class as follows: G = Grand design (34/155) M = Multi-armed (101/155) F = Flocculent (20/155) -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Ana Fiallos [CDS] 30-Mar-2023