Ultra-flat galaxies selected from RFGC catalog. III. Star formation rate

Abstract

We examine the star formation properties of galaxies with very thin disks selected from the Revised Flat Galaxy Catalog (RFGC). The sample contains 333 ultra-flat galaxies (UFG) at high Galactic latitudes, |b| > 10 • , with a blue major angular diameter of a ≥ 1. ′ 2, blue and red apparent axial ratios of (a/b) b > 10, (a/b) r > 8.5 and radial velocities within 10 000 km s −1. As a control sample for them we use a population of 722 more thick RFGC galaxies with (a/b) b > 7, situated in the same volume. The UFG distribution over the sky indicates them as a population of quite isolated galaxies. We found that the specific star formation rate, sSF R FUV , determined via the FUV GALEX flux, increases steadily from the early type to late type disks for both the UFG and RFGC-UFG samples, showing no significant mutual difference within each morphological type T. The population of UFG disks has the average H I-mass-to-stellar-mass ratio by (0.25 ± 0.03) dex higher than that of RFGC-UFG galaxies. Being compared with arbitrary orientated disks of the same type, the ultra-flat edge-on galaxies reveal that their total H I mass is hidden by self-absorption on the average by approximately 0.20 dex. We demonstrate that using the robust stellar mass estimate via B − K-color and galaxy type T for the thin disks, together with a nowaday accounting for internal extinction, yields their sSF R quantities definitely lying below the limit of −9.4 dex (yr −1). The collected observational data on UFG disks imply that their average star formation rate in the past has been approximately three times the current SF R. The UFG galaxies have also sufficient amount of gas to support their observed SF R over the following nearly 9 Gyrs.

Star Formation in thin Disks of Spiral Galaxies Seen Face-On

“…The star formation rate and the relative hydrogen content in the disks of Sc, Scd, and Sd galaxies seen edge-on [5,19] is in good agreement with the parameters obtained in this paper for spiral galaxies without bulges seen face-on. This agreement, in particular, implies that thin disks of Sc-Sd galaxies are essentially transparent in the 21 cm line for arbitrary angles of inclination of the disk to the line of sight.…”

“…The columns of Table 1 contain: (1) the name of the galaxy; (2) the morphological type according to the Vaucouleurs scale which we determined from multicolor images in the PanSTARRS survey [9]; (3) the apparent total magnitude magnitude of the galaxy in the B-band from the HyperLEDA data base [10]; (4) the Galactic extinction [11]; (5) the magnitude of the galaxy in the FUV-band; (6) the visible magnitude in the 21 cm neutral hydrogen line [10]; (7) the integrated K-band magnitude of the galaxy calculated from the B-magnitude and the morphological type (this relationship was obtained by approximating the data shown in Fig. 19 of [12]); (8) the distance to the galaxy (in Mpc) determined from the radial velocity V LG for a Hubble parameter H 0 = 73 km/s/Mpc; for nearby galaxies with V LG < 2500 km/s the distance is estimated using the model of [13], which accounts for a galaxy infall towards the…”

“…The behavior of the sSFR as a function of morphological type or of stellar mass in galaxies without visible signs of a bulge is still unclear. Melnyk et al [5] have examined a sample of ~500 ultra-flat (UF) spiral edgeon galaxies [6] for which the contribution of a bulge to the overall brightness of the galaxy is negligible. They concluded that on going from Sc to Sd types the specific rate of star formation increases by a factor of two.…”

Early-Type (E, S0) Galaxies in the Catalog of Isolated Galaxies (KIG)

“…Of these 11/12 (92%) are listed in our Table 1 3. Some basic properties (means and standard errors of mean) for ETG galaxies in the KIG The columns of Table 3 give: (1)-status the galaxies; (2)-number of galaxies corresponding to columns (3)-( 5); (3)-absolute -band magnitudes corrected for extinction according to Melnyk et al (2017); (4)-logarithmic stellar masses (in the units of the solar mass); ( 5)-absolute -band magnitudes adopted from HyperLEDA database corrected for extinction; (6)-the number of galaxies corresponding to columns ( 7) and ( 8);( 7)-logarithmic star-formation rates (in the units of yr ); ( 8)-logarithmic specific star-formation rates (in the units of yr ); ( 9)-the number of galaxies corresponding to column (10); ( 10)-logarithmic H I masses (in the units of the solar mass); ( 11)-the number of galaxies corresponding to columns ( 12) and ( 13); ( 12), ( 13)-galaxy colors from the SDSS survey.…”

‘Scraggy’ dark haloes around bulge-less spiral

“…The total B-magnitude is corrected for Galactic extinction; the inner extinction for face-on galaxies we prove to be zero. The K-band magnitude is calculated via the corrected B-magnitude and morphological type (Melnyk et al 2017). Calculating the satellite projected separation Rp, we use the galaxy distance D = VLG/H0 with the Hubble parameter H0 = 73 km/s/Mpc.…”