Star formation properties of spiral galaxies

The gas properties of barred and unbarredspiral galaxies are compared in two complete samples.It is found that two types of spiral galaxies do notdiffer to each other in atomic and molecular gascontents. On average there is 6 times more HI thanH₂ in spiral galaxies and the ratio MHI/MH2decreases from early to late types. The barred andunbarred spirals in general show a similar behaviorsof the gas-to-luminosity relationships, but also thereare certain differences between them such ascorrelation of two gas phases (HI and H₂) forunbarred galaxies. It is suggested that differentbehaviors of two types galaxies are due to the higherstar forming activity of barred with respect unbarredspirals. The expected values of HI and H₂ gascontents have been estimated using blue and far-infrared emission.     

Investigation of Barred Galaxies. VII. Comparative Statistics of SB and SA Galaxies. Near and Mid-IR Regions

The near and mid-IR properties of barred and unbarred spiral galaxies are discussed on the basis of complete samples that were compiled earlier. The two types of spirals are shown not to differ from one another in emission power in the near and mid-IR ranges. Multiple regression and principal component analysis have been applied to investigate near and mid-IR properties of SB and SA galaxies, particularly their relation to X-ray and radio continuum emissions. There are definite differences between SB and SA spirals in the near and mid-IR. In the case of SB galaxies, the compactness of 10 m emission is closely related to the J - H color index, and the redder J - H color corresponds to relatively more extended emission at 10 m. It is assumed that these are caused by the bar itself, which stimulates enhanced star formation in a barred galaxy with respect to unbarred spiral.     

The Effect of Bar on Star-forming Activities in Nuclear Regions of Nearby Spiral Galaxies

By using the SDSS spectra, we have studied the star formation properties of the nearby spiral galaxies selected from the Revised Bright Galaxy Sample, and tried to find the effect of bar structure on the star formation activity in the nuclear regions of nearby galaxies. The stellar population composition and the intensity of star formation activities of each sample galaxy are acquired by using the stellar population synthesis code—STARLIGHT, and the star formation properties of nuclear regions are compared with those of integral sample galaxies. We find that the star formation in barred spiral galaxies is more active than that of unbarred spirals, and that barred spirals have younger stellar populations.     

Barred galaxies. IV. Comparative statistics on SB and SA galaxies in the radio and x-ray ranges

The radio and xray properties of spiral galaxies with and without a bar are discussed on the basis of complete samples that we have compiled. The two types of spirals are shown not to differ from one another in emission power in the two indicated ranges. In the case of SB galaxies, the luminosities in the IR, radio, and xray ranges are closely related. The spectral indices of SB and SA galaxies in the 1.4–5 GHz range are the same, on the average. In the case of barred galaxies, however, a definite dependence is observed between the spectral index and both the IR and × ray luminosities, i.e., the spectral index increases as both luminosities increase. It is assumed that this is caused by the bar itself, which stimulates star formation in a barred galaxy. Translated from Astrofizika, Vol. 41. No. 4, pp. 599–608, October–December, 1998.     

Gas content of infrared luminous markarian galaxies

The atomic and molecular hydrogen gas properties of a complete sample of Markarian galaxies with flux density at 60 µm higher than 1.95 Jy are presented. We present the improved far-infrared luminosity function of Markarian galaxies; and its comparison with other samples. We find that 40% of the bright IRAS galaxies of far-infrared luminosity higher than 10^10.5 L are Markarian galaxies. There is an absence of correlation between HI content of Markarian galaxies and current star formation activity, implying that star formation in these systems has complex structure and it is not a simple function of the HI content. On the contrary, the H₂ content of Markarian galaxies is well correlated with star formation activity. It is argued that tight correlation between HI and H₂ contents is a consequence of transformation of atomic hydrogen into molecular.Published in Astrofizika, Vol. 38, No. 4, pp. 636–644, October–December, 1995.     

A new formula describing the scaffold structure of spiral galaxies

We describe a new formula capable of quantitatively characterizing the Hubble sequence of spiral galaxies including grand design and barred spirals. Special shapes such as ring galaxies with inward and outward arms are also described by the analytic continuation of the same formula. The formula is   r (φ) = A /log [ B tan   (φ/2 N )]  . This function intrinsically generates a bar in a continuous, fixed relationship relative to an arm of arbitrary winding sweep. A is simply a scale parameter while B , together with N , determines the spiral pitch. Roughly, greater N results in tighter winding. Greater B results in greater arm sweep and smaller bar/bulge, while smaller B fits larger bar/bulge with a sharper bar/arm junction. Thus B controls the 'bar/bulge-to-arm' size, while N controls the tightness much like the Hubble scheme. The formula can be recast in a form dependent only on a unique point of turnover angle of pitch – essentially a one-parameter fit, aside from a scalefactor. The recast formula is remarkable and unique in that a single parameter can define a spiral shape with either constant or variable pitch capable of tightly fitting Hubble types from grand design spirals to late-type large barred galaxies. We compare the correlation of our pitch parameter to Hubble type with that of the traditional logarithmic spiral for 21 well-shaped galaxies. The pitch parameter of our formula produces a very tight correlation with ideal Hubble type suggesting it is a good discriminator compared to logarithmic pitch, which shows poor correlation here similar to previous works. Representative examples of fitted galaxies are shown.     

Order and chaos in spiral galaxies

Spiral galaxies contain both ordered and chaotic orbits. In normal spirals the perturbations are weak (of order 2–10%) and most orbits are ordered. The density wave theory refers mainly to linear perturbations. Nonlinear effects appear in the outer parts of the open spirals (S_b, S_c) and produce the termination of these spirals near the 4/1 resonance. On the other hand in barred spirals the perturbations are relatively strong (of order 100%). Then the outer spirals and the envelope of the bar are composed mainly of chaotic orbits, while the main body of the bar is composed of ordered orbits. The chaotic orbits of the spiral arms of strong barred galaxies are sticky, i.e. they do not escape from the galaxy for at least a Hubble time. The forms of these spirals are delineated by the unstable manifolds of the unstable periodic orbits L_1, L_2 near the ends of the bar and of other unstable periodic orbits inside and outside corotation.     

Barred galaxies. I. A catalog

A catalog of barred spiral galaxies of types SB and SAB with B_T ≤ 13.5 and δ > -10° has been compiled. Some parameters of these galaxies are given. Translated from Astrofizika, Vol. 4L No. 1, pp. 5–21 January-March. 1998.     

Morphological dependence in the spatial orientations of galaxies around the Local Supercluster

We study the spatial orientation of 5 169 galaxies that have radial velocity 3 000 to 5 000 km s⁻¹. The ‘position angle–inclination’ method is used to find the spin vector and the projections of spin vector of the galaxy rotation axes. The spatial isotropic distribution is assumed to examine the non-random effects. For this, we have performed chi-square, Fourier, and auto-correlation tests. We found a random alignment of spin vectors of total galaxies with respect to the equatorial coordinate system. The spin vector projections of total galaxies is found to be oriented tangentially with respect to the equatorial center. The spiral galaxies show a similar orientation as shown by the total sample. Five subsamples of barred spiral (late-type) galaxies show a preferred alignment. However, early-type barred spirals show a random orientation. A weak morphological dependence is noticed in the subsamples of late type barred spirals. A comparison with the previous works and the possible explanation of the results will be presented.     

Barred galaxies. II. Comparative statistics on SB and SA galaxies in visible light

Various characteristics of galaxies with and without a bar are compared in two complete samples compiled by the authors. It is found that the two types of spiral galaxies hardly differ from each other in a number of parameters and properties, such as nuclear activity and degree of concentration in groups. Star formation evidently occurs more efficiently in barred galaxies, however. Bars are encountered more often in intermediate and late subtypes of disk galaxies. Barred galaxies in groups are redder, on the average, than those outside of groups. Luminosity functions are constructed both for galaxies with and without bars. Translated from Astrofizika, Vol. 4L No. 2, pp. 185–196, April-June, 1998     

The relation of dwarf galaxies with bright barred galaxies in virgo cluster

On the basis of extensive observational material it is statistically demonstrated that dwarf galaxies appear more often around barred galaxies than around normal spiral galaxies. Moreover, the more barred spiral galaxies there are in a given region, the more dwarf galaxies are found there as well.Translated from Astrofizika, Vol. 38, No. 1, pp. 45–53, January–March, 1995.     

H I observations of flat galaxies

We present the HI observations of 94 flat spiral galaxies from RFGC (Revised Flat Galaxy Catalog) and 14 galaxies from 2MFGC (the 2MASS selected Flat Galaxy Catalog) performed with the 100-m radio telescope in Effelsberg (Germany). HI fluxes, heliocentric radial velocities, and HI line widths are given for 65 detected galaxies. We present a mosaic of HI profiles. We calculated some of the global parameters of the galaxies and analyzed the linear correlations between them. The ratios of the total (indicative) masses of the galaxies to their luminosities lie within the range 0.4–8.2 with a mean of 3.8 (M_⊙/L_⊙), and the mean mass fraction of neutral hydrogen is 13%. Upper limits are given for the radio fluxes from 43 undetected galaxies.     

The evolution of barred spiral galaxies in the Hubble Deep Fields North and South

The frequency of barred spiral galaxies as a function of redshift contains important information on the gravitational influence of stellar discs in their dark matter haloes and may also distinguish between contemporary theories for the origin of galactic bulges. In this paper we present a new quantitative method for determining the strength of barred spiral structure, and verify its robustness to redshift-dependent effects. By combining galaxy samples from the Hubble Deep Field North with newly available data from the Hubble Deep Field South, we are able to define a statistical sample of 46 low-inclination spiral systems with I _814 W<23.2 mag. Analysing the proportion of barred spiral galaxies seen as a function of redshift, we find a significant decline in the fraction of barred spirals with redshift. The redshift distribution of 22 barred and 24 non-barred spirals with suitable inclinations is inconsistent with their being drawn from the same distribution at the 99 per cent confidence level. The physical significance of this effect remains unclear, but several possibilities include dynamically hotter (or increasingly dark-matter-dominated) high-redshift discs, or an enhanced efficiency in bar destruction at high redshifts. By investigating the formation of the 'orthogonal' axis of Hubble's classification tuning fork, our result complements studies of evolution in the early–late sequence, and pushes to later epochs the redshift at which the Hubble classification sequence is observed to be in place.     

Surface color photometry of five barred spiral galaxies

Distributions of the surface brightness and the surface color of five barred spiral galaxies expressed in the form of digital maps are presented. This is the first step to determine the composition of the components of barred spiral galaxies — bar, spiral arm, inner ring and outer ring — and to obtain an accurate picture of the dynamical model of a barred spiral galaxy. We have found that (a) the bar is redder than the spiral arm and has a color similar to that of the disk and (b) the inner ring of theSB(r) type galaxy is bluer than the bar and rather resembles the spiral arm.     

A model of the formation of spiral galaxies

It has been verified that the analytical results derived in a previous article for elliptical galaxies may also be used to describe spiral galaxies. Exploration of the model for small values of the principal parameter yields surface mass density distributions as functions of radius which, while always displaying the exponential disk, describe both of the subcategories of spiral galaxies. Within the constraints of the model, the two main questions concerning spirals posed some years ago by Freeman appear to be successfully addressed.An intrinsic model mechanism has been identified that could account for the extended state of elliptical galaxies, as opposed to the flat disks of spirals. In general, the model correctly describes the relative sizes of the various types of galaxies.     

BHαBAR: big Hα kinematical sample of barred spiral galaxies – I. Fabry–Perot observations of 21 galaxies

We present the Hα gas kinematics of 21 representative barred spiral galaxies belonging to the BHαBAR sample. The galaxies were observed with FaNTOmM, a Fabry–Perot integral-field spectrometer, on three different telescopes. The three-dimensional data cubes were processed through a robust pipeline with the aim of providing the most homogeneous and accurate data set possible useful for further analysis. The data cubes were spatially binned to a constant signal-to-noise ratio, typically around 7. Maps of the monochromatic Hα emission line and of the velocity field were generated and the kinematical parameters were derived for the whole sample using tilted-ring models. The photometrical and kinematical parameters (position angle of the major axis, inclination, systemic velocity and kinematical centre) are in relative good agreement, except perhaps for the later-type spirals.     

On the direction of rotation of the spirals in galaxies

The detection of trailing arms in twenty spiral galaxies, completed by the 60s, allowed one to suggest the overwhelming prevalence of this sense of rotation. Pasha and Dambis (1982) have recently determined the direction of rotation in a further 54 galaxies and found two leading spirals, NGC 4490 and NGC 5395. The current sample of galaxies with an established sense of rotation contains 79 trailing and two leading systems. The two spirals found to be leading belong to M51 type galaxies.In this paper we present a more detailed investigation of the system NGC 4490/85 which confirms that the arms in NGC 4490 are leading. Statistics are invoked to estimate a probable percentageX _p and an upper limitX _up of galaxies with leading arms. It gives, for 79 trailing and two leading spirals, the valuesX _p 3.5% andX _up 8.2%.     

The clustering of barred galaxies in the local Universe

We study the clustering properties of barred galaxies using data from the Sloan Digital Sky Survey. We compute projected redshift-space two-point cross-correlation functions   w _p( r _p)  for a sample of nearly 1000 galaxies for which we have performed detailed structural decompositions using the methods described in Gadotti. The sample includes 286 barred galaxies. The clustering of barred and unbarred galaxies of similar stellar mass is indistinguishable over all the scales probed (∼20 kpc–30 Mpc). This result also holds even if the sample is restricted to bars with bluer   g − i   colours (and hence younger ages). Our result also does not change if we split our sample of barred galaxies according to bar-to-total luminosity ratio, bar boxyness, effective surface brightness, length or the shape of the surface density profile within the bar. There is a hint that red, elliptical bars are more strongly clustered than red and less elliptical bars, on scales  ≳1 Mpc  , although the statistical significance is not high. We conclude that there is no significant evidence that bars are a product of mergers or interactions. We tentatively interpret the stronger clustering of the more elliptical bars as evidence that they are located in older galaxies, which reside in more massive haloes.     

Luminosity function of the field galaxies

The Schmidt method for constructing the luminosity function of galaxies is generalized to include the dependence of the density of galaxies on distance in the near universe. The logarithmic luminosity function (LLF) of the field galaxies as a function of morphological type is constructed. It is found that the LLF for all the galaxies, as well as separately for elliptical and lenticular galaxies, can be represented as a Schechter function within a narrow range of absolute magnitudes. The LLF for spiral galaxies is a Schechter function over a rather wide range of absolute magnitudes, −21.0 ≤ M ≤ −14 . The parameter M_* varies little over the spiral galaxies. The parameter α in the Schechter function decreases on going from early to later spirals. On going from elliptical to lenticular galaxies, from early spiral galaxies and onward to later spiral galaxies, a decrease in the average luminosity of the galaxies is observed in the bright end, −23 ≤ M ≤ −17.8 . The completeness and average density of the samples are estimated for galaxies of different morphological types. The average number density of all the galaxies within the range −23 ≤ M ≤ −13 is 0.126 Mpc^-3.     

Unusual properties of bar-within-ring galaxies and the projection effect model for barred spiral galaxies

Five anomalous properties of bar-within-ring galaxies, which comprise the majority of barred spiral galaxies, are reported. These properties appear to be in conflict with conventional ideas about galactic morphology, but are in keeping with the projection effect model for barred spiral galaxies.