Unbarred Spirals Research Articles

Investigation of the effect of bars on the properties of spiral galaxies: a multivariate statistical study

Subjective classification of spiral galaxies is not sufficient for studying the effect of bars on their physical characteristics. In reality the problem is to comprehend the complex correlations in a multivariate parametric space. Multivariate tools are the best ones for understanding this complex correlation. In this work an objective classification of a large set (26,089) of spiral galaxies was compiled as a value added galaxy catalogue from sdss DR 15 virtual data archive. Initially for dimensionality reduction, Independent Component Analysis is performed to determine a set of Independent Components that are linear combinations of 48 observed features (namely ionized lines, Lick indices, photometric and morphological properties). Subsequently a K-means cluster analysis is carried out on the basis of the 14 best chosen Independent Components to obtain 12 distinct homogeneous groups of spiral galaxies. Amongst these, 3 groups are the oldest ones (1.6 Gyr − 5.9 Gyr), while 5 groups fall in the medium aged category (1.4 Gyr − 1.6 Gyr), 2 groups consist of only unbarred spirals, 1 group is the youngest one and the remaining one is an outlier. In many groups there are clear indication of recurrent bar formation phenomena which is consistent with few previous simulation works. In order to study the robustness of the clusters with respect to the method of clustering, a second method of clustering by Gaussian Mixture Modeling Method (GMMBC) is applied.

H i Spectroscopy of Reverberation-mapped Active Galactic Nuclei

Abstract We present H i 21 cm spectroscopy from the Robert C. Byrd Green Bank Telescope for the host galaxies of 31 nearby active galactic nuclei with direct M BH measurements from reverberation mapping. These are the first published H i detections for 12 galaxies, and the spectral quality is generally an improvement over archival data for the remainder of the sample. We present measurements of emission-line fluxes, velocity widths, and recessional velocities from which we derive H i mass, total gas mass, and redshifts. Combining M GAS with constraints on M STARS allows exploration of the baryonic content of these galaxies. We find a typical M GAS /M STARS fraction of 10%, with a few reaching ∼30%–50%. We also examine several relationships between M STARS , M GAS , M BH , baryonic mass, and morphological type. We find a weak preference for galaxies with larger M GAS to host more massive black holes. We also find gas-to-stellar fractions to weakly correlate with later types in unbarred spirals, with an approximately constant fraction for barred spirals. Consistent with previous studies, we find declining M GAS /M STARS with increasing M stars , with a slope suggesting the gas reservoirs have been replenished. Finally, we find a clear relationship for M BH –M BARY with a similar slope as M BH –M STARS reported by Bentz & Manne-Nicholas. The dwarf Seyfert NGC 4395 appears to follow this relationship as well, even though it has a significantly higher gas fraction and smaller M BH than the remainder of our sample.

Galaxy Zoo: unwinding the winding problem – observations of spiral bulge prominence and arm pitch angles suggest local spiral galaxies are winding

We use classifications provided by citizen scientists though Galaxy Zoo to investigate the correlation between bulge size and arm winding in spiral galaxies. Whilst the traditional spiral sequence is based on a combination of both measures, and is supposed to favour arm winding where disagreement exists, we demonstrate that, in modern usage, the spiral classifications Sa-Sd are predominantly based on bulge size, with no reference to spiral arms. Furthermore, in a volume limited sample of galaxies with both automated and visual measures of bulge prominence and spiral arm tightness, there is at best a weak correlation between the two. Galaxies with small bulges have a wide range of arm winding, while those with larger bulges favour tighter arms. This observation, interpreted as revealing a variable winding speed as a function of bulge size, may be providing evidence that the majority of spiral arms are not static density waves, but rather wind-up over time. This suggests the "winding problem" could be solved by the constant reforming of spiral arms, rather than needing a static density wave. We further observe that galaxies exhibiting strong bars tend have more loosely wound arms at a given bulge size than unbarred spirals. This observations suggests that the presence of a bar may slow the winding speed of spirals, and may also drive other processes (such as density waves) which generate spiral arms. It is remarkable that after over 170 years of observations of spiral arms in galaxies our understanding of them remains incomplete.

Effect of bars on the galaxy properties

Aims: With the aim of assessing the effects of bars on disc galaxy properties, we present an analysis of different characteristics of spiral galaxies with strong, weak and without bars. Method: We identified barred galaxies from the Sloan Digital Sky Survey. By visual inspection, we classified the face-on spiral galaxies brighter than g<16.5 mag into strong-bar, weak-bar and unbarred. In order to provide an appropiate quantification of the influence of bars on galaxy properties, we also constructed a suitable control sample of unbarred galaxies with similar redshift, magnitude, morphology, bulge sizes, and local density environment distributions to that of barred galaxies. Results: We found 522 strong-barred and 770 weak-barred galaxies, representing a 25.82% of the full sample of spiral galaxies, in good agreement with previous studies. We also found that strong-barred galaxies show less efficient star formation activity and older stellar populations compared to weak-barred and unbarred spirals from the control sample. In addition, there is a significant excess of strong barred galaxies with red colors. The color-color and color-magnitude diagrams show that unbarred and weak-barred galaxies are more extended towards the blue zone, while strong-barred objects are mostly grouped in the red region. Strong-barred galaxies present an important excess of high metallicity values, compared to the other types, showing similar 12+log(O/H) distributions. Regarding the mass-metallicity relation, we found that weak-barred and unbarred galaxies are fitted by similar curves, while strong-barred ones show a curve which falls abruptly, with more significance in the range of low stellar masses (log[Mstar/Msun] < 10.0). These results would indicate that prominent bars produced an accelerating effect on the gas processing, reflected in the significant changes in the physical properties of their host.

The VIRUS-P Exploration of Nearby Galaxies (VENGA): spatially resolved gas-phase metallicity distributions in barred and unbarred spirals

We present a study of the excitation conditions and metallicity of ionized gas (Z_gas) in eight nearby barred and unbarred spiral galaxies from the VIRUS-P Exploration of Nearby Galaxies (VENGA) survey, which provides high spatial sampling and resolution (median ~ 387 pc), large coverage from the bulge to outer disc, broad wavelength range (3600-6800 Ang.), and medium spectral resolution (~ 120 km s^-1 at 5000 Ang.). Our results are: (1) We present high resolution gas excitation maps to differentiate between regions with excitation typical of Seyfert, LINER, or recent star formation. We find LINER-type excitation at large distances (3-10 kpc) from the centre, and associate this excitation with diffuse ionized gas (DIG). (2) After excluding spaxels dominated by Seyfert, LINER, or DIG, we produce maps with the best spatial resolution and sampling to date of the ionization parameter q, star formation rate, and Z_gas using common strong line diagnostics. We find that isolated barred and unbarred spirals exhibit similarly shallow Z_gas profiles from the inner kpc out to large radii (7-10 kpc or 0.5-1.0 R_25). This implies that if profiles had steeper gradients at earlier epochs, then the present-day bar is not the primary driver flattening gradients over time. This result contradicts earlier claims, but agrees with recent IFU studies. (3) The Z_gas gradients in our z ~ 0 massive spirals are markedly shallower, by ~ 0.2 dex kpc^-1, than published gradients for lensed lower mass galaxies at z ~ 1.5-2.0. Cosmologically-motivated hydrodynamical simulations best match this inferred evolution, but the match is sensitive to adopted stellar feedback prescriptions.

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.

Probing Cool and Warm Infrared Galaxies Using Photometric and Structural Measures

We have analyzed a sample of nearby cool and warm infrared (IR) galaxies using photometric and structural parameters. The set of measures include far-infrared color [C = log(S60 μm/S100 μm)], total IR luminosity (LTIR), radio surface brightness, and radio, near-infrared, and optical sizes. In a given luminosity range cool and warm galaxies are considered as those sources that are found approximately 1 σ below and above the mean color in the far-infrared C-LTIR diagram. We find that galaxy radio surface brightness is well correlated with color whereas size is less well correlated with color. Our analysis indicates that IR galaxies that are dominated by cool dust are large, massive spirals that are not strongly interacting or merging and presumably the ones with the least active star formation. Dust in these cool objects is less centrally concentrated than in the more typical luminous and ultraluminous IR galaxies that are dominated by warm dust. Our study also shows that low-luminosity early-type unbarred and transitional spirals are responsible for the large scatter in the C-LTIR diagram. Among highly luminous galaxies, late-type unbarred spirals are predominately warm, and early-type unbarred and barred spirals are systematically cooler. We highlight the significance of the C-LTIR diagram in terms of local and high-redshift submillimeter galaxies.

Secular Evolution via Bar‐driven Gas Inflow: Results from BIMA SONG

We present an analysis of the molecular gas distributions in the 29 barred and 15 unbarred spirals in the BIMA CO (J = 1-0) Survey of Nearby Galaxies (SONG). For galaxies that are bright in CO, we confirm the conclusion by Sakamoto et al. that barred spirals have higher molecular gas concentrations in the central kiloparsec. The SONG sample also includes 27 galaxies below the CO brightness limit used by Sakamoto et al. Even in these less CO-bright galaxies we show that high central gas concentrations are more common in barred galaxies, consistent with radial inflow driven by the bar. However, there is a significant population of early-type (Sa-Sbc) barred spirals (6 of 19) that have no molecular gas detected in the nuclear region and have very little out to the bar corotation radius. This suggests that in barred galaxies with gas-deficient nuclear regions, the bar has already driven most of the gas within the bar corotation radius to the nuclear region, where it has been consumed by star formation. The median mass of nuclear molecular gas is over 4 times higher in early-type bars than in late-type (Sc-Sdm) bars. Since previous work has shown that the gas consumption rate is an order of magnitude higher in early-type bars, this implies that the early types have significantly higher bar-driven inflows. The lower accretion rates in late-type bars can probably be attributed to the known differences in bar structure between early and late types. Despite the evidence for bar-driven inflows in both early and late Hubble-type spirals, the data indicate that it is highly unlikely for a late-type galaxy to evolve into an early type via bar-induced gas inflow. Nonetheless, secular evolutionary processes are undoubtedly present, and pseudobulges are inevitable; evidence for pseudobulges is likely to be clearest in early-type galaxies because of their high gas inflow rates and higher star formation activity.

Photometric properties and origin of bulges in SB0 galaxies

We have derived the photometric parameters for the structural components of a sample of fourteen SB0 galaxies by applying a parametric photometric decomposition to their observed I-band surface brightness distribution. We find that SB0 bulges are similar to bulges of the early-type unbarred spirals, i.e. they have nearly exponential surface brightness profiles () and their effective radii are strongly coupled to the scale lengths of their surrounding discs (). The photometric analysis alone does not allow us to differentiate SB0 bulges from unbarred S0 ones. However, three sample bulges have disc properties typical of pseudobulges. The bulges of NGC 1308 and NGC 4340 rotate faster than bulges of unbarred galaxies and models of isotropic oblate spheroids with equal ellipticity. The bulge of IC 874 has a velocity dispersion lower than expected from the Faber-Jackson correlation and the fundamental plane of the elliptical galaxies and S0 bulges. The remaining sample bulges are classical bulges, and are kinematically similar to lower-luminosity ellipticals. In particular, they follow the Faber-Jackson correlation, lie on the fundamental plane and those for which stellar kinematics are available rotate as fast as the bulges of unbarred galaxies.

Explorations in Hubble Space: A Quantitative Tuning Fork

In order to establish an objective framework for studying galaxy morphology, we have developed a quantitative two-parameter description of galactic structure that maps closely onto Hubble's original tuning fork. Any galaxy can be placed in this "Hubble space," where the x-coordinate measures position along the early-to-late sequence while the y-coordinate measures in a quantitative way the degree to which the galaxy is barred. The parameters defining Hubble space are sufficiently robust to allow the formation of Hubble's tuning fork to be mapped out to high redshifts. In the present paper, we describe a preliminary investigation of the distribution of local galaxies in Hubble space based on the CCD imaging atlas published by Frei et al. in 1996. We find that barred, weakly barred, and unbarred galaxies are remarkably well separated on this diagnostic diagram. The spiral sequence is clearly bimodal and indeed approximates a tuning fork: strongly barred and unbarred spirals do not simply constitute the extrema of a smooth unimodal distribution of bar strength but, rather, populate two parallel sequences. Strongly barred galaxies lie on a remarkably tight sequence, strongly suggesting the presence of an underlying unifying physical process. Rather surprisingly, weakly barred systems do not seem to correspond to objects bridging the parameter space between unbarred and strongly barred galaxies but, instead, form an extension of the regular spiral sequence. This relation lends support to models in which the bulges of late-type spirals originate from secular processes driven by bars.

Investigation of barred galaxies. vi. a comparative statistics of sb and sa galaxies. the cold gas properties

The gas properties of barred and unbarred spiral galaxies are compared in two complete samples. It is found that two types of spiral galaxies do not differ from each other in atomic and molecular gas contents. On average there is 6 times more HI than H2 in spiral galaxies and the ratio MH2/MHI decreases from early to late types. The barred and unbarred spirals in general show a similar behaviors of the gas-to-luminosity relationships, but also there are certain differences between them such as correlation of two gas phases (HI and H2)for unbarred galaxies. It is suggested that different behaviors of two types galaxies are due to the higher star forming activity of barred with respect unbarred spirals. The expected values of HI and H2 gas contents have been estimated using blue and far-infrared emission.

3.22. Star formation properties of barred galaxies

The main results of this study can be summarized in the following: (a)Magnitude-limited complete sample of barred galaxies was constructed. Space density of barred and unbarred galaxies at low luminosity range (M &gt;-20) almost the same. At the high (M&lt;-20) luminosity range about 30% of the galaxies are barred ones.(b)Bars do not have obvious influence on active nuclei. Presence or absence of bars does not related with the large scale galaxy environment.(c)Barred spirals, on average, have significantly higher relative star formation rate than that do unbarred galaxies.(d)Barred spirals exhibit tight correlations between FIR, radio and X-ray luminosities, while for unbarred spirals these luminosities do not correlated, which indicates on enhanced star formation activity in barred galaxies.(f)Group and non-group barred galaxies may differ by star formation activity.

Interstellar Abundance Gradients In NGC 2403: Comparison To M33

We present new long-slit spectra of 12 H II regions in the Scd spiral galaxy NGC 2403. Gas-phase element abundances for O, N, S, Ne, and Ar were estimated using direct measurements of electron temperature based on detections of [O III] λ4363, [S III] λ6312, and [O II] λ7320-7330, and from theoretical photoionization analysis. We find abundance gradients for O/H and N/O of -0.102 ± 0.009 dex kpc-1 and -0.032 ± 0.005 dex kpc-1, respectively. The relatively flat N/O gradient suggest a significant source of primary nitrogen. An upper limit for the C/O ratio for one H II region was determined from a Hubble Space Telescope FOS spectrum. A mild outward increasing gradient in S/O is seen at marginal significance (0.03 ± 0.02 dex kpc-1). We compare the abundance gradient and effective oxygen yield deduced for NGC 2403 with those determined for M33, another Scd galaxy with very similar structural parameters. We find close agreement in most of the chemical properties between NGC 2403 and M33. However, the effective yield for oxygen determined from closed box chemical evolution calculations is higher in M33 than in NGC 2403. The higher yield derived for M33 is similar to the case of H I-deficient Virgo spiral galaxies. We also compare NGC 2403 and M33 with a larger sample of unbarred spirals having abundance measurements. The global metallicity of the spirals correlates well with galaxy luminosity, as already noted from earlier investigations. The O/H gradient per unit disk scale length does not correlate with galaxy luminosity with possibly small intrinsic scatter, suggesting that spiral galaxies are homologous with regard to chemical evolution. The correlation between gas abundances and local surface brightness (mass density) in late-type spirals appears to be described well by chemical evolution models incorporating self-regulating star formation. However, the characteristic abundance at a given value of surface brightness correlates with galaxy luminosity. This suggests that an additional parameter which scales with galaxy mass influences the chemical properties of disks.

The Effect of Bars on the Fueling of Star Formation and Nonstellar Activity in Galaxy Nuclei

AbstractTheoretical studies suggest that large-scale stellar bars can be highly effective in delivering gas to the central few hundred parsecs of a spiral galaxy, which may then initiate rapid star formation. Further instabilities may lead to additional inflow to physical scales relevant for active galactic nuclei. We test these predictions in light of recent observations. Compared to unbarred spirals, barred galaxies of type S0-Sbc have a higher probability of exhibiting nuclear star formation, as well as a higher formation rate of massive stars; neither effect is present in spirals of later morphological type. Bars, on the other hand, do not have an obvious influence on active nuclei. We discuss the implications of these findings for the fueling of central star formation and active nuclei.

SELF-CONSISTENT MODELS OF BARRED SPIRAL GALAXIES

ABSTRACT Self-consistent models of barred spiral galaxies based on the observed properties of NGC3992, NGC1073, and NGC1398 are constructed and analyzed. The method of model construction is a slight modification of the technique developed by Contopoulos and Grosbol for the case of unbarred spirals. The main factors which influence self-consistency are the amplitude, pitch angle, scale length and z-thickness of the spirals, the mass of the bar, the angular velocity of the bar/spiral pattern, the central surface density and scale length of the disk, and the central value and slope of the velocity dispersion. Stochastic orbits whose Jacobi constants lie between the values at the Lagrange points L1 and L4 are found to play a significant role in supporting self-consistent spiral structure, especially in the regions just beyond the ends of the bar. Stochastic orbits whose Jacobi constants lie below this interval tend to fill more or less uniformly either rings in the outer disk or ovals in the bar region, depending on the regions to which they are confined. Stochastic orbits whose Jacobi constants lie above that of L4 also tend not to support any imposed structure. The model bars are predominantly comprised of elongated orbits trapped around the x1 family and terminate close to corotation. The response of gas to the forces of the most successful models is calculated using a two-dimensional smoothed particle hydrodynamics code. The results confirm that a bar alone is not sufficient to drive a strong spiral response in the gas of the outer disk. An underlying spiral structure in the more massive stellar component appears to be required. If stellar spirals are present, strong gas spirals may persist for long times.

Far-infrared luminosity functions of normal galaxies

A volume-limited sample (&lt;1400 km s^-1^ corrected for local motion) is constructed from the Zwicky catalog and IRAS data base to examine the far-infrared (FIR) luminosity functions of normal galaxies, and to investigate possible relationships between FIR emission and galaxy morphology. Quantitative and unbiased treatment is provided by "survival analysis" statistical methods. We find that the FIR distributions of normal galaxies are better fit by lognormal than Schechter functions. The total FIR emissivity (8 to 115 microns) of normal galaxies is approximately equal to half their emission in the B plus V optical bands. Normal galaxy FIR emission is uncorrelated with the basic S0-Sm Hubble sequence of spiral galaxy morphology, but appears to be affected by de Vaucouleurs' revised morphological classifications based on inner rings and S-shaped arms. Spirals with bars and inner rings are systematically fainter than unbarred spirals. We suggest that bars and rings reduce the amount or spatially confine the dust in spiral disks, resulting in lower efficiency conversion of optical and UV photons into the infrared.

Nuclear Starbursts in Barred Spirals

The first analysis of the Infrared Astronomical Satellite (IRAS) data revealed differences between barred and unbarred spirals. The study of Shapley-Ames galaxies, by De Jong et al (1984), revealed that barred spirals tend, on average, to be associated with “warmer” far infrared color temperatures and higher Lfir/Lblue ratios than unbarred spirals. In a related study Hawarden et al (1986) noted that barred and unbarred spirals could be partially segregated on the basis of the IRAS S25μm/S25μm flux ratio. Both sets of investigators attributed the differences, between barred and unbarred spirals, to a nuclear starburst in the barred types.

Inner ring structures in galaxies as distance indicators. I - Dimensionless systematics of inner rings

view Abstract Citations (53) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Inner ring structures in galaxies as distance indicators. I - Dimensionless systematics of inner rings de Vaucouleurs, G. ; Buta, R. Abstract The statistical properties of the inner ring and broken ring structures observed in lenticular and spiral galaxies are investigated in relation to galaxy classification, structure and absolute magnitude as a basis for the use of the rings as distance indicators. Analyses of the relative frequencies of ring structures in galaxies of different morphological families and stages along the revised Hubble sequence are presented which demonstrate the importance of selection effects due to apparent diameter and inclination, and it is shown that for a sample of over 500 RC2 spirals with large diameters and favorable inclinations, pure inner rings are not common among the barred spirals and least common among the unbarred spirals. Comparison of the axial ratios of the ring and parent galaxy indicates that the rings are flat structures in the galactic plane, and may be intrinsically elongated in barred spiral galaxies. Finally, statistical analyses of the ratios of the isophotal and metric galaxy diameters to the ring diameters reveal the ratios to depend strongly on spiral galaxy type and family, and weakly on variety and luminosity class. Publication: The Astrophysical Journal Supplement Series Pub Date: December 1980 DOI: 10.1086/190700 Bibcode: 1980ApJS...44..451D Keywords: Distance; Galactic Structure; Ring Structures; Diameters; Lenticular Bodies; Spiral Galaxies; Astrophysics full text sources ADS | data products NED (21) Related Materials (4) Part 2: 1982ApJS...48..219B Part 3: 1983ApJS...51..149B Part 4: 1983ApJ...266....1B Part 5: 1983ApJ...272..380B