S0 Galaxies Research Articles

Star formation in outer rings of S0 galaxies

Aims.Although S0 galaxies are usually thought to be “red and dead”, they often demonstrate star formation that is organized in ring structures. We try to clarify the nature of this phenomenon and its difference from star formation in spiral galaxies. Two early-type galaxies with outer rings, NGC 6534 and MCG 11-22-015, were selected to be studied.Methods.After inspecting the gas excitation in the rings using the Baldwin–Phillips–Terlevich method, we estimated the star formation rates (SFR) in the two outer rings of our galaxies using several SFR indicators derived from narrow-band photometry in the Hαemission line and archival GALEX ultraviolet images of the galaxies.Results.The ionized gas is excited by young stars in the ring of NGC 6534 and partly by shocks in MCG 11-22-015. The oxygen abundances in the HII regions of the rings are close to solar. The derived SFRs allow us to qualitatively restore star formation histories (SFH) in the rings: in NGC 6534, the SFH has been flat during the last 100–200 Myr, and in MCG 11-22-015, the star formation has started only a few Myr ago. We suggest that the rings in NGC 6534 and MCG 11-22-015 have different natures: the former is a resonant ring supplied with gas perhaps through tidal effects, and the latter has been produced by a satellite accretion. Recent outer gas accretion is implied in both cases.

SDSS-IV MaNGA PyMorph Photometric and Deep Learning Morphological Catalogues and implications for bulge properties and stellar angular momentum

We describe the SDSS-IV MaNGA PyMorph Photometric (MPP-VAC) and MaNGA Deep Learning Morphology (MDLM-VAC) Value Added Catalogs. The MPP-VAC provides photometric parameters from S\'ersic and S\'ersic+Exponential fits to the 2D surface brightness profiles of the MaNGA DR15 galaxy sample. Compared to previous PyMorph analyses of SDSS imaging, our analysis of the MaNGA DR15 incorporates three improvements: the most recent SDSS images; modified criteria for determining bulge-to-disk decompositions; and the fits in MPP-VAC have been eye-balled, and re-fit if necessary, for additional reliability. A companion catalog, the MDLM-VAC, provides Deep Learning-based morphological classifications for the same galaxies. The MDLM-VAC includes a number of morphological properties (e.g., a TType, and a finer separation between elliptical and S0 galaxies). Combining the MPP- and MDLM-VACs allows to show that the MDLM morphological classifications are more reliable than previous work. It also shows that single-S\'ersic fits to late- and early-type galaxies are likely to return S\'ersic indices of $n \le 2$ and $\ge 4$, respectively, and this correlation between $n$ and morphology extends to the bulge component as well. While the former is well-known, the latter contradicts some recent work suggesting little correlation between $n$-bulge and morphology. Combining both VACs with MaNGA's spatially resolved spectroscopy allows us to study how the stellar angular momentum depends on morphological type. We find correlations between stellar kinematics, photometric properties, and morphological type even though the spectroscopic data played no role in the construction of the MPP- and MDLM-VACs.

Gradients of Metallicity and Age of Stars in the Dwarf Spheroidal Galaxies KKs 3 and ESO 269-66

We compare the properties of the stellar populations of the globular clusters and field stars in two dwarf spheroidal galaxies (dSphs): ESO 269-66, a near neighbor of the giant S0 galaxy NGC 5128, and KKs 3, one of the few extremely isolated dSphs within 10 Mpc. The histories of star formation in these galaxies are known from previous work on deep stellar photometry of images from the Hubble Space Telescope (HST). The age and metal content for the nuclear globular clusters in KKs 3 and ESO 269-66 are known from published spectroscopic studies: T = 12.6 billion years, Fe/H] = -1.5, and -1.55 dex. We use the Sersic function to construct and analyze the profiles of the surface density of the stars with high and low metallicities (red and blue) in KKs 3 and ESO 269-66, and show that (1) the profiles of the density of red stars are steeper than those of blue stars, which is indicative of gradients of metallicity and age in the galaxies, and (2) the globular clusters in KKs 3 and ESO 269-66 contain roughly 4 and 40%, respectively, of all the old stars in the galaxies with metallicities [Fe / H] ~ -1.5 ÷ -1.6 dex and ages of 12-14 billion years. The globular clusters are, therefore, relicts of the first, most powerful bursts of star formation in the central regions of these objects. It is probable that, because of its isolation, KKs 3 has lost a smaller fraction of old low-metallicity stars than ESO 269-66. Keywords: galaxies: dwarf- galaxies: star clusters- galaxies: KKs 3, ESO 269-66

A New Perspective on the Large-scale Tidal Effect on the Galaxy Luminosity and Morphology

Abstract We study the mean tidal coherence of galaxy environments as a function of intrinsic luminosity determined by the absolute r-band magnitude. The tidal coherence of a galaxy environment is estimated as the cosine of the angle between two minor eigenvectors of the tidal field smoothed at the scales of 2 and 30 h −1 Mpc, respectively, centered on each of the local galaxies from the Sloan Digital Sky Data Release 10. Creating four luminosity-selected samples of the Sloan galaxies, we control them to have identical density distributions in order to nullify the dominant effect of the local density. The samples containing more luminous wall and field galaxies were found to yield lower mean values of the tidal coherence, which is a trend that turns out to be robust against the variation of the smoothing scales. At a fixed morphology, the same trend is found for the late-type spiral and lenticular galaxies in both of the field and wall environments. The early-type spiral field galaxies show no significant dependence on the tidal coherence, while both of the least and most luminous elliptical wall galaxies are found to dwell in the regions with highest tidal coherence.

A catalogue of nuclear stellar velocity dispersions of nearby galaxies from Hα STIS spectra to constrain supermassive black hole masses

We present new measurements for the nuclear stellar velocity dispersion $\sigma_{\ast}$ within sub-arcsecond apertures for 28 nearby galaxies. Our data consist of Space Telescope Imaging Spectrograph (STIS) long-slit spectra obtained with the G750M grating centred on the H$\alpha$ spectral range. We fit the spectra using a library of single stellar population models and Gaussian emission lines, while constraining in most cases the stellar-population content from an initial fit to G430L STIS spectra. We illustrate how these $\sigma_{\ast}$ measurements can be useful for constraining the mass $M_{\bullet}$ of supermassive black holes (SBHs) by concentrating on the cases of the lenticular galaxies NGC4435 and NGC4459. These are characterized by similar ground-based half-light radii stellar velocity dispersion $\sigma_{\rm e}$ values but remarkably different $M_{\bullet}$ as obtained from modelling their central ionised-gas kinematics, where NGC4435 appears to host a significantly undermassive SBH compared to what is expected from the $M_{\bullet}-\sigma_{\rm e}$ relation. For both galaxies, we build Jeans axisymmetric dynamical models to match the ground-based stellar kinematics obtained with SAURON integral-field spectrograph, including a SBH with $M_{\bullet}$ value as predicted by the $M_{\bullet}-\sigma_{\rm e}$ relation and using high-resolution HST images taken with the Advanced Camera for Surveys to construct the stellar-mass model. By mimicking the HST observing conditions we use such reference models to make a prediction for the nuclear $\sigma_{\ast}$ value. Whereas this was found to agree with our nuclear $\sigma_{\ast}$ measurement for NGC4459, for NGC4435 the observed $\sigma_{\ast}$ is remarkably smaller than the predicted one, which further suggests that this galaxy could host an undermassive SBH.

SDSS-IV MaNGA: the formation sequence of S0 galaxies

Gas stripping of spiral galaxies or mergers are thought to be the formation mechanisms of lenticular galaxies. In order to determine the conditions in which each scenario dominates, we derive stellar populations of both the bulge and disk regions of 279 lenticular galaxies in the MaNGA survey. We find a clear bimodality in stellar age and metallicity within the population of S0s and this is strongly correlated with stellar mass. Old and metal-rich bulges and disks belong to massive galaxies, and young and metal-poor bulges and disks are hosted by low-mass galaxies. From this we conclude that the bulges and disks are co-evolving. When the bulge and disk stellar ages are compared, we find that the bulge is almost always older than the disk for massive galaxies ($\textrm{M}_{\star} > 10^{10}~\textrm{M}_{\odot}$). The opposite is true for lower mass galaxies. We conclude that we see two separate populations of lenticular galaxies. The old, massive, and metal-rich population possess bulges that are predominantly older than their disks, which we speculate may have been caused by morphological or inside-out quenching. In contrast, the less massive and more metal-poor population have bulges with more recent star formation than their disks. We postulate they may be undergoing bulge rejuvenation (or disk fading), or compaction. Environment doesn't play a distinct role in the properties of either population. Our findings give weight to the notion that while the faded spiral scenario likely formed low-mass S0s, other processes, such as mergers, may be responsible for high-mass S0s.

Formation of S0 galaxies through mergers

Context. Major mergers are popularly considered too destructive to produce the relaxed regular structures and the morphological inner components (ICs) usually observed in lenticular (S0) galaxies.Aims. We aim to test if major mergers can produce remnants with realistic S0 morphologies.Methods. We have selected a sample of relaxed discy remnants resulting from the dissipative merger simulations of the GalMer database and derived their properties mimicking the typical conditions of current observational data. We have compared their global morphologies, visual components, and merger relics in mock photometric images with their real counterparts.Results. Only Ȉ1–2 Gyr after the full merger, we find that: 1) many remnants (67 major and 29 minor events) present relaxed structures and typical S0 or E/S0 morphologies, for a wide variety of orbits and even in gas-poor cases. 2) Contrary to popular expectations, most of them do not exhibit any morphological traces of their past merger origin under typical observing conditions and at distances as nearby as 30 Mpc. 3) The merger relics are more persistent in minor mergers than in major ones for similar relaxing time periods. 4) No major-merger S0-like remnant develops a significant bar. 5) Nearly 58% of the major-merger S0 remnants host visually detectable ICs, such as embedded inner discs, rings, pseudo-rings, inner spirals, nuclear bars, and compact sources, very frequent in real S0s too. 6) All remnants contain a lens or oval, identically ubiquitous in local S0s. 7) These lenses and ovals do not come from bar dilution in major-merger cases, but are associated with stellar halos or embedded inner discs instead (thick or thin).Conclusions. The relaxed morphologies, lenses, ovals, and other ICs of real S0s do not necessarily come from internal secular evolution, gas infall, or environmental mechanisms, as traditionally assumed, but they can result from major mergers as well.

The Structure of Large-scale Stellar Disks in Cluster Lenticular Galaxies∗

Abstract By obtaining imaging data in two photometric bands for 60 lenticular galaxies—members of eight southern clusters—with the Las Cumbres Observatory one-meter telescope network, we have analyzed the structure of their large-scale stellar disks. The parameters of radial surface-brightness profiles have been determined (including also disk thickness), and all the galaxies have been classified into pure exponential (Type I) disk surface-brightness profiles, truncated (Type II) and antitruncated (Type III) piecewise exponential disk surface-brightness profiles. We confirm the previous results of some other authors that the proportion of surface-brightness profile types is very different in environments of different density: in the clusters, the Type-II profiles are almost absent while according to the literature data, in the field they constitute about one-quarter of all lenticular galaxies. The Type-III profiles are equally presented in the clusters and in the field, while following similar scaling relations; but by undertaking an additional structural analysis including the disk thickness determination we note that some Type-III disks may be a combination of a rather thick exponential pseudobulge and an outer Type-I disk. Marginally, we detect a shift of the scaling relation toward higher central surface brightnesses for the outer segments of Type-III disks and smaller thickness of the Type-I disks in the clusters. Both effects may be explained by enhanced radial stellar migration during disk galaxy infall into a cluster that in particular represents an additional channel for Type-I disk shaping in dense environments.

A SALT Spectral Study of S0s Hosting Pseudobulges

We present a SALT-RSS spectroscopic study of a sample of S0 galaxies established by Vaghmare et al. (2015) as having pseudobulges using a combination of photometric criteria. We extract the spectra of various regions along the galaxy major axis using standard long-slit spectroscopic reduction procedures and model the spectra using STARLIGHT to derive detailed star formation histories. The central spectra of galaxies without bars in our sample reveal a complex star formation history, which is consistent with the belief that pseudobulges have a history of star formation distributed over extended periods of time. The spectra of the unbarred galaxies contain strong emission lines such as H $\alpha$, indicating active star formation, which appears to be in contradiction with the expectation that S0 galaxies have been stripped of gas. In the case of the two barred galaxies in the sample, the spectrum is dominated by light from a much older stellar population. This seems to suggest an accelerated formation of the pseudobulge made possible by the action of the bar. One of these galaxies appears to have exhausted its reservoir of gas and thus has no signature of a recently formed population of stars while the other galaxy has managed to give rise to new stars through a recent funnelling action. We have also confirmed the influence of bars on the nature of the stellar population in a pseudobulge using an alternate sample based on the SDSS

X-ray cavities in the hot corona of the lenticular galaxy NGC 4477

NGC 4477 is a low-mass lenticular galaxy in the Virgo Cluster, residing at 100\,kpc to the north of M87. Using a total of 116\,ks {\sl Chandra} observations, we study the interplay between its hot ($\sim$0.3\,keV) gas halo and the central supermassive black hole. A possible cool core is indicated by the short cooling time of the gas at the galaxy centre. We identify a pair of symmetric cavities lying 1.1\,kpc southeast and 0.9\,kpc northwest of the galaxy centre with diameters of 1.3\,kpc and 0.9\,kpc, respectively. We estimate that these cavities are newly formed with an age of $\sim$4\,Myr. No radio emission is detected at the positions of the cavities with the existing VLA data. The total energy required to produce the two cavities is $\sim$$10^{54}$\,erg, at least two orders of magnitude smaller than that of typical X-ray cavities. NGC 4477 is arguably far the smallest system and the only lenticular galaxy in which AGN X-ray cavities have been found. It falls on the scaling relation between the cavity power and the AGN radio luminosity, calibrated for groups and clusters. Our findings suggest that AGN feedback is universal among all cool core systems. Finally, we note the presence of molecular gas in NGC~4477 in the shape of a regular disk with ordered rotation, which may not be related to the feedback loop.

Atlas of Hαimages for five hundred nearest dwarf galaxies

AbstractResults of mass imaging nearby dwarf galaxies in emission Hαline and red continuum with the 6-meter BTA telescope are available via the address:http://www.sao.ru/lv/lvgdb. The sample of dwarfs limited by a distance of 11 Mpc contains about 500 objects. Their Hα- fluxes are used to derive integrated and specific star formation rates of the galaxies. We evaluate the consistency between star formation rates obtained from our Hα-survey and GALEX far-ultraviolet survey. We fix a systematic rise of the ratio SFR(FUV)/SFR(Hα) with the decreasing stellar mass of dwarf galaxies. In the sample there were included only galaxies of late types: T = 10 (Ir), 9 (Im, BCD), 8 (Sdm), 7 (Sd), 6 (Scd), since elliptical and lenticular galaxies, and also spiral with massive bulges, have a significantly different history of star formation.

Evidence for the formation of the young counter-rotating stellar disk from gas acquired by IC 719

Aims. The formation scenario of extended counter-rotating stellar disks in galaxies is still debated. In this paper, we study the S0 galaxy IC 719 known to host two large-scale counter-rotating stellar disks in order to investigate their formation mechanism. Methods. We exploit the large field of view and wavelength coverage of the Multi Unit Spectroscopic Explorer (MUSE) spectrograph to derive two-dimensional (2D) maps of the various properties of the counter-rotating stellar disks, such as age, metallicity, kinematics, spatial distribution, the kinematical and chemical properties of the ionized gas, and the dust map. Results. Due to the large wavelength range, and in particular to the presence of the Calcium Triplet λλ8498, 8542, 8662 Å (CaT hereafter), the spectroscopic analysis allows us to separate the two stellar components in great detail. This permits precise measurement of both the velocity and velocity dispersion of the two components as well as their spatial distribution. We derived a 2D map of the age and metallicity of the two stellar components, as well as the star formation rate and gas-phase metallicity from the ionized gas emission maps. Conclusions. The main stellar disk of the galaxy is kinematically hotter, older, thicker and with larger scale-length than the secondary disk. There is no doubt that the latter is strongly linked to the ionized gas component: they have the same kinematics and similar vertical and radial spatial distribution. This result is in favor of a gas accretion scenario over a binary merger scenario to explain the origin of counter-rotation in IC 719. One source of gas that may have contributed to the accretion process is the cloud that surrounds IC 719.

The Carnegie-Irvine Galaxy Survey. VII. Constraints on the Origin of S0 Galaxies from Their Photometric Structure

Abstract Using high-quality optical images from the Carnegie-Irvine Galaxy Survey, we perform multicomponent decompositions of S0 galaxies (S0s) to derive accurate structural parameters to constrain their physical origin. Many S0s do not host prominent bulges. S0s have a broad distribution of bulge-to-total ratios (B/T) and Sérsic indices (n), with average values of B/T = 0.34 ± 0.15 and n = 2.62 ± 1.02, qualitatively consistent with the notion that S0s define a parallel sequence with and may have evolved from spiral galaxies. This is further reinforced by the incidence of bars and lenses in S0s, which, when compared with the statistics in spirals, supports the idea that lenses are demised bars. However, despite their wide range of prominence, the bulges of S0s form a surprisingly uniform sequence on both the Kormendy and fundamental plane relations. There is no evidence for population dichotomy or other indications of differentiation into classical and pseudo bulges. Most of the S0s reside in the field and in groups; cluster environment is not a necessary condition for S0 production. The properties of S0 bulges show little correlation with environmental indicators, after the dependence of galaxy stellar mass on environment is taken into account. As the bulges of late-type spirals and S0s are intrinsically different, and environmental effects that may account for such evolution appear to be minimal, we conclude that late-type spirals are not plausible progenitors of S0s. The bulges of S0s likely formed at an early epoch, after which secular processes contributed little to their subsequent evolution.

Forming Lenticular Galaxies via Violent Disk Instability

Abstract Lenticular galaxies are generally thought to have descended from spirals via morphological transformation, although recent numerical simulations have shown that minor or even major mergers can also lead to an S0-like remnant. These mechanisms, however, are active in a dense environment such as a group or a cluster of galaxies—making it harder to explain the remarkable fraction of S0s found in the field. Here, we propose a new mechanism to form such lenticular galaxies. We show that an isolated cold disk settled into rotational equilibrium becomes violently unstable—leading to fragmentation and formation of stellar clumps that, in turn, not only cause the bulge to grow, but also increase the stellar disk velocity dispersion optimally in less than a billion years. Subsequently, the galaxy evolves passively without any conspicuous spiral structure. The final galaxy models resemble remarkably well the morphology and stellar kinematics of the present-day S0s observed by the Planetary Nebulae spectrograph. Our findings suggest a natural link between the high-redshift clumpy progenitors and the present-day S0 galaxies.

A Universal Entropy Profile for the Hot Atmospheres of Galaxies and Clusters within R2500

Abstract We present atmospheric gas entropy profiles for 40 early-type galaxies and 110 clusters spanning several decades of halo mass, atmospheric gas mass, radio jet power, and galaxy type. We show that within ∼0.1R 2500 the entropy profiles of low-mass systems, including ellipticals, brightest cluster galaxies, and spiral galaxies, scale approximately as K ∝ R 2/3. Beyond ∼0.1R 2500 entropy profiles are slightly shallower than the K ∝ R 1.1 profile expected from gravitational collapse alone, indicating that heating by active galactic nuclei (AGN) feedback extends well beyond the central galaxy. We show that the K ∝ R 2/3 entropy profile shape indicates that thermally unstable cooling is balanced by heating where the inner cooling and free-fall timescales approach a constant ratio. Hot atmospheres of elliptical galaxies have a higher rate of heating per gas particle compared to those of central cluster galaxies. This excess heating may explain why some central cluster galaxies are forming stars while most early-type galaxies have experienced no significant star formation for billions of years. We show that the entropy profiles of six lenticular and spiral galaxies follow the R 2/3 form. The continuity between central galaxies in clusters, giant ellipticals, and spirals suggests perhaps that processes heating the atmospheres of elliptical and brightest cluster galaxies are also active in spiral galaxies.

Chromodynamical analysis of lenticular galaxies using globular clusters and planetary nebulae

Recovering the origins of lenticular galaxies can shed light on the understanding of galaxy formation and evolution, since they present properties that can be found in both elliptical and spiral galaxies. In this work we study the kinematics of the globular cluster (GC) systems of three lenticular galaxies located in low density environments (NGC 2768, NGC 3115 and NGC 7457), and compare them with the kinematics of planetary nebulae (PNe). The PNe and GC data come from the Planetary Nebulae Spectrograph and the SLUGGS Surveys. Through photometric spheroid-disc decomposition and PNe kinematics we find the probability for a given GC to belong to either the spheroid or the disc of its host galaxy or be rejected from the model. We find that there is no correlation between the components that the GCs are likely to belong to and their colours. Particularly, for NGC 2768 we find that its red GCs display rotation preferentially at inner radii (Re<1). In the case of the GC system of NGC 3115 we find a group of GCs with similar kinematics that are not likely to belong to either its spheroid nor disc. For NGC 7457 we find that 70% of its GCs are likely to belong to the disc. Overall, our results suggest that these galaxies assembled into S0s through different evolutionary paths. Mergers seem to have been very important for NGC 2768 and NGC 3115 while NGC 7457 is more likely to have experienced secular evolution.

On the observational diagnostics to separate classical and disk-like bulges

Flattened bulges with disk-like properties are considered to be the end product of secular evolution processes at work in the inner regions of galaxies. On the contrary, classical bulges are characterized by rounder shapes and thought to be similar to low-luminosity elliptical galaxies. We aim at testing the variety of observational diagnostics which are commonly adopted to separate classical from disk-like bulges in nearby galaxies. We select a sample of eight unbarred lenticular galaxies to be morphologically and kinematically undisturbed with no evidence of other components than bulge and disk. We analyze archival data of broad-band imaging from SDSS and integral-field spectroscopy from the ATLAS$^{\rm 3D}$ survey to derive the photometric and kinematic properties, line-strength indices, and intrinsic shape of the sample bulges. We argue that the bulge S\'ersic index is a poor diagnostics to discriminate different bulge types. We find that the combination of line-strength with either kinematic or photometric diagnostics does not provide a clear separation for half of the sample bulges. We include for the first time the intrinsic three-dimensional shape of bulges as a possible discriminant of their nature. All bulges turn out to be thick oblate spheroids, but only one has a flattening consistent with that expected for outer disks. We conclude that bulge classification may be difficult even adopting all observational diagnostics proposed so far and that classical and disk-like bulges could be more confidently identified by considering their intrinsic shape.

Evolution of the anti-truncated stellar profiles of S0 galaxies since z = 0.6 in the SHARDS survey

Context. Anti-truncated lenticular galaxies (Type-III S0s) present tight scaling relations between their surface brightness photometric and structural parameters. Although several evolutionary models have been proposed for the formation of these structures, the observations of Type-III S0 galaxies are usually limited to the local Universe. Aims. We aim to compare the properties of Type-III discs in a sample of S0 galaxies at 0.2 &lt; z &lt; 0.6 with those of the local Universe. In this paper, we study the evolution of the photometric and structural scaling relations measured in the rest-frame R-band with z and the possible differences between the rest-frame (B − R) colours of the inner and outer disc profiles. Methods. We make use of a sample of 14 Type-III E/S0–S0 galaxies at 0.2 &lt; z &lt; 0.6 from the GOODS-N field identified and characterised in a previous paper. We study whether or not the correlations found in local Type-III S0 galaxies were present ~6 Gyr ago. We analyse the distribution of the surface brightness characteristic parameters (Rbreak, μbreak, hi, ho, μ0,i and μ0,o) as a function of the stellar mass and look to see if there is a significant change with z. We also derive their rest-frame (B − R) colour profiles. Finally, we compare these results with the predictions from a grid of SSP models. Results. We find that the inner and outer scale-lengths of Type-III S0 galaxies at 0.4 &lt; z &lt; 0.6 follow compatible trends and scaling relations with those observed in local S0 galaxies as a function of the break radius, Rbreak. We do not detect any significant differences between the location of Rbreak between z ~ 0.6 and z ~ 0 for a fixed stellar mass of the object, whereas the surface brightness at the break radius μbreak is ~1.5 mag arcsec-2 dimmer in the local Universe than at z ~ 0.6 for a fixed stellar mass. We find no significant differences in the (B − R) colour between the inner and outer profiles of the Type-III S0 galaxies at 0.2 &lt; z &lt; 0.6. Conclusions. In contrast to Type-II (down-bending) profiles, the anti-truncated surface brightness profiles of S0 galaxies present compatible Rbreak values and scaling relations during the last 6 Gyr. This result and the similarity of the colours of the inner and outer discs point to a highly scalable and stable formation process, probably more related to gravitational and dynamical processes than to the evolution of stellar populations.

The intrinsic three-dimensional shape of galactic bars

We present the first statistical study on the intrinsic three-dimensional (3D) shape of a sample of 83 galactic bars extracted from the CALIFA survey. We use the galaXYZ code to derive the bar intrinsic shape with a statistical approach. The method uses only the geometric information (ellipticities and position angles) of bars and discs obtained from a multi-component photometric decomposition of the galaxy surface-brightness distributions. We find that bars are predominantly prolate-triaxial ellipsoids (68%), with a small fraction of oblate-triaxial ellipsoids (32%). The typical flattening (intrinsic C/A semiaxis ratio) of the bars in our sample is 0.34, which matches well the typical intrinsic flattening of stellar discs at these galaxy masses. We demonstrate that, for prolate-triaxial bars, the intrinsic shape of bars depends on the galaxy Hubble type and stellar mass (bars in massive S0 galaxies are thicker and more circular than those in less massive spirals). The bar intrinsic shape correlates with bulge, disc, and bar parameters. In particular with the bulge-to-total (B/T) luminosity ratio, disc g-r color, and central surface brightness of the bar, confirming the tight link between bars and their host galaxies. Combining the probability distributions of the intrinsic shape of bulges and bars in our sample we show that 52% (16%) of bulges are thicker (flatter) than the surrounding bar at 1$\sigma$ level. We suggest that these percentages might be representative of the fraction of classical and disc-like bulges in our sample, respectively.

Photometric investigations of NGC 2577 and NGC 4310 Lenticular Galaxies

In this study, two lenticular galaxies ( NGC 2577, NGC 4310 ) have been chosen to study their morphological and photometric properties, by using The [1] IRAF ISOPHOTE ELLIPSE task with griz -Filters. Observations are obtained from the Sloan Digital Sky Survey (SDSS) which are reach now to the Data Release (DR14). The data reduction of all images (bias and flat field) have been done by SDSS pipeline. The surface photometric investigations were performed like the total magnitude, together with isophotal contour maps, Surface brightness profiles and a bulge/disk decomposition of the images of the galaxies, although the disk position angle, ellipticity and inclination of the galaxies have been done. [1] IRAF is distributed by the National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.