Influence of galaxy stellar mass and observed wavelength on disc breaks in S4^4G, NIRS0S, and SDSS data

Breaks in the surface brightness profiles in the outer regions of galactic discs are thought to have formed by various internal and external processes, and by studying the breaks we aim to better understand what processes are responsible for the evolution of the outer discs. We use a large well-defined sample to study how common the breaks are, and whether their properties depend on galaxy stellar mass or observed wavelength. We study radial surface brightness profiles of 753 galaxies, obtained from the $3.6 \mu m$ images of the Spitzer Survey of Stellar Structure in Galaxies (S$^4$G), and the $K_s$-band data from the Near InfraRed S0-Sa galaxy Survey (NIRS0S), covering a wide range of galaxy morphologies and stellar masses. Optical SDSS or Liverpool telescope data was used for 480 of these galaxies. We find that in low-mass galaxies the single exponential discs (Type I) are most common, and that their fraction decreases with increasing galaxy stellar mass. The fraction of down-bending (Type II) discs increases with stellar mass, possibly due to more common occurrence of bar resonance structures. The up-bending (Type III) discs are also more common in massive galaxies. The observed wavelength affects the scalelength of the disc of every profile type. Especially the scalelength of the inner disc of Type II profiles increases from infrared to u-band on average by a factor of $\sim 2.2$. Consistent with the previous studies, we find that Type II outer disc scalelengths ($h_o$) in late-type and low-mass galaxies are shorter in bluer wavelengths, possibly due to stellar radial migration populating the outer discs with old stars. In Type III discs $h_o$ are larger in the u-band, hinting to the presence of young stellar population in the outer disc. While the observed wavelength affects the disc parameters, it does not significantly affect the profile type in our sample. (Abridged)Comment: 22 pages, 16 figures. Accepted for publication in Astronomy & Astrophysic

Comparison of bar strengths in optical and near-infrared for the OSUBSGS sample

We use a gravitational bar torque method to compare bar strengths (the maximum tangential force normalized by radial force) in B and H-band images of 152 galaxies from the Ohio State University Bright Spiral Galaxy Survey. Our main motivation is to check how much the difference in the rest-frame wavelength could affect comparisons of bar strengths in low and high redshift observations. Between these two bands we find an average bar strength ratio Q_B/H= 1.25 which factor is nearly independent of the morphological type. We show that Q_B/H > 1 is mostly due to reduced bulge dilution of radial forces in the B-band. The bar torque method needs an estimate for the vertical scale height of the galaxy, based on the radial scale length of the disk and the galaxy's morphological type. Since these two might not always be possible to determine at high redshifts in a reliable manner, we also checked that similar results are obtained with vertical scale heights estimated from the radii corresponding to the K-band surface brightness of 20 mag/arcsec^2. Also, we made a simple test of the usability of the bar torque method at high redshifts by checking the effects of image degradation (nearest neighbour sampling without any adjustment of noise levels): we found that the estimated bar strengths varied by +/- 10% at most as long as the total extent of the bar was at least 10 pixels. Overall, we show that the gravitational bar torque method should provide a proficient tool for quantifying bar strengths also at high redshifts.Comment: 15 pages, 9 figures, 1 table, accepted to MNRA

Decreased Frequency of Strong Bars in S0 Galaxies: Evidence for Secular Evolution?

Using data from the Near-Infrared S0 Survey (NIRS0S) of nearby, early-type galaxies, we examine the distribution of bar strengths in S0 galaxies as compared to S0/a and Sa galaxies, and as compared to previously published bar strength data for Ohio State University Bright Spiral Galaxy Survey (OSUBSGS) spiral galaxies. Bar strengths based on the gravitational torque method are derived from 2.2 micron Ks-band images for a statistical sample of 138 (98 S0, 40 S0/a,Sa) galaxies having a mean total blue magnitude <= 12.5 and generally inclined less than 65 degrees. We find that S0 galaxies have weaker bars on average than spiral galaxies in general, even compared to their closest spiral counterparts, S0/a and Sa galaxies. The differences are significant and cannot be due entirely to uncertainties in the assumed vertical scale-heights or in the assumption of constant mass-to-light ratios. Part of the difference is likely due simply to the dilution of the bar torques by the higher mass bulges seen in S0s. If spiral galaxies accrete external gas, as advocated by Bournaud & Combes, then the fewer strong bars found among S0s imply a lack of gas accretion according to this theory. If S0s are stripped former spirals, or else are evolved from former spirals due to internal secular dynamical processes which deplete the gas as well as grow the bulges, then the weaker bars and the prevalence of lenses in S0 galaxies could further indicate that bar evolution continues to proceed during and even after gas depletionComment: Accepted for publication in the Astrophysical Journal, September 2010 issue (LaTex, 29 pages + 3 figures, uses aastex.cls

On the Role of Minor Galaxy Mergers in the Formation of Active Galactic Nuclei

The large scale (~ 100 kpc) environments of Seyfert galaxies are not significantly different from those of non-Seyfert galaxies. In the context of the interaction model of the formation of active galactic nuclei (AGN), it has been proposed that AGN form via "minor mergers" of large disk galaxies with smaller companions. We test this hypothesis by comparing the nuclear spectra of 105 bright nearby galaxies with measurements of their R or r band morphological asymmetries at three successive radii. We find no significant differences in these asymmetries between the 13 Seyfert galaxies in the sample and galaxies having other nuclear spectral types (absorption, H II-region like, LINER), nor is there strong qualitative evidence that such mergers have occured among any of the Seyferts or LINERs. Thus either any minor mergers began > 1 Gyr ago and are essentially complete, or they did not occur at all, and AGN form independently of any type of interaction. Support for the latter interpretation is provided by the growing evidence that supermassive black holes exist in the cores of most elliptical and early-type spiral galaxies, which in turn suggests that nuclear activity represents a normal phase in the evolution of the bulges of massive galaxies. Galaxy mergers may increase the luminosity of Seyfert nuclei to the level of QSOs, which could explain why the latter objects appear to be found in rich environments and in interacting systems.Comment: 13 pages, 2 figures, to appear in Astrophysical Journal Letter

Kinematics and dynamics of the M51-type galaxy pair NGC 3893/96 (KPG 302)

We study the kinematics and dynamics of the M51-type interacting galaxy pair KPG 302 (NGC 3893/96). We analyse the distribution of the dark matter (DM) halo of the main galaxy in order to explore possible differences between DM halos of "isolated" galaxies and those of galaxies belonging to a pair. The velocity field of each galaxy was obtained using scanning Fabry-Perot interferometry. A two-dimensional kinematic and dynamical analysis of each galaxy and the pair as a whole is done emphasizing the contribution of circular and non-circular velocities. Non-circular motions can be traced on the rotation curves of each galaxy allowing us to differentiate between motions associated to particular features and motions that reflect the global mass distribution of the galaxy. For the main galaxy of the pair, NGC 3893, optical kinematic information is complemented with HI observations from the literature to build a multi-wavelength rotation curve. We try to fit this curve with a mass-distribution model using different DM halos. We find that the multi-wavelength rotation curve of NGC 3893, "cleaned" from the effect of non-circular motions, cannot be fitted neither by a pseudo-isothermal nor by a NFW DM halo.Comment: Accepted for publication in A&A. 11 pages, 9 figures and 2 table

Asiakaskeskeinen liikuntapalvelukonsepti senioreille Espoon alueen liikuntakeskuksissa

Liikunnan avulla senioreiden elämään voidaan lisätä laatua ja vuosia. Hyvinvoiva ja toiminta-kykyinen seniori selviytyy arjen askareista omin avuin ja kuluttaa vähemmän terveydenhuollon resursseja. Liikuntakeskukset ruuhkautuvat iltaisin nuorista ja työssäkäyvistä, mutta senioreilla on mahdollisuus harrastaa liikuntaa päivisin. Liikuntakeskuksille seniori on mahdollisuus liiketoiminnan kasvattamiseen. Opinnäytetyö toteutettiin yhteistyössä kolmen Espoon alueen liikuntakeskuksen kanssa. Työn tarkoituksena oli selvittää millaisia liikuntapalvelutarpeita senioreilla on Espoon alueella. Tavoitteena oli tutkimustulosten perusteella muodostaa asiakaskeskeinen liikuntapalvelukonsepti senioreille liikuntakeskusten hyödynnettäväksi ja saada liikuntakeskukset huomioimaan senioreita paremmin. Tutkimus toteutettiin kvalitatiivisen tutkimusmenetelmän avulla teemahaastatteluina, koska tavoitteena oli selvittää senioreiden käyttäytymisen syvempiä merkityksiä antamatta mahdollisuutta vastata valmiiksi valikoituihin vastausvaihtoehtoihin. Tutkimuksessa käytettiin viittä eri teemaa, joiden avulla turvattiin tarvittavan tiedon saanti ja keskustelun kohdistuminen tutkimusongelman kannalta keskeisiin asioihin. Tutkimuksessa haastateltiin kahdeksaa liikuntakeskusten henkilökunnan jäsentä sekä kahtatoista asiakkaan roolissa olevaa senioria. Tutkimus osoitti, että liikunta on tärkeää senioreiden toimintakyvyn ylläpidon, yleisen hyvinvoinnin ja sosiaalisen ulottuvuuden kannalta. Seniorit nähdään potentiaalisena kohderyhmänä liikuntakeskusten asiakaskannassa. Senioreille suunnattuihin liikuntapalveluihin ei ole kiinnitetty tarpeeksi huomiota, mutta palvelujen kehittämistä pidetään tärkeänä. Liikuntapalveluiden lisäksi hyvinvointipalvelut nähdään tärkeänä osana palvelukokonaisuutta. Yksilöohjauksen merkityksen ja ryhmän tuen nähdään korostuvan erityisesti ikääntyvien ja aloittelijoiden liikunnassa. Johtopäätöksenä todetaan, että senioreille kohdennetuille liikuntapalveluille löytyy kysyntää Espoon alueella. Olemassa on suuri joukko senioreita, jotka eivät ole vielä löytäneet liikunnan iloa ja asiakaskeskeisen liikuntapalvelukonseptin avulla liikuntakeskukset voivat vaikuttaa senioreiden liikuntatottumuksiin. Tulevaisuudessa seniorit ovat tottuneempia liikuntakeskusten käyttäjiä ja valmiimpia käyttämään rahaa oman hyvinvointinsa edistämiseen. Liikuntakeskusten pikainen reagointi mahdollistaa potentiaalin kokonaisvaltaisen hyödyntämisen. Kehitysehdotuksena muodostettiin asiakaskeskeinen liikuntapalvelukonsepti, joka pitää sisällään senioreiden tarpeet huomioonottavia palveluita ja toimintatapoja. Palvelukonsepti ottaa huomioon senioreiden fyysiset, psyykkiset ja sosiaaliset tarpeet. Konseptia voidaan hyödyntää kokonaisuudessaan tai siitä voidaan poimia eri osa-alueita.Customer-centric fitness service concept for senior people in the fitness centers in Espoo By physical exercise quality and years in the lives of seniors can be increased. A well-rounded and energetic senior copes with everyday chores on his own and spends less on health care resources. A fitness center is fully booked-up with young people and the working populations in the evening, but senior people have the opportunity to exercise during the day. For fitness centers a senior is a possibility to expand the business. The thesis was executed in co-operation between the three Espoo fitness centers. The purpose was to discover what fitness and wellness service needs of senior people are in Espoo. The objective based on research results was to create a customer-centric fitness service concept for senior people and to obtain fitness centers to cater for senior people better. The study was conducted using a qualitative research method and theme interview since the objective was to examine the deeper meanings of the behavior of senior people without giving the opportunity to respond to pre-selected answer options. The interviews consisted of five different themes, which helped to secure information needed and focus conversation on the main facts of the research problem. Eight staff members of fitness centers and 12 seniors in the roles of customer were interviewed in the study. The study showed that physical activity is important for seniors to the maintenance of functional capacity, general well-being and the social dimension. Seniors are seen as a potential target group of the customer base of fitness centers. Fitness and welfare services directed for seniors have not been taken into account, but the development of services is considered important. Physical exercise in addition to welfare services are seen as an important part of a service package. The importance of Individual guidance and group support is being emphasized especially in the exercise of aging people and beginners. It can be concluded that there is demand for fitness services for senior people in Espoo. There is a large group of seniors who have not yet found the pleasure of exercise and the help of fitness and welfare concept fitness centers could affect seniors’ physical activity. In the future seniors will be more familiar with fitness centers and they will spend more money to promote their own well being. The exploitation of maximum potential is made possible by a quick reaction of fitness centers. The customer-centric fitness concept was formed as a development proposal. The concept encompasses the needs of senior-friendly services and ways of action. The service concept takes into account seniors’ physical, psychological and social needs. The concept can be utilized in its entirety or it can be implemented in parts

The stellar mass distribution of S4^{4}G disk galaxies

We use 3.6 $\mu$m imaging from the S$^{4}$G survey to characterize the typical stellar density profiles ($\Sigma_{\ast}$) and bars as a function of fundamental galaxy parameters (e.g. the total stellar mass $M_{\ast}$), providing observational constraints for galaxy simulation models to be compared with. We rescale galaxy images to a common frame determined by the size in physical units, by their disk scalelength, or by their bar size and orientation. We stack the resized images to obtain statistically representative average stellar disks and bars. For a given $M_{\ast}$ bin ($\ge 10^{9}M_{\odot}$), we find a significant difference in the stellar density profiles of barred and non-barred systems that gives evidence for bar-induced secular evolution of disk galaxies: (i) disks in barred galaxies show larger scalelengths and fainter extrapolated central surface brightnesses, (ii) the mean surface brightness profiles of barred and non-barred galaxies intersect each other slightly beyond the mean bar length, most likely at the bar corotation, and (iii) the central mass concentration of barred galaxies is larger (by almost a factor 2 when $T<5$) than in their non-barred counterparts. We also show that early- and intermediate-type spirals ($0 \le T < 5$) host intrinsically narrower bars than the later types and S0s, whose bars are oval-shaped. We show a clear correlation between galaxy family and bar ellipticity.Comment: Proceedings of IAU Symposium 321, "Formation and evolution of galaxy outskirts", Eds. A. Gil de Paz, J. C. Lee & J. H. Knapen, Cambridge University Press, Cambridg

On the nature of the barlens component in barred galaxies: what do boxy/peanut bulges look like when viewed face-on?

Barred galaxies have interesting morphological features whose presence and properties set constraints on galactic evolution. Here we examine barlenses, i.e. lens-like components whose extent along the bar major axis is shorter than that of the bar and whose outline is oval or circular. We identify and analyse barlenses in $N$-body plus SPH simulations, compare them extensively with those from the NIRS0S (Near-IR S0 galaxy survey) and the S$^4$G samples (Spitzer Survey of Stellar Structure in Galaxies) and find very good agreement. We observe barlenses in our simulations from different viewing angles. This reveals that barlenses are the vertically thick part of the bar seen face-on, i.e. a barlens seen edge-on is a boxy/peanut/X bulge. In morphological studies, and in the absence of kinematics or photometry, a barlens, or part of it, may be mistaken for a classical bulge. Thus the true importance of classical bulges, both in numbers and mass, is smaller than currently assumed, which has implications for galaxy formation studies. Finally, using the shape of the isodensity curves, we propose a rule of thumb for measuring the barlens extent along the bar major axis of moderately inclined galaxies, thus providing an estimate of which part of the bar is thicker.Comment: 21 pages, 11 figures, revised version as published in MNRA

Catalogue of the morphological features in the Spitzer Survey of Stellar Structure in Galaxies (S4^4G)

A catalogue of the morphological features for the complete Spitzer Survey of Stellar Structure in Galaxies (S$^4$G), including 2352 nearby galaxies, is presented. The measurements are made using 3.6 $\mu$m images, largely tracing the old stellar population; at this wavelength the effects of dust are also minimal. The measured features are the sizes, ellipticities, and orientations of bars, rings, ringlenses, and lenses. Measured in a similar manner are also barlenses (lens-like structures embedded in the bars), which are not lenses in the usual sense, being rather the more face-on counterparts of the boxy/peanut structures in the edge-on view. In addition, pitch angles of spiral arm segments are measured for those galaxies where they can be reliably traced. More than one pitch angle may appear for a single galaxy. All measurements are made in a human-supervised manner so that attention is paid to each galaxy. We used isophotal analysis, unsharp masking, and fitting ellipses to measured structures. We find that the sizes of the inner rings and lenses normalized to barlength correlate with the galaxy mass: the normalized sizes increase toward the less massive galaxies; it has been suggested that this is related to the larger dark matter content in the bar region in these systems. Bars in the low mass galaxies are also less concentrated, likely to be connected to the mass cut-off in the appearance of the nuclear rings and lenses. We also show observational evidence that barlenses indeed form part of the bar, and that a large fraction of the inner lenses in the non-barred galaxies could be former barlenses in which the thin outer bar component has dissolved.Comment: 17 pages, 12 figures, accepted for publication in A&