Star complexes and stellar populations in NGC 6822 - Comparison with the Magellanic Clouds

The star complexes (large scale star forming regions) of NGC 6822 were traced and mapped and their size distribution was compared with the size distribution of star complexes in the Magellanic Clouds (MCs). Furthermore, the spatial distributions of different age stellar populations were compared with each other. The star complexes of NGC 6822 were determined by using the isopleths, based on star counts, of the young stars of the galaxy, using a statistical cutoff limit in density. In order to map them and determine their geometrical properties, an ellipse was fitted to every distinct region satisfying this minimum limit. The Kolmogorov-Smirnov statistical test was used to study possible patterns in their size distribution. Isopleths were also used to study the stellar populations of NGC 6822. The star complexes of NGC 6822 were detected and a list of their positions and sizes was produced. Indications of hierarchical star formation, in terms of spatial distribution, time evolution and preferable sizes were found in NGC 6822 and the MCs. The spatial distribution of the various age stellar populations has indicated traces of an interaction in NGC 6822, dated before 350 +/- 50 Myr.Comment: 10 pages, 7 figures, accepted by A&A; minor typeface correction

Structure of the SMC - Stellar component distribution from 2MASS data

The spatial distribution of the SMC stellar component is investigated from 2MASS data. The morphology of the different age populations is presented. The center of the distribution is calculated and compared with previous estimations. The rotation of the stellar content and possible consequence of dark matter presence are discussed. The different stellar populations are identified through a CMD diagram of the 2MASS data. Isopleth contour maps are produced in every case, to reveal the spatial distribution. The derived density profiles are discussed. The older stellar population follows an exponential profile at projected diameters of about 5 kpc (~5 deg) for the major axis and ~4 kpc for the minor axis, centred at RA: 0h:51min, Dec: -73deg 7' (J2000.0). The centre coordinates are found the same for all the different age population maps and are in good accordance with the kinematical centre of the SMC. However they are found considerably different from the coordinates of the centre of the gas distribution. The fact that the older population found on an exponential disk, gives evidence that the stellar content is rotating, with a possible consequence of dark matter presence. The strong interactions between the MCs and the MilkyWay might explain the difference in the distributions of the stellar and gas components. The lack in the observed velocity element, that implies absence of rotation, and contradicts with the consequences of exponential profile of the stellar component, may also be a result of the gravitational interactions.Comment: 7 Pages, 6 figures, accepted for publication in A&

Exploring the experiences of people vlogging about severe mental illness on YouTube: An interpretative phenomenological analysis

© 2018 Elsevier B.V. Background: Evidence suggests that, compared to the general population, individuals with severe mental illness (SMI) are more likely to engage in online social networking and share personal experiences through blogging. However, little is known about the impact of creating and publicly sharing mental health videos (vlogging) on individuals with self-identified SMIs. Aims: The present study aims to investigate the experiences of individuals with self-identified SMIs who vlog about their SMI on YouTube. Methods: YouTube was systematically searched using four key search items (“schizophrenia”, “bipolar disorder”, “major depressive disorder” and “schizoaffective disorder”). After manually screening approximately 50 channels, a set of 30 videos by individuals with self-identified SMIs discussing their experience of vlogging was selected and transcribed verbatim. An interpretative phenomenological analysis (IPA) was employed for the analysis of the data. Results: The analysis produced three global themes: Minimising Isolation; Vlogging as Therapy; and Fighting stigma. Limitations: The data collected was limited as regards depth of content by the inability to ask follow-up questions. Conclusions: The findings suggest that engaging in the act of vlogging about mental illness may benefit and encourage recovery in individuals with SMIs by providing them with peer support, enhancing self-efficacy, and reducing self-stigma. Future research should employ interviews to produce more robust data for analysis

Spatial distribution of stellar populations in the Magellanic Clouds: Implementation to Gaia

The main goal of our project is to investigate the spatial distribution of different stellar populations in the Magellanic Clouds. The results from modelling the Magellanic Clouds can be useful, among others, for simulations during the Gaia mission preparation. Isodensity contour maps have been used in order to trace the morphology of the different stellar populations and estimate the size of these structures. Moreover, star density maps are constructed through star counts and projected radial density profiles are obtained. Fitting exponential disk and King law curves to the spatial distribution allows us to derive the structural parameters that describe these profiles. The morphological structure and spatial distributions of various stellar components in the Magellanic Clouds (young and intermediate age stars, carbon stars) along with the overall spatial distribution in both Clouds are provided.Comment: 12 pages, 9 figures, to be published in Astronomy & Astrophysics; typos and language correcte

Star Formation History in two fields of the Small Magellanic Cloud Bar

The Bar is the most productive region of the Small Magellanic Cloud in terms of star formation but also the least studied one. In this paper we investigate the star formation history of two fields located in the SW and in the NE portion of the Bar using two independent and well tested procedures applied to the color-magnitude diagrams of their stellar populations resolved by means of deep HST photometry. We find that the Bar experienced a negligible star formation activity in the first few Gyr, followed by a dramatic enhancement from 6 to 4 Gyr ago and a nearly constant activity since then. The two examined fields differ both in the rate of star formation and in the ratio of recent over past activity, but share the very low level of initial activity and its sudden increase around 5 Gyr ago. The striking similarity between the timing of the enhancement and the timing of the major episode in the Large Magellanic Cloud is suggestive of a close encounter triggering star formation.Comment: 30 pages, 22 figures, accepted for publication in Ap

Spitzer Analysis of HII Region Complexes in the Magellanic Clouds: Determining a Suitable Monochromatic Obscured Star Formation Indicator

HII regions are the birth places of stars, and as such they provide the best measure of current star formation rates (SFRs) in galaxies. The close proximity of the Magellanic Clouds allows us to probe the nature of these star forming regions at small spatial scales. We aim to determine the monochromatic IR band that most accurately traces the bolometric IR flux (TIR), which can then be used to estimate an obscured SFR. We present the spatial analysis, via aperture/annulus photometry, of 16 LMC and 16 SMC HII region complexes using the Spitzer IRAC and MIPS bands. UV rocket data and SHASSA H-alpha data are also included. We find that nearly all of the LMC and SMC HII region SEDs peak around 70um, from ~10 to ~400 pc from the central sources. As a result, the sizes of HII regions as probed by 70um is approximately equal to the sizes as probed by TIR (about 70 pc in radius); the radial profile of the 70um flux, normalized by TIR, is constant at all radii (70um ~ 0.45 TIR); the 1-sigma standard deviation of the 70um fluxes, normalized by TIR, is a lower fraction of the mean (0.05 to 0.12 out to ~220 pc) than the normalized 8, 24, and 160um normalized fluxes (0.12 to 0.52); and these results are invariant between the LMC and SMC. From these results, we argue that 70um is the most suitable IR band to use as a monochromatic obscured star formation indicator because it most accurately reproduces the TIR of HII regions in the LMC and SMC and over large spatial scales. We also explore the general trends of the 8, 24, 70, and 160um bands in the LMC and SMC HII region SEDs, radial surface brightness profiles, sizes, and normalized (by TIR) radial flux profiles. We derive an obscured SFR equation that is modified from the literature to use 70um luminosity, SFR(Mo/yr) = 9.7(0.7)x10^{-44} L(70)(ergs/s), which is applicable from 10 to 300 pc distance from the center of an HII region.Comment: 21 pages, 12 figures, 4 tables. Will be published in ApJ

A systematic review of the psychometric properties, usability and clinical impacts of mobile mood-monitoring applications in young people

Background: Mobile mood-monitoring applications are increasingly used by mental health providers, widely advocated within research, and a potentially effective method to engage young people. However, little is known about their efficacy and usability in young populations. Method: A systematic review addressing 3 research questions focused on young people: 1) what are the psychometric properties of mobile mood-monitoring applications; 2) what is their usability; and 3) what are their positive and negative clinical impacts? Findings were synthesised narratively, study quality assessed, and compared with evidence from adult studies. Results: We reviewed 25 articles. Studies on the psychometric properties of mobile mood-monitoring applications were sparse, but indicate questionable to excellent internal consistency, moderate concurrent validity, and good usability. Participation rates ranged from 30-99% across studies, and appeared to be affected by methodological factors (e.g., payments) and individual characteristics (e.g., IQ score). Mobile mood-monitoring applications are positively perceived by youth, may reduce depressive symptoms by increasing emotional awareness, and could aid in the detection of mental health and substance use problems. There was very limited evidence on potential negative impacts. Conclusions: Evidence for the use of mood-monitoring applications in youth is promising but limited due to a lack of high quality studies. Future work should explicate the effects of mobile mood-monitoring applications on effective self-regulation, clinical outcomes across disorders, and young people's engagement with mental health services. Potential negative impacts in this population should also be investigated, as the adult literature suggests that application use could potentially increase negativity and depression symptoms

Age-metallicity relation in the Magellanic Clouds clusters

Aims. We study small open star clusters, using Strömgren photometry to investigate a possible dependence between age and metallicity in the Magellanic Clouds (MCs). Our goals are to trace evidence of an age metallicity relation (AMR) and correlate it with the mutual interactions of the two MCs and to correlate the AMR with the spatial distribution of the clusters. In the Large Magellanic Cloud (LMC), the majority of the selected clusters are young (up to 1 Gyr), and we search for an AMR at this epoch, which has not been much studied. Methods. We report results for 15 LMC and 8 Small Magellanic Cloud (SMC) clusters, scattered all over the area of these galaxies, to cover a wide spatial distribution and metallicity range. The selected LMC clusters were observed with the 1.54 m Danish Telescope in Chile, using the Danish Faint Object Spectrograph and Camera (DFOSC) with a single 2k × 2k CCD. The SMC clusters were observed with the ESO 3.6 m Telescope, also in Chile, using the ESO Faint Object Spectrograph and Camera (EFOSC). The obtained frames were analysed with the conventional DAOPHOT and IRAF software. We used Strömgren filters in order to achieve reliable metallicities from photometry. Isochrone fitting was used to determine the ages and metallicities. Results. The AMR for the LMC displays a metallicity gradient, with higher metallicities for the younger ages. The AMR for LMC-SMC star clusters shows a possible jump in metallicity and a considerable increase at about 6 × 108 yr. It is possible that this is connected to the latest LMC-SMC interaction. The AMR for the LMC also displays a metallicity gradient with distance from the centre. The metallicities in SMC are lower, as expected for a metal-poor host galaxy.Facultad de Ciencias Astronómicas y Geofísica