Search

Contemporary research suggests that the reionisation of the intergalactic medium (IGM) in the early Universe was predominantly realised by star-forming (proto-)galaxies (SFGs). Due to observational constraints, our knowledge on the origins of sufficient amounts of ionising Lyman continuum (LyC) photons and the mechanisms facilitating their transport into the IGM remains sparse. Recent efforts have thus focussed on the study of local analogues to these high-redshift objects. We used archival spectroscopic SDSS DR12 data to select a sample of low-z He II 4686 emitters and restricted it to a set of SFGs with an emission line diagnostic sensitive to the presence of an AGN, which serves as our only selection criterion. Our final sample consists of eighteen low-mass, low-metallicity dwarf galaxies which appear to be predominantly ionised by stellar sources. We find large O32 ratios and [S II] deficiencies, which provide strong indications for these galaxies to be LyC Emitters (LCEs). At least 40% of these objects are candidates for featuring cosmologically significant LyC escape fractions >10%. Their SFHs exhibit strong similarities and almost all galaxies appear to contain an old (>1 Gyr) stellar component, while also harbouring a young, two-stage (~10 Myr and, 28 pages, 22 figures. Accepted for publication in Astronomy & Astrophysics

Context. The existence of magnetic fields in the circumgalactic medium (CGM) is largely unconstrained. Their detection is important as magnetic fields can have a significant impact on the evolution of the CGM and, in turn, the fields can serve as tracers for dynamical processes in the CGM. Aims. With Faraday rotation of polarised background sources, we aim to detect a possible excess of the rotation measure in the surrounding area of nearby galaxies. Methods. We use 2,461 residual rotation measures (RRMs) observed with the LOw Frequency ARray (LOFAR), where the foreground contribution from the Milky Way is subtracted. The RRMs are then studied around a subset of 183 nearby galaxies that was selected by apparent $B$-band magnitude. Results. We find that, in general, the RRMs show no significant excess for small impact parameters (i.e. the perpendicular distance to the line of sight). However, if we only consider galaxies at higher inclination angles and sight lines that pass close to the minor axis of the galaxies, we find significant excess at impact parameters of less than 100 kpc. The excess in |RRM| is 3.7 $\rm rad\,m^{-2}$ with an uncertainty between $\pm 0.9~\rm rad\,m^{-2}$ and $\pm 1.3~\rm rad\,m^{-2}$ depending on the statistical properties of the background (2.8$\sigma$-4.1$\sigma$). With electron densities of ~$10^{-4}~\rm cm^{-3}$ this suggests magnetic field strengths of a few tenths of a micro Gauss. Conclusions. Our results suggest a slow decrease of the magnetic field strength with distance from the galactic disc such as expected if the CGM is magnetised by galactic winds and outflows., Comment: 5 pages, 4 figures, accepted as Letter to Astronomy and Astrophysics

Weakly interacting massive particles (WIMPs) can self-annihilate, thus providing us with a way to indirectly detect dark matter (DM). Dwarf spheroidal (dSph) galaxies are excellent places to search for annihilation signals because they are rich in DM and background emission is low. If magnetic fields in dSph galaxies exist, the particles produced in DM annihilation emit synchrotron radiation. We used the non-detection of 150 MHz radio continuum emission from dSph galaxies with the LOw Frequency ARray (LOFAR) to derive constraints on the annihilation cross section of WIMPs in electron-positron pairs. Our main underlying assumption is that the transport of the cosmic rays can be described by the diffusion approximation, which necessitates the existence of magnetic fields. We used observations of six dSph galaxies in the LOFAR Two-metre Sky Survey (LoTSS). The data were reimaged and radial profiles were generated. We also used stacking to increase the sensitivity. In order to derive upper limits on the WIMP cross section, we injected fake Gaussian sources into the data, which were then detected with 2$\sigma$ significance in the radial profile. These sources represent the lowest emission we would have been able to detect. We present limits from the observations of individual galaxies as well as from stacking. We explored the uncertainty due to the choice of diffusion and magnetic field parameters by constructing three different model scenarios: optimistic (OPT), intermediate (INT), and pessimistic (PES). Assuming monochromatic annihilation into electron-positron pairs, the limits from the INT scenario exclude thermal WIMPs below 20 GeV, and the limits from the OPT scenario even exclude thermal WIMPs below 70 GeV. The INT limits can compete with limits set by Fermi-LAT using $\gamma$-ray observations of multiple dwarf galaxies, and they are especially strong for low WIMP masses., Comment: 15 pages, 10 figures

The Low Frequency Array (LOFAR) is the only existing radio interferometer able to observe at ultra-low frequencies (, 20 pages, 22 figures, images and catalogues available at https://www.lofar-surveys.org/lolss.html

Galactic winds play a key role in regulating the evolution of galaxies over cosmic time. In recent years, the role of cosmic rays (CR) in the formation of the galactic wind has increasingly gained attention. Therefore, we use radio continuum data to analyse the cosmic ray transport in edge-on galaxies. Data from the LOFAR Two-metre Sky Survey (LoTSS) data release 2 at 144 MHz (HBA) and reprocessed VLA data at 1.6 GHz (L-band) from the Continuum Halos in Nearby Galaxies - an EVLA Survey (CHANG-ES) enable us to increase the extent of the analysed radio continuum profile significantly (up to a factor of 2) compared to previous studies. We compute thermal emission maps using a mixture approach of H-alpha and near infrared data, which is then subtracted to yield radio synchrotron emission maps. Then we compile non-thermal spectral index maps and compute intensity profiles using a box integration approach. Lastly, we perform 1D cosmic ray transport modelling. The non-thermal spectral index maps show evidence that the LoTSS maps are affected by thermal absorption, in star forming regions. The scale height analysis reveals that most of the galaxies are equally well fitted with an one-component instead of a twocomponent exponential profile. We find a bi-modality within our sample. While NGC 3432 and NGC 4013 have similar scale heights in the L-band and HBA, the low-frequency scale heights of NGC 891, NGC 4157, and NGC 4631 exceed their high-frequency counterpart significantly. The 1D CR transport modelling shows agreement of the predicted magnetic field strength and the magnetic field strength estimates of equipartition measurements. Additionally we find an increasing difference of wind velocities (with increasing height over the galactic disk) between central and outer regions of the analysed galaxies., Accepted for publication in Astronomy & Astrophysics section 4. Extragalactic astronomy

Context. Cosmic rays and magnetic fields are key ingredients in galaxy evolution, regulating both stellar feedback and star formation. Their properties can be studied with low-frequency radio continuum observations that are free from thermal contamination. Aims. We define a sample of 76 nearby (< 30 Mpc) galaxies with rich ancillary data in the radio continuum and infrared from the CHANG-ES and KINGFISH surveys, which will be observed with the LOFAR Two-metre Sky Survey (LoTSS) at 144 MHz. Methods. We present maps for 45 of them as part of the LoTSS data release 2 (LoTSS-DR2), where we measure integrated flux densities and study integrated and spatially resolved radio spectral indices. We investigate the radio–star formation rate (SFR) relation using SFRs derived from total infrared and Hα + 24-μm emission. Results. The radio–SFR relation at 144 MHz is clearly super-linear with L144 MHz ∝ SFR1.4−1.5. The mean integrated radio spectral index between 144 and ≈1400 MHz is ⟨α⟩= − 0.56 ± 0.14, in agreement with the injection spectral index for cosmic ray electrons (CREs). However, the radio spectral index maps show variation of spectral indices with flatter spectra associated with star-forming regions and steeper spectra in galaxy outskirts and, in particular, in extra-planar regions. We found that galaxies with high SFRs have steeper radio spectra; we find similar correlations with galaxy size, mass, and rotation speed. Conclusions. Galaxies that are larger and more massive are better electron calorimeters, meaning that the CRE lose a higher fraction of their energy within the galaxies. This explains the super-linear radio–SFR relation, with more massive, star-forming galaxies being radio bright. We propose a semi-calorimetric radio–SFR relation that employs the galaxy mass as a proxy for the calorimetric efficiency.

Context. State of the art simulations of astrospheres are modelled using three-dimensional (3D) magnetohydrodynamics (MHD). An astrospheric interaction of a stellar wind (SW) with its surrounding interstellar medium (ISM) can only generate a bow shock if the speed of the interstellar inflow is higher than the fast magnetosonic speed. Aims. The differences of astrospheres at differing speeds of the ISM inflow are investigated, and the necessity of the third dimension in modelling is evaluated. Methods. The model astrosphere of the runaway O-star $\lambda$ Cephei is computed in both two- and three-dimensional MHD at four different ISM inflow speeds, one of which is barely faster (superfast) and one of which is slower (subfast) than the fast magnetosonic speed. Results. The two-dimensional (2D) and 3D models of astrospheres with ISM inflow speeds considerably higher than the fast magnetosonic speed are in good agreement. However, in 2D models, where no realistic SW magnetic field can be modelled, the downwind structures of the astrospheres vacillate. Models where hydrodynamic effects are not clearly dominant over the magnetic field show asymmetries, thus necessitating a 3D approach. The physical times of simulations of astrospheres with slow ISM inflows can swiftly exceed the lifetime of the corresponding star. A hitherto unobserved structure has been found downwind of the astrotail in the subfast 3D model., Comment: 11 pages, 6 figures

Context. Three-dimensional models of astrospheres have recently become of interest. However, comparisons between these models and observations are non-trivial because of the two-dimensional nature of observations. Aims. By projecting selected physical values of three-dimensional models of astrospheres onto the surface of a sphere that is centred on a virtual all-sky observer, these models can be compared to observational data in different observables: the column density, bremsstrahlung flux, rotation measure, Hα flux, and synchrotron or cyclotron flux. Methods. Projections were calculated by rotating and moving the astrosphere model to the desired position and orientation and by then computing the value of a given patch on the sphere by a modified line-of-sight integration. Contributions to the selected observable made by all model cells that are connected to the patch by the line of sight in question were taken into account. Results. When the model produces a bow shock, a distinct parabolic structure produced by the outer astrosheath can be seen in every observable of the projection, the exact shape depending on the orientations of the line of sight and the stellar motion. Of all four examined astrosphere models, only that of λ Cephei shows fluxes that are higher than current observational thresholds. This is due to the strong stellar wind and interstellar inflow of the λ Cephei model.

We present $^{12}$CO(1-0) and $^{12}$CO(2-1) observations of a sample of 20 star-forming dwarfs selected from the Herschel Virgo Cluster Survey, with oxygen abundances ranging from 12 + log(O/H) ~ 8.1 to 8.8. CO emission is observed in ten galaxies and marginally detected in another one. CO fluxes correlate with the FIR 250 $\mu$m emission, and the dwarfs follow the same linear relation that holds for more massive spiral galaxies extended to a wider dynamical range. We compare different methods to estimate H2 molecular masses, namely a metallicity-dependent CO-to-H2 conversion factor and one dependent on H-band luminosity. The molecular-to-stellar mass ratio remains nearly constant at stellar masses, Comment: 19 pages, 11 figures, accepted for publication in Astronomy & Astrophysics

Based on a combined analysis of SDSS imaging and CALIFA integral field spectroscopy data, we report on the detection of faint (24, This paper is based on data from the Calar Alto Legacy Integral Field Area Survey, CALIFA (http://califa.caha.es), funded by the Spanish Ministery of Science under grant ICTS-2009-10, and the Centro Astronomico Hispano-Aleman. J.M.G. acknowledges support by Fundacao para a Ciencia e a Tecnologia (FCT) through the Fellowship SFRH/BPD/66958/2009 and POPH/FSE (EC) by FEDER funding through the program Programa Operacional de Factores de Competitividade (COMPETE). P.P. is supported by FCT through the Investigador FCT Contract No. IF/01220/2013 and POPH/FSE (EC) by FEDER funding through the program COMPETE. J.M.G. and P.P. acknowledge support by FCT under project FCOMP-01-0124-FEDER-029170 (Ref. PTDC/FIS-AST/3214/2012), funded by FCT-MEC (PIDDAC) and FEDER (COMPETE) and the exchange programme >Study of Emission-Line Galaxies with Integral-Field Spectroscopy> (SELGIFS, FP7-PEOPLE-2013-IRSES-612701), funded by the EU through the IRSES scheme. S.F.S. acknowledges support from CONACyT-180125 and PAPIIT-IA100815 grants. Support for L.G. is provided by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. L.G. acknowledges support by CONICYT through FONDECYT grant 3140566. C.J.W. acknowledges support through the Marie Curie Career Integration Grant 303912. I.M. acknowledges financial support by the Junta de Andalucia through project TIC114, and the Spanish Ministry of Economy and Competitiveness (MINECO) through projects AYA2010-15169 and AYA2013-42227-P. R.A. Marino is funded by the Spanish program of International Campus of Excellence Moncloa (CEI). This research made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

CALIFA is the first legacy survey being performed at Calar Alto. The CALIFA collaboration would like to thank the IAA-CSIC and MPIA-MPG as major partners of the observatory, and CAHA itself, for the unique access to telescope time and support in manpower and infrastructures. The CALIFA collaboration thanks also the CAHA staff for the dedication to this project. R.G.B., R.G.D., and E.P. are supported by the Spanish Ministerio de Ciencia e Innovacion under grant AYA2010-15081. S.Z. is supported by the EU Marie Curie Integration Grant "SteMaGE" Nr. PCIG12-GA-2012-326466 (Call Identifier: FP7-PEOPLE-2012 CIG). J.F.B. acknowledges support from grants AYA2010-21322-C03-02 and AIB-2010-DE-00227 from the Spanish Ministry of Economy and Competitiveness (MINECO), as well as from the FP7 Marie Curie Actions of the European Commission, via the Initial Training Network DAGAL under REA grant agreement number 289313. Support for L.G. is provided by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC12009, awarded to The Millennium Institute of Astrophysics, M.A.S.L.G. also acknowledges support by CONICYT through FONDECYT grant 3140566. A.G. acknowledges support from the FP7/2007-2013 under grant agreement n. 267251 (AstroFIt). J.M.G. acknowledges support from the Fundacao para a Ciencia e a Tecnologia (FCT) through the Fellowship SFRH/BPD/66958/2009 from FCT (Portugal) and research grant PTDC/FIS-AST/3214/2012. RAM was funded by the Spanish programme of International Campus of Excellence Moncloa (CEI). J.M.A. acknowledges support from the European Research Council Starting Grant (SEDmorph; P.I. V. Wild). I.M., J.M. and A.d.O. acknowledge the support by the projects AYA2010-15196 from the Spanish Ministerio de Ciencia e Innovacion and TIC 114 and PO08-TIC-3531 from Junta de Andalucia. AMI acknowledges support from Agence Nationale de la Recherche through the STILISM project (ANR-12-BS05-0016-02). M.M. acknowledges financial support from AYA2010-21887-C04-02 from the Ministerio de Economia y Competitividad. P.P. is supported by an FCT Investigador 2013 Contract, funded by FCT/MCTES (Portugal) and POPH/FSE (EC). P.P. acknowledges support by FCT under project FCOMP-01-0124-FEDER-029170 (Reference FCT PTDC/FIS-AST/3214/2012), funded by FCT-MEC (PIDDAC) and FEDER (COMPETE). T.R.L. thanks the support of the Spanish Ministerio de Educacion, Cultura y Deporte by means of the FPU fellowship. PSB acknowledges support from the Ramon y Cajal program, grant ATA2010-21322-C03-02 from the Spanish Ministry of Economy and Competitiveness (MINECO). C.J.W. acknowledges support through the Marie Curie Career Integration Grant 303912. V.W. acknowledges support from the European Research Council Starting Grant (SEDMorph P.I. V. Wild) and European Career Re-integration Grant (Phiz-Ev P.I.V. Wild). Y.A. acknowledges financial support from the Ramon y Cajal programme (RyC-2011-09461) and project AYA2013-47742-C4-3-P, both managed by the Ministerio de Economia y Competitividad, as well as the "Study of Emission-Line Galaxies with Integral-Field Spectroscopy" (SELGIFS) programme, funded by the EU (FP7-PEOPLE-2013-IRSES-612701) within the Marie-Sklodowska-Curie Actions scheme. We thank the referee David Wilman for very useful comments that improved the presentation of the paper., This paper describes the Second Public Data Release (DR2) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. The data for 200 objects are made public, including the 100 galaxies of the First Public Data Release (DR1). Data were obtained with the integral-field spectrograph PMAS/PPak mounted on the 3.5 m telescope at the Calar Alto observatory. Two different spectral setups are available for each galaxy, (i) a lowresolution V500 setup covering the wavelength range 3745–7500 Å with a spectral resolution of 6.0 Å (FWHM); and (ii) a medium-resolution V1200 setup covering the wavelength range 3650–4840 Å with a spectral resolution of 2.3 Å (FWHM). The sample covers a redshift range between 0.005 and 0.03, with a wide range of properties in the color–magnitude diagram, stellar mass, ionization conditions, and morphological types. All the cubes in the data release were reduced with the latest pipeline, which includes improved spectrophotometric calibration, spatial registration, and spatial resolution. The spectrophotometric calibration is better than 6% and the median spatial resolution is 200 : 4. In total, the second data release contains over 1.5 million spectra., Instituto de Salud Carlos III Spanish Government AYA2010-15081 AYA2010-15196, European Union (EU) PCIG12-GA-2012-326466, Spanish Ministry of Economy and Competitiveness (MINECO) AYA2010-21322-C03-02 AIB-2010-DE-00227, FP7 Marie Curie Actions of the European Commission, via the Initial Training Network DAGAL under REA 289313, Ministry of Economy, Development, and Tourism's Millennium Science Initiative IC12009, Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 3140566, Fundacao para a Ciencia e a Tecnologia (FCT) from FCT (Portugal) SFRH/BPD/66958/2009, Spanish programme of International Campus of Excellence Moncloa (CEI), European Research Council (ERC), Junta de Andalucia TIC 114 PO08-TIC-3531, French National Research Agency (ANR) ANR-12-BS05-0016-02, Spanish Government AYA2010-21887-C04-02, FCT Investigador Contract - FCT/MCTES (Portugal), European Commission Joint Research Centre European Social Fund (ESF), FCT - FCT-MEC (PIDDAC) FCOMP-01-0124-FEDER-029170 FCT PTDC/FIS-AST/3214/2012, European Union (EU), Spanish Ministerio de Educacion, Cultura y Deporte by FPU, Ramon y Cajal program from the Spanish Ministry of Economy and Competitiveness (MINECO) ATA2010-21322-C03-02, European Union (EU) 303912, European Career Re-integration Grant, Spanish Government RyC-2011-09461 AYA2013-47742-C4-3-P, European Union (EU) FP7-PEOPLE-2013-IRSES-612701, PTDC/FIS-AST/3214/2012, Science & Technology Facilities Council (STFC) ST/K000985/1

Based on the detection of C IV absorption in five Large Magellanic Cloud (LMC) stars observed with the Goddard High-Resolution Spectrograph on the Hubble Space Telescope, we present the first unambiguous evidence that C+ 3 exists in the LMC away from regions where it could have been locally produced. We can exclude that this C+ 3 is associated with hot early-type stars or active regions. Significant differences between the Hα and C+ 3 velocities toward our probes indicate that H+ and C+ 3 are not cospatial. Large column density variations show that the distribution of C+ 3 is not uniform. The properties of the LMC C IV lines are similar but not identical to those found for the Milky Way: 45 km s−1 versus 73 km s−1 for the average FWHM, (8-12) × 1013 cm−2 versus (9-16) × 1013 cm−2 for the average column density. The Hα versus C IV velocity differences and the similarity of the properties of the LMC and Milky Way C IV absorption suggest that at least some of the C+ 3 in the LMC is in a hot corona and that it has been produced by processes similar to those in the Milky Way. Our results show the feasibility of detecting high-ionization absorption in faint LMC stars, but more observations will be necessary before we can understand the distribution and properties of 105 K gas in the LMC.

Astronomy and Astrophysics 561 (2014): A129 reproduced with permission from Astronomy & Astrophysics, Context. Over the past decade, 3D optical spectroscopy has become the preferred tool for understanding the properties of galaxies and is now increasingly used to carry out galaxy surveys. Low redshift surveys include SAURON, DiskMass, ATLAS3D, PINGS, and VENGA. At redshifts above 0.7, surveys such as MASSIV, SINS, GLACE, and IMAGES have targeted the most luminous galaxies to study mainly their kinematic properties. The on-going CALIFA survey (z ~ 0.02) is the first of a series of upcoming integral field spectroscopy (IFS) surveys with large samples representative of the entire population of galaxies. Others include SAMI and MaNGA at lower redshift and the upcoming KMOS surveys at higher redshift. Given the importance of spatial scales in IFS surveys, the study of the effects of spatial resolution on the recovered parameters becomes important. Aims. We explore the capability of the CALIFA survey and a hypothetical higher redshift survey to reproduce the properties of a sample of objects observed with better spatial resolution at lower redshift. Methods. Using a sample of PINGS galaxies, we simulated observations at different redshifts. We then studied the behaviour of different parameters as the spatial resolution degrades with increasing redshift. Results. We show that at the CALIFA resolution, we are able to measure and map common observables in a galaxy study: the number and distribution of H ii regions (Hα flux structure), the gas metallicity (using the O3N2 method), the gas ionization properties (through the [N ii]/Hα and [O iii]/Hβ line ratios), and the age of the underlying stellar population (using the D4000 index). This supports the aim of the survey to characterise the observable properties of galaxies in the Local Universe. Our analysis of simulated IFS data cubes at higher redshifts highlights the importance of the projected spatial scale per spaxel as the most important figure of merit in the design of an integral field survey., Financial support from the Mexican National Council for Science and Technology (CONACYT) under the programme Estancias Posdoctorales y Sabáticas al Extranjero para la Consolidación de Grupos de Investigación, 2010-2012. I.M. financial support from the Spanish MINECO grant AYA 2010-15169, and from Junta de Andalucía TIC114 and Proyecto de Excelencia P08-TIC-03531; J.F.-B. from the Ramón y Cajal Program, grants AYA2010-21322-C03-02 and AIB-2010-DE-00227 from the Spanish Ministry of Economy and Competitiveness (MINECO), as well as from the FP7 Marie Curie Actions of the European Commission, via the Initial Training Network DAGAL under REA grant agreement na 289313. Support through the Marie Curie Career Integration Grant 303912. Support from the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA2010-21322-C03-02. This work has been partially funded by the Spanish PNAYA, project AYA2010-21887 of the Spanish MINECO. R.A. Marino was also funded by the Spanish Programme of International Campus of Excellence Moncloa (CEI).

The OB association LH 47 inside the superbubble N 44 in the Large Magellanic Cloud (LMC) is analyzed with CCD photometry. For the bright blue stars spectra in the optical and UV have been taken. The observed U , B , and V magnitudes and colours are converted to and L . From isochrone fits to the colour magnitude diagram (CMD), we find an age of the association of about 5 to 6 Myr. The stellar population outside the shell is of similar age, so there is no direct evidence for sequential star formation. The slope of the luminosity function () agrees with what has been found for other young associations. We compare two methods to derive the slope of the initial mass function (IMF). First we count all stars along the main sequence in the BV CMD. Second we count the stars between stellar evolutionary tracks in the Hertzsprung-Russell diagram (HRD). Both methods give mainly the same result, i.e. and , respectively. The IMF of the stars outside the shell shows a slightly steeper slope than inside the shell. The slope of the IMF is very similar to values found for other associations and open clusters as well as in the solar neighborhood, thus supporting the idea of an universal shape of the IMF. LH 47 turns out to be a well behaved young association embedded in a molecular cloud.

The potential role of magnetic fields and cosmic ray propagation for feedback processes in the early Universe can be probed by studies of local starburst counterparts with an equivalent star-formation rate. Archival data from the WSRT was reduced and a new calibration technique introduced to reach the high dynamic ranges needed for the complex source morphology of M82. This data was combined with archival VLA data, yielding total power maps at 3cm, 6cm, 22cm and 92cm. The data shows a confinement of the emission at wavelengths of 3/6cm to the core region and a largely extended halo reaching up to 4kpc away from the galaxy midplane at wavelengths of 22/92cm up to a sensitivity limit of 90muJy and 1.8mJy respectively. The results are used to calculate the magnetic field strength in the core region to 98muG and to 24muG in the halo regions. From the observation of free-free losses the filling factor of the ionised medium could be estimated to 2%. We find that the radio emission from the core region is dominated by very dense HII-regions and supernova remnants, while the surrounding medium is filled with hot X-ray and neutral gas. Cosmic rays radiating at frequencies higher than 1.4 GHz are suffering from high synchrotron and inverse Compton losses in the core region and are not able to reach the halo. Even the cosmic rays radiating at longer wavelengths are only able to build up the observed kpc sized halo, when several starbursting periods are assumed where the photon field density varies by an order of magnitude. These findings together with the strong correlation between Halpha, PAH+, and our radio continuum data suggests a magnetic field which is frozen into the ionised medium and driven out of the galaxy kinematically., Comment: 17 pages, 17 figures, to be published in A&A

As part of the CALIFA survey, we conducted a thorough 2D analysis of the ionized gas in two E/S0 galaxies, NGC6762 and NGC5966, aiming to shed light on the nature of their warm ionized ISM. We present optical IFS obtained with the PMAS/PPAK spectrophotometer. To recover the nebular lines, we subtracted the underlying stellar continuum from the observed spectra using the STARLIGHT code. In NGC6762, the ionized gas and stellar emission display similar morphologies, while the emission line morphology is elongated in NGC5966, spanning ~6 kpc, and is oriented roughly orthogonal to the major axis of the stellar continuum ellipsoid. Whereas gas and stars are kinematically aligned in NGC6762, the gas is kinematically decoupled from the stars in NGC5966. A decoupled rotating disk or an ionization cone are two possible interpretations of the elongated ionized gas structure in NGC5966. The latter would be the first ionization cone of such a dimension detected within a weak emission-line galaxy. Both galaxies have weak emission-lines relative to the continuum [EW(Ha)< 3 A] and have low excitation, log([OIII]5007/Hb) < 0.5. Based on optical diagnostic ratios ([OIII]5007/Hb,[NII]6584/Ha,[SII]6717,6731/Ha,[OI]6300/Ha), both objects contain a LINER nucleus and an extended LINER-like gas emission. The emission line ratios do not vary significantly with radius or aperture, which indicates that the nebular properties are spatially homogeneous. The gas emission in NGC6762 can be best explained by photoionization by pAGB stars without the need of invoking any other excitation mechanism. In the case of NGC5966, the presence of a nuclear ionizing source seems to be required to shape the elongated gas emission feature in the ionization cone scenario, although ionization by pAGB stars cannot be ruled out.(abridged), 16 pages, 13 figures, accepted for publication in A&A

Acknowledgements. We thank the referee Eric Emsellem for his detailed comments which helped to improve the content and presentation of the article. We thank the director of CEFCA, Dr. M. Moles, for his sincere support to this project. We thank the Viabilidad, Diseno, Acceso y Mejora funding program, ICTS-2009-10, and the Plan Nacional de Investigación y Desarrollo funding program, AYA2010-22111-C03-03, of the Spanish Ministerio de Ciencia e Innovacion, for the support given to this project. I.M. and J.M. acknowledge financial support from the Spanish grant AYA2010-15169 and Junta de Andalucía TIC114 and Excellence Project P08-TIC-03531. C.K., as a Humboldt Fellow, acknowledges support from the Alexander von Humboldt Foundation, Germany. B. Jungwiert acknowledges support by the grants AV0Z10030501 (Academy of Sciences of the Czech Republic) and LC06014 (Center for Theoretical Astrophysics, Czech Ministry of Education). T. Bartáková acknowledges support by the grants No. 205/08/H005 (Czech Science Foundation) and MUNI/A/0968/2009 (Masaryk University in Brno). Polychronis Papaderos is supported by a Ciencia 2008 contract, funded by FCT/MCTES (Portugal) and POPH/FSE (EC). This paper makes use of the Sloan Digital Sky Survey data. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-PlanckInstitute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington., The final product of galaxy evolution through cosmic time is the population of galaxies in the local universe. These galaxies are also those that can be studied in most detail, thus providing a stringent benchmark for our understanding of galaxy evolution. Through the huge success of spectroscopic single-fiber, statistical surveys of the Local Universe in the last decade, it has become clear, however, that an authoritative observational description of galaxies will involve measuring their spatially resolved properties over their full optical extent for a statistically significant sample. We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey, which has been designed to provide a first step in this direction. We summarize the survey goals and design, including sample selection and observational strategy. We also showcase the data taken during the first observing runs (June/July 2010) and outline the reduction pipeline, quality control schemes and general characteristics of the reduced data. This survey is obtaining spatially resolved spectroscopic information of a diameter selected sample of ~600 galaxies in the Local Universe (0.005 < z < 0.03). CALIFA has been designed to allow the building of two-dimensional maps of the following quantities: (a) stellar populations: ages and metallicities; (b) ionized gas: distribution, excitation mechanism and chemical abundances; and (c) kinematic properties: both from stellar and ionized gas components. CALIFA uses the PPAK integral field unit (IFU), with a hexagonal field-of-view of ~1.3⎕′, with a 100% covering factor by adopting a three-pointing dithering scheme. The optical wavelength range is covered from 3700 to 7000 Å, using two overlapping setups (V500 and V1200), with different resolutions: R ~ 850 and R ~ 1650, respectively. CALIFA is a legacy survey, intended for the community. The reduced data will be released, once the quality has been guaranteed. The analyzed data fulfillthe expectations of the original observing proposal, on the basis of a set of quality checks and exploratory analysis: (i) the final datacubes reach a 3σ limiting surface brightness depth of ~23.0 mag/arcsec2 for the V500 grating data (~22.8 mag/arcsec2 for V1200); (ii) about ~70% of the covered field-of-view is above this 3σ limit; (iii) the data have a blue-to-red relative flux calibration within a few percent in most of the wavelength range; (iv) the absolute flux calibration is accurate within ~8%with respect to SDSS; (v) the measured spectral resolution is ~85 km s-1 for V1200 (~150 km s-1 for V500); (vi) the estimated accuracy of the wavelength calibration is ~5 km s-1 for the V1200 data (~10 km s-1 for the V500 data); (vii) the aperture matched CALIFA and SDSS spectra are qualitatively and quantitatively similar. Finally, we show that we are able to carry out all measurements indicated above, recovering the properties of the stellar populations, the ionized gas andthe kinematics of both components. The associated maps illustrate the spatial variation of these parameters across the field, reemphasizing the redshift dependence of single aperture spectroscopic measurements. We conclude from this first look at the data that CALIFA will be an important resource for archaeological studies of galaxies in the Local Universe., CEFCA, Viabilidad, Diseno, Acceso y Mejora ICTS-2009-10, Instituto de Salud Carlos III Spanish Government AYA2010-22111-C03-03, Spanish grant AYA2010-15169, Junta de Andalucia TIC114, Excellence Project P08-TIC-03531, Alexander von Humboldt Foundation, Czech Academy of Sciences AV0Z10030501, Center for Theoretical Astrophysics, Czech Ministry of Education LC06014, Grant Agency of the Czech Republic 205/08/H005, Masaryk University in Brno MUNI/A/0968/2009, Ciencia 2008 contract, Portuguese Foundation for Science and Technology, European Commission Joint Research Centre, European Social Fund (ESF), Alfred P. Sloan Foundation, National Science Foundation (NSF), United States Department of Energy (DOE), National Aeronautics & Space Administration (NASA), Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT), Max Planck Society Foundation CELLEX, Higher Education Funding Council for England, Science & Technology Facilities Council (STFC) ST/H00243X/1 ST/J001538/1 ST/H004912/1

Observations of group and cluster galaxies reveal a large variety of interactions between galaxies and with the surrounding medium. Radio polarized emission is a very sensitive tracer of such interactions. In particular, regions of strong gas compression are often seen as polarized radio ridges, which mark regions of an enhanced magnetic field. Such enhancements can be however produced either by ram pressure or tidal effects. We present X-ray observations of a perturbed Virgo Cluster galaxy NGC 4569 and show that the analysis of the hot gas distribution and its spectral analysis in the regions where polarized radio ridges are seen, can help to distinguish between the two above scenarios.

The origin of the far-infrared emission from the nearby radio galaxy M87 remains a matter of debate. Some studies find evidence of a far-infrared excess due to thermal dust emission, whereas others propose that the far-infrared emission can be explained by synchrotron emission without the need for an additional dust emission component. We observed M87 with PACS and SPIRE as part of the Herschel Virgo Cluster Survey (HeViCS). We compare the new Herschel data with a synchrotron model based on infrared, submm and radio data to investigate the origin of the far-infrared emission. We find that both the integrated SED and the Herschel surface brightness maps are adequately explained by synchrotron emission. At odds with previous claims, we find no evidence of a diffuse dust component in M87., 4 pages, 2 figures, proceedings IAU Symposium 275 (Jets at all scales)

We present infrared colours (in the 25-500 mic spectral range) and UV to radio continuum spectral energy distributions of a sample of 51 nearby galaxies observed with SPIRE on Herschel. The observed sample includes all morphological classes, from quiescent ellipticals to active starbursts. Active galaxies have warmer colour temperatures than normal spirals. In ellipticals hosting a radio galaxy, the far-infrared (FIR) emission is dominated bynthe synchrotron nuclear emission. The colour temperature of the cold dust is higher in quiescent E-S0a than in star-forming systems probably because of the different nature of their dust heating sources (evolved stellar populations, X-ray, fast electrons) and dust grain properties. In contrast to the colour temperature of the warm dust, the f350/f500 index sensitive to the cold dust decreases with star formation and increases with metallicity, suggesting an overabundance of cold dust or an emissivity parameter beta, Accepted for publication on A&A, Herschel special issue

We present the dust properties of a small sample of Virgo cluster dwarf galaxies drawn from the science demonstration phase data set of the Herschel Virgo Cluster Survey. These galaxies have low metallicities (7.8 < 12 + log(O/H) < 8.3) and star-formation rates < 10^{-1} M_{sun}/yr. We measure the spectral energy distribution (SED) from 100 to 500 um and derive dust temperatures and dust masses. The SEDs are fitted by a cool component of temperature T < 20 K, implying dust masses around 10^{5} M_{sun} and dust-to-gas ratios D within the range 10^{-3}-10^{-2}. The completion of the full survey will yield a larger set of galaxies, which will provide more stringent constraints on the dust content of star-forming dwarf galaxies., Letter accepted for publication in A&A (Herschel special issue)

One‐dimensional decompositions oflight profiles of galaxies as introduced by Kormendy, where both bulge and disk profiles are fitted by a Sersic law, are applied to published data. Free parameters of the model are the central brightness, the scale length and the exponential‐power number. Thus the radial profile of a galaxy is specified by a superposition of a concave bulge profile and a convex disk profile. Decompositions of numerous profiles of nearby galaxies show a correlation between the Hubble type and bulge or disk exponential numbers. We confirm that with the increase of the morphologic type code of the luminous galaxies (when the mass of the galaxy decreases on average) the profile of the bulge tends to deviate from the de Vaucouleurs “1/4 law,” becoming less concave and more compact. We find at the same time that the radial profile of the disk becomes less convex and tends to be more close to a Freeman’s “exponential law.” The bulge‐to disk ratio, however, decreases also along the Hubble sequence. This fact raises the question which process leads to the changes in the shapes of the profiles of the bulge and disk, and relates it with the absolute mass or the bulge‐to‐disk ratio.

We present HST photometry of the LSB galaxy UGC 5889 and derive its recent star formation history. In the last 200 Myr the star formation proceeded in modest bursts at a rate of the order of e-2 to e-3 solar masses masses per year, with periods of extremely low SFR or even quiescence. The rate derived from the present study for the last 20 Myr is in agreement with the Halpha emission from the galaxy. The presence of a consistent population older than 200 Myr is suggested by the data. However, observational errors and completeness correction prevent any firm conclusion on the oldest age. The total mass of stars is of the order of 5.5e7 solas masses. Even if the recent episodes of star formation have heated the gas and carved a hole in the disk, blow-away of the gas is unlikely to occur., 11 pages, 13 figures, accepted for publication in A&A

Using the public data releases of the Sloan Digital Sky Survey (SDSS), we investigated the galaxy density around LSBs in comparison to High Surface Brightness (HSB) galaxies. We performed a number counting analysis in three dimensions within spheres of several radii on a sample of HSBs and LSBs with well measured SDSS redshifts. On scales between 2 and 5 Mpc our results show significantly lower galaxy densities in the vicinity of LSBs compared to HSBs. At larger scales than 5 Mpc, LSBs and HSBs share the same clustering properties but on scales below 2 Mpc the galaxy densities in the neighbourhood of LSBs lie systematically (but only with a slight significance) below that of HSBs. In the pie slice diagrams LSBs favour the outer rims of the filaments of the Large Scale Structure and some LSBs are even found in voids. These results give strong evidence to a formation and evolution scenario where LSBs were formed in low density environments. Hence, the lack of tidal interactions with companions must have cau...

In this work we investigate the surroundings of LBVs in M33 using images from the NOAO Local Group Survey. PSF photometry has been performed in all filters and color‐magnitude and color‐color diagrams were produced for the full data set. We present a closer look on the known LBVs in M33 which are Var B, Var C, Var 2 and Var 83. Presented is an analysis of their stellar and gaseous environment in order to examine the possible connection to nearby associations. This is tried among other things by estimating the distance the star could have travelled since its formation. The motivaton for this is to investigate whether massive stars are built in associations with other maybe also massive stars or if they form as single stars.

Using the Early Data Release of the Sloan Digital Sky Survey (SDSS) we investigated the clustering properties of Low Surface Brightness (LSB) galaxies in comparison to normal, High Surface Brightness (HSB) galaxies. We selected LSB galaxies and HSB galaxies with well measured redshifts from the SDSS data base and performed three-dimensional neighbour counting analysis within spheres of radii between 0.8 Mpc and 8.0 Mpc. As a second analysis method we used an N-th neighbour analysis with N varying from one to ten galaxies. Our results show significant differences between the galaxy densities of LSB galaxies and HSB galaxies on scales from 2 to 5 Mpc. At scales larger than 5 Mpc LSB and HSB galaxies share the same clustering properties. In the pie-slice diagrams the LSB galaxies appear to favour the inner rims of filaments as defined by the HSB galaxies, with a couple of LSB galaxies even being located inside the voids. Our results support the idea of gas-rich LSB galaxies forming and developing in low density regions without many galaxy interactions and just now reaching the filaments of the large scale structure., 4 pages, 5 figures, Astronomy & Astrophysics Letters in press

NGC 4449 is an irregular galaxy with a moderately high star formation activity. The massive stars in NGC 4449 have given rise to many bright HII regions, superbubbles, supergiant shells, and "chimney-like" radial filaments. ROSAT X-ray observations of NGC 4449 have revealed four point-like sources and a wide-spread diffuse emission. The spectral properties of the diffuse component suggest that the emission originates from hot interstellar gas. We have compared deep ground-based H-alpha images with the X-ray images of NGC 4449 to determine the relationship between the hot (10^6 K) and the warm (10^4 K) components of the interstellar gas. We have also used an archival Hubble Space Telescope WFPC2 image of NGC 4449 taken through the F606W filter to examine the massive stellar content of the X-ray-emission regions. We find that hot interstellar gas exists in (1) active star forming regions, including the giant H II region CM 16, (2) probable outflows from star forming regions, and (3) the supergiant shell SGS2. The X-ray data have been used to derive the rms electron density, mass, and thermal energy of the hot interior of SGS2. Finally we discuss the origin of SGS2 and implications of the detection of diffuse X-rays in irregular galaxies., 14 pages, LaTeX (aas2pp4.sty), 14 jpg figures, Astronomical Journal, in press (May 1997 issue)

Supergiant shells are the largest interstellar structures in galaxies. They are outlined by long H II filaments enclosing an inner space containing very little warm or cold gas. In the LMC, two supergiant shells have been detected in X-rays indicating the existence of hot gas: LMC2 (Wang & Helfand 1992) and LMC 4 (Bomans et al. 1994). It is not yet clear whether the hot gas in a galactic halo is supplied by such supergiant shells.

Shapley Constellation HI in the north of the LMC is one of the largest associations in the LMC. It is surrounded by a ring of H II regions and diffuse H II filaments called Supergiant Shell LMC 4 (Goudis & Meaburn 1978). LMC 4 is suspected to be a site of large scale propagation of star formation (Dopita et al. 1985), but recent studies (Reid et al. 1987; Vallenari et al. 1993) show that the situation is far from simple.

CCD photometry of 4 fields in Region C (de Boer et al., 1989 and 1991) at the NW side of the LMC and of 10 fields in Region E at the NW edge of supershell LMC4 in the NE shows that the stellar population comes from a wide range of star formation epochs. We have reduced the data with DAOPHOT and we can thus produce colour-magnitude diagrams (CMDs) with error indications and with proper information on completeness of the data. Field stars are subtracted. The CMDs are used to derive ages and mass functions.

In order to investigate dynamics, three-dimensional structure and physical conditions of the interstellar gas in the giant superbubble LMC4 we have analysed IUE high dispersion spectra of seven hot stars in this part of the LMC in comparison with 21cm emission data.

We use the Science Demonstration Phase data of the Herschel Virgo Cluster Survey to search for dust emission of early-type dwarf galaxies in the central regions of the Virgo Cluster as an alternative way of identifying the interstellar medium.We present the first possible far-infrared detection of cluster early-type dwarf galaxies: VCC781 and VCC951 are detected at the 10 sigma level in the SPIRE 250 micron image. Both detected galaxies have dust masses of the order of 10^5 Msun and average dust temperatures ~20K. The detection rate (less than 1%) is quite high compared to the 1.7% detection rate for Hi emission, considering that dwarfs in the central regions are more Hi deficient. We conclude that the removal of interstellar dust from dwarf galaxies resulting from ram pressure stripping, harassment, or tidal effects must be as efficient as the removal of interstellar gas., Letter accepted for publication in A&A (Herschel special issue)

BVR photometry of stellar fields in the NW region of supergiant shell LMC4 has been performed. We present preliminary results on the age of the stellar populations in this part of the LMC.

We present first results of our study of the interplay between the 106 K, 104 K, 102 K gas phases in the supergiant shell LMC 4.

Our recently obtained HST WFPC2 images of N63A reveal shocked cloudlets in the SNR interior. The study of N63A helps us understand the structure and evolution of SNRs in a cloudy medium.

In a kinematic study of LMC \hii\ regions, we serendipitously found a fast-expanding (velocity offsets up to ~200 \kms) shell in the northern lobe of the luminous \hii\ region N159. The expansion pattern and the \sii/\ha\ ratio of the shell are consistent with those seen in supernova remnants (SNRs). Confirmation of this SNR candidate in radio and X-ray wavelengths has been hampered by thermal emission of the luminous \hii\ region N159 itself and scattered X-rays from the nearby luminous source LMC X-1. Recent {ROSAT} observations finally resolved N159 from LMC X-1, thus confirming the identification of this as a newly identified SNR, which we designate as SNR 0540-697.