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  • 1.
    Cumming, Robert J.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Marquart, Thomas
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, Department of Astronomy.
    Bergvall, Nils
    Adamo, Angela
    Stockholm University, Faculty of Science, Department of Astronomy.
    Stellar kinematics in blue compact galaxies2009Other (Other (popular science, discussion, etc.))
    Abstract [en]

    In a programme of observations of local luminous blue compact galaxies (BCGs), we are investigating kinematics by using tracers of both stars and ionized gas. Here we summarise our program and present new data on the local Lyman break galaxy analogue Haro 11. From spatially-resolved spectroscopy around the near-infrared Ca II triplet, we find that its stars and ionized gas have similar velocity fields. Our programme so far indicates however that emission line velocities can differ locally by a few tens of km/s from the Ca II values. Comparing our data to simple stellar population models, we assess which stellar population the Ca II triplet traces and its potential beyond the local universe.

  • 2.
    Cumming, Robert James
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Marquart, Thomas
    Masegosa, Josefa
    Bergvall, Nils
    Amram, Philippe
    Stellar dynamics of blue compact galaxies.: II. Further indications of a merger in ESO 338-IG042008In: Astronomy & Astrophysics, Vol. 479, no 3Article in journal (Refereed)
    Abstract [en]

    Context: Luminous blue compact galaxies, common at z ~ 1 but now relatively rare, show disturbed kinematics in emission lines. Aims: As part of a programme to understand their formation and evolution, we have investigated the stellar dynamics of a number of nearby objects in this class. Methods: We obtained long-slit spectra with VLT/FORS2 in the spectral region covering the near-infrared calcium triplet. In this paper we focus on the well-known luminous blue compact galaxy ESO 338-IG04 (Tololo 1924-416). A previous investigation, using Fabry-Perot interferometry, showed that this galaxy has a chaotic Hα velocity field, indicating that either the galaxy is not in dynamical equilibrium or that Hα does not trace the gravitational potential due to feedback from star formation. Results: Along the apparent major axis, the stellar and ionised gas velocities for the most part follow each other. The chaotic velocity field must therefore be a sign that the young stellar population in ESO 338-IG04 is not in dynamical equilibrium. The most likely explanation, which is also supported by its morphology, is that the galaxy has experienced a merger and that this has triggered the current starburst. Summarising the results of our programme so far, we note that emission-line velocity fields are not always reliable tracers of stellar motions, and go on to assess the implications for kinematic studies of similar galaxies at intermediate redshift.

  • 3.
    Cumming, Robert
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Marquart, Thomas
    Fathi, Kambiz
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergvall, Nils
    Adamo, Angela
    Stockholm University, Faculty of Science, Department of Astronomy.
    Stellar kinematics in blue compact galaxies2009Report (Other academic)
    Abstract [en]

    In a programme of observations of local luminous blue compact galaxies (BCGs), we are investigating kinematics by using tracers of both stars and ionized gas. Here we summarise our program and present new data on the local Lyman break galaxy analogue Haro 11. From spatially-resolved spectroscopy around the near-infrared Ca II triplet, we find that its stars and ionized gas have similar velocity fields. Our programme so far indicates however that emission line velocities can differ locally by a few tens of km/s from the Ca II values. Comparing our data to simple stellar population models, we assess which stellar population the Ca II triplet traces and its potential beyond the local universe.

  • 4.
    Micheva, Genoveva
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bergvall, Nils
    Zackrisson, Erik
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Masegosa, Josefa
    Marquez, Isabel
    Marquart, Thomas
    Stockholm University, Faculty of Science, Department of Astronomy. Uppsala University.
    Durret, Florence
    Deep multiband surface photometry on a sample of 24 blue compact galaxies - I2013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 431, no 1, p. 102-144Article in journal (Refereed)
    Abstract [en]

    We present deep optical and near-infrared (NIR) UBVRIHKs imaging data for 24 blue compact galaxies (BCGs). The individual exposure times are on average similar to 40 min in the optical (B) and similar to 90 min in the NIR, but on occasion up to similar to 5 h for a single target and filter, observed with 2.5, 3.5, 8.2-m telescopes. The sample contains luminous dwarf and intermediate-mass BCGs which are predominantly metal poor, although a few have near-solar metallicities. We have analysed isophotal and elliptical integration surface brightness and colour profiles, extremely deep (mu(B) less than or similar to 29 mag arcsec(-2)) contour maps and RGB images for each galaxy in the sample, and provide a morphological classification where such is missing. Separating the burst from the underlying host we find that regardless of the total luminosity the host galaxy has the properties of a low surface brightness (LSB) dwarf with M-B greater than or similar to -18. For a number of galaxies we discover a distinct LSB component dominant around and beyond the Holmberg radius. For the specific case of ESO 400-43A&B we detect an optical bridge between the two companion galaxies at the mu(V) similar to 28th mag arcsec(-2) isophotal level. Synthetic disc tests are performed to verify that we can trace such faint components with negligible errors down to mu(B) = 28 and mu(K) = 23 mag arcsec(-2). By examining the structural parameters (central surface brightness mu(0) and scalelength h(r)) derived from two radial ranges typically assumed to be dominated by the underlying host galaxy, we demonstrate the importance of sampling the host well away from the effects of the burst. We find that mu(0) and h(r) of the BCGs host deviate from those of dwarf ellipticals (dEs) and dwarf irregulars (dI) solely due to a strong burst contribution to the surface brightness profile almost down to the Holmberg radius. Structural parameters obtained from a fainter region, mu(B) = 26-28 mag arcsec(-2), are consistent with those of true LSB galaxies for the starbursting BCGs in our sample, and with dEs and dIs for the BCGs with less vigorous star formation.

  • 5.
    Micheva, Genoveva
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zackrisson, Erik
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bergvall, N.
    Marquart, Thomas
    Stockholm University, Faculty of Science, Department of Astronomy.
    Masegosa, J.
    Marquez, I.
    Cumming, R. J.
    Durret, F.
    Deep multiband surface photometry on a sample of 24 blue compact galaxies II. A volume-limited sample of 21 emission line galaxies2013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 556, p. A10-Article in journal (Refereed)
    Abstract [en]

    Aims. We present deep surface photometry of a volume-limited sample of 21 UM emission line galaxies in broadband optical UBVRI and near infrared (NIR) HKs filters. The sample comprises 19 blue compact galaxies (BCGs) and two spirals. Methods. We separated the burst and host populations for each galaxy and compared them to stellar evolutionary models with and without nebular emission contribution. We measured and analyzed the A(180) asymmetry in all filters, the concentration index C, the scale length, and the central surface brightness of the host galaxy. Results. A shift in the average A180 asymmetry is detected from optical to NIR. This shift seems correlated with the morphological class of the BCGs. Using the color-asymmetry relation, we identify five BCGs in the sample as mergers, which is confirmed by their morphological class. Though clearly separated from normal galaxies in the concentration-asymmetry parameter space, we find that it is not possible to distinguish luminous starbursting BCGs from the merely star forming low luminosity BCGs.

  • 6.
    Östlin, Göran
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hayes, Matthew
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Duval, Florent
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sandberg, Andreas
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rivera-Thorsen, Thöger
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Marquart, Thomas
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Uppsala University, Sweden.
    Orlitova, Ivana
    Adamo, Angela
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Melinder, Jens
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Guaita, Lucia
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Atek, Hakim
    Cannon, John M.
    Gruyters, Pieter
    Herenz, Edmund Christian
    Kunth, Daniel
    Laursen, Peter
    Mas-Hesse, J. Miguel
    Micheva, Genoveva
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Subaru Telescope, National Astronomical Observatory of Japan, USA.
    Oti-Floranes, Hector
    Pardy, Stephen A.
    Roth, Martin M.
    Schaerer, Daniel
    Verhamme, Anne
    THE Ly alpha REFERENCE SAMPLE. I. SURVEY OUTLINE AND FIRST RESULTS FOR MARKARIAN 2592014In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 797, no 1, article id 11Article in journal (Refereed)
    Abstract [en]

    The Ly alpha Reference Sample (LARS) is a substantial program with the Hubble Space Telescope (HST) that provides a sample of local universe laboratory galaxies in which to study the detailed astrophysics of the visibility and strength of the Ly alpha line of neutral hydrogen. Ly alpha is the dominant spectral line in use for characterizing high-redshift (z) galaxies. This paper presents an overview of the survey, its selection function, and HST imaging observations. The sample was selected from the combined GALEX+Sloan Digital Sky Survey catalog at z = 0.028-0.19, in order to allow Ly alpha to be captured with combinations of long-pass filters in the Solar Blind Channel (SBC) of the Advanced Camera for Surveys (ACS) onboard HST. In addition, LARS utilizes H alpha and H beta narrowband and u, b, i broadband imaging with ACS and the Wide Field Camera 3 (WFC3). In order to study galaxies in which large numbers of Ly alpha photons are produced (whether or not they escape), we demanded an H alpha equivalent width W(H alpha) >= 100 angstrom. The final sample of 14 galaxies covers far-UV (FUV, lambda similar to 1500 angstrom) luminosities that overlap with those of high-z Ly alpha emitters (LAEs) and Lyman break galaxies (LBGs), making LARS a valid comparison sample. We present the reduction steps used to obtain the Ly alpha images, including our LARS eXtraction software (LaXs), which utilizes pixel-by-pixel spectral synthesis fitting of the energy distribution to determine and subtract the continuum at Ly alpha. We demonstrate that the use of SBC long-pass-filter combinations increase the signal-to-noise ratio by an order of magnitude compared to the nominal Ly alpha filter available in SBC. To exemplify the science potential of LARS, we also present some first results for a single galaxy, Mrk 259 (LARS #1). This irregular galaxy shows bright and extended (indicative of resonance scattering) but strongly asymmetric Ly alpha emission. Spectroscopy from the Cosmic Origins Spectrograph on board HST centered on the brightest UV knot shows a moderate outflow in the neutral interstellar medium (probed by low ionization stage absorption features) and Ly alpha emission with an asymmetric profile. Radiative transfer modeling is able to reproduce the essential features of the Ly alpha line profile and confirms the presence of an outflow. From the integrated photometry we measure an Ly alpha luminosity of L-Ly alpha= 1.3x10(42) erg s(-1) an equivalent width W(Ly alpha) = 45 angstrom and an FUV absolute magnitude M-FUV = -19.2 (AB). Mrk 259 would hence be detectable in high-z Ly alpha and LBG surveys. The total Ly alpha escape fraction is 12%. This number is higher than the low-z average, but similar to that at z > 4, demonstrating that LARS provides a valid comparison sample for high-z galaxy studies.

1 - 6 of 6
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