TY - JOUR A1 - Weilbacher, Peter Michael A1 - Monreal-Ibero, Ana A1 - Verhamme, Anne A1 - Sandin, Christer A1 - Steinmetz, Matthias A1 - Kollatschny, Wolfram A1 - Krajnovic, Davor A1 - Kamann, Sebastian A1 - Roth, Martin M. A1 - Erroz-Ferrer, Santiago A1 - Marino, Raffaella Anna A1 - Maseda, Michael V. A1 - Wendt, Martin A1 - Bacon, Roland A1 - Dreizler, Stefan A1 - Richard, Johan A1 - Wisotzki, Lutz T1 - Lyman-continuum leakage as dominant source of diffuse ionized gas in the Antennae galaxy JF - Astronomy and astrophysics : an international weekly journal N2 - The Antennae galaxy (NGC 4038/39) is the closest major interacting galaxy system and is therefore often studied as a merger prototype. We present the first comprehensive integral field spectroscopic dataset of this system, observed with the MUSE instrument at the ESO VLT. We cover the two regions in this system which exhibit recent star formation: the central galaxy interaction and a region near the tip of the southern tidal tail. In these fields, we detect H II regions and diffuse ionized gas to unprecedented depth. About 15% of the ionized gas was undetected by previous observing campaigns. This newly detected faint ionized gas is visible everywhere around the central merger, and shows filamentary structure. We estimate diffuse gas fractions of about 60% in the central field and 10% in the southern region. We are able to show that the southern region contains a significantly different population of H II regions, showing fainter luminosities. By comparing H II region luminosities with the HST catalog of young star clusters in the central field, we estimate that there is enough Lyman-continuum leakage in the merger to explain the amount of diffuse ionized gas that we detect. We compare the Lyman-continuum escape fraction of each H II region against emission line ratios that are sensitive to the ionization parameter. While we find no systematic trend between these properties, the most extreme line ratios seem to be strong indicators of density bounded ionization. Extrapolating the Lyman-continuum escape fractions to the southern region, we conclude that simply from the comparison of the young stellar populations to the ionized gas there is no need to invoke other ionization mechanisms than Lyman-continuum leaking H II regions for the diffuse ionized gas in the Antennae. KW - galaxies: interactions KW - galaxies: individual: NGC 4038, NGC 4039 KW - galaxies: ISM KW - ISM: structure KW - H II regions Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201731669 SN - 1432-0746 VL - 611 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Husser, Tim-Oliver A1 - Kamann, Sebastian A1 - Dreizler, Stefan A1 - Wendt, Martin A1 - Wulff, Nina A1 - Bacon, Roland A1 - Wisotzki, Lutz A1 - Brinchmann, Jarle A1 - Weilbacher, Peter Michael A1 - Roth, Martin M. A1 - Monreal-Ibero, Ana T1 - MUSE crowded field 3D spectroscopy of over 12 000 stars in the globular cluster NGC 6397 I. The first comprehensive HRD of a globular cluster JF - Nucleic acids research N2 - Aims. We demonstrate the high multiplex advantage of crowded field 3D spectroscopy with the new integral field spectrograph MUSE by means of a spectroscopic analysis of more than 12 000 individual stars in the globular cluster NGC 6397. Methods. The stars are deblended with a point spread function fitting technique, using a photometric reference catalogue from HST as prior, including relative positions and brightnesses. This catalogue is also used for a first analysis of the extracted spectra, followed by an automatic in-depth analysis via a full-spectrum fitting method based on a large grid of PHOENIX spectra. Results. We analysed the largest sample so far available for a single globular cluster of 18 932 spectra from 12 307 stars in NGC 6397. We derived a mean radial velocity of v(rad) = 17.84 +/- 0.07 km s(-1) and a mean metallicity of [Fe/H] = -2.120 +/- 0.002, with the latter seemingly varying with temperature for stars on the red giant branch (RGB). We determine Teff and [Fe/H] from the spectra, and log g from HST photometry. This is the first very comprehensive Hertzsprung-Russell diagram (HRD) for a globular cluster based on the analysis of several thousands of stellar spectra, ranging from the main sequence to the tip of the RGB. Furthermore, two interesting objects were identified; one is a post-AGB star and the other is a possible millisecond-pulsar companion. KW - methods: data analysis KW - techniques: imaging spectroscopy KW - planets and satellites: fundamental parameters KW - stars: atmospheres KW - pulsars: general KW - globular clusters: individual: NGC 6397 Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201526949 SN - 1432-0746 VL - 588 PB - EDP Sciences CY - Les Ulis ER -