0 Assigned ID: 579 ----- Attempting Submission 1 (Fri Apr 07 15:39:54 GMT 2017) ----- See email by wrh@astro.physik.uni-potsdam.de from today (2018 Aug 7) -1755716063 ----- Attempting Submission 1 (Fri Jul 07 15:05:34 GMT 2017) ----- HST Phase II Proposal 15112 (ngc346-phase2.apt) successfully submitted. Receipt: # 15112-1 ----- Attempting Submission 2 (Tue Aug 07 14:27:46 GMT 2018) ----- The low-metallicity starburst NGC346: massive-star population and feedback The Small Magellanic Cloud (SMC) is ideal to study young, massive stars at low metallicity. The compact cluster NGC346 contains about half of all O-type stars in the entire SMC. The massive-star population of this cluster powers N66, the brightest and largest HII region in the SMC. We propose to use HST-STIS to slice NGC346 with 20 long-slit exposures, in order to obtain the UV spectra of most of the massive early-type stars of this cluster. Archival data of 13 exposures that cover already a minor part of this cluster will be included in our analyses. Our aim is to quantitatively analyze virtually the whole massive-star population of NGC346. We have already secured the optical spectra of all massive stars in the field with the integral-field spectrograph MUSE at the ESO-VLT. However, for the determination of the stellar-wind parameters, i.e. the mass-loss rates and the wind velocities, ultraviolet spectra are indispensable. Our advanced "Potsdam Wolf-Rayet (PoWR)" code will be used for modeling the stellar and wind spectra in the course of the analysis. Finally, we will obtain: (a) the fundamental stellar and wind parameters of all stars brighter than spectral type B2V in the field, which, e,g,, will constrain the initial mass function in this young low-metallicity starburst; (b) mass-loss rates of many more OB-type stars at SMC metallicity than hitherto known, allowing to better constrain their metallicity dependence; (c) the integrated feedback by ionizing radiation and stellar winds of the whole massive-star population of NGC346, which will be used as input to model the ecology of the giant HII region N66. These HST UV data will be of high legacy value. The observations shall map major parts of the young stellar cluster NGC346 in the SMC. We want to take STIS long-slit UV spectra arranged in mosaic of adjacent slit positions. The slit is 52" x 2", and the positions should overlap by 0.2" in dispersion direction. The aim is to extract as many as possible stellar spectra of the blue cluster stars. The fields are carefully chosen, taking into account that a minor part of the cluster has already been observed with a similar technique with STIS before (GO-8629, PI Bruhweiler), see Figure3 of the Phase I proposal. For the visual brightness that is requested in the "target" forms we have always given the UV-brightes star in the whole mosaic field (Cl* NGC346 W3, V=12.8mag), although this star is only covered by one of the slit postions. For the precise positioning of the slit exposures, we use first a reference star for target acquisition and peakup. Then, the slit is positiond with relative offsets using the "STIS PERP-TO-SLIT" pattern. In addition to the coordinate offsets, we apply an offset ot 3" in slit direction in order to account for the spectral offset of the MAMA detector described in Sect. 7.6 of the "STIS Instrument Handbook for Cycle 25" (Version 16.0). Our mosaic coverage requires a position angle of the slit of about 35deg. We specify here a tolerance of plus/minus 10deg in order to allow for larger windows of visibility. If this would still lead to scheduling problems, we could release this constraint further. In any case, we would ask to contact us when the orbits have been scheduled and the exact position angle of the slit is known, so that we could check and re-adjust the position offsets in order not to miss any interesting star. Following the special note for Cycle 25, we have structured our 5 orbits into visits of 3 + 2 orbits. If it would finally happen that the orbits can be scheduled back-to-back, the target acquision and peakup at the beginning of orbit 4 would not be necessary and the time can be distributed for the science exposures. In each orbit we have left 165s at the end unused, because we noticed that otherwise the visibility is strongly redued. Of course, finally all available time should be evenly distributed to extend the science exposures to the maximum possible. Stellar Populations Stellar Physics 6 false false true false false false false SUPPORTED STAR OF NO J2000 STELLAR CLUSTER OPEN CLUSTER J2000 abmag=12.8 in filter WFC3/UVIS/F225W STELLAR CLUSTER OPEN CLUSTER J2000 abmag>13.06 in filter WFC3/UVIS/F225W STELLAR CLUSTER OPEN CLUSTER J2000 abmag>13.06 in filter WFC3/UVIS/F225W STELLAR CLUSTER OPEN CLUSTER J2000 abmag>13.06 in filter WFC3/UVIS/F225W STELLAR CLUSTER OPEN CLUSTER J2000 abmag>13.06 in filter WFC3/UVIS/F225W STAR OF NO J2000 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/FUV-MAMA Spectroscopic No No G140L 1425 POS-TARG MOSAIC DITHER 1.8 STIS-ALONG-SLIT false false 4 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 1 false POS-TARG MOSAIC DITHER 1.8 STIS-ALONG-SLIT false false 3 0.0 POS-TARG STIS-PERP-TO-SLIT 90.0 2 false /tmp/OPVisit4439209985809653128.xml The scheduling data was generated by CASM 26.0. CASM was run in Phase II mode. 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