| 1. |
- Milisavljevic, Dan, et al.
(författare)
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MULTI-WAVELENGTH OBSERVATIONS OF SUPERNOVA 2011ei : TIME-DEPENDENT CLASSIFICATION OF TYPE IIb AND Ib SUPERNOVAE AND IMPLICATIONS FOR THEIR PROGENITORS
- 2013
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 767:1, s. 71-
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Tidskriftsartikel (refereegranskat)abstract
- We present X-ray, UV/optical, and radio observations of the stripped-envelope, core-collapse supernova (SN) 2011ei, one of the least luminous SNe IIb or Ib observed to date. Our observations begin with a discovery within similar to 1 day of explosion and span several months afterward. Early optical spectra exhibit broad, Type II-like hydrogen Balmer profiles that subside rapidly and are replaced by Type Ib-like He-rich features on a timescale of one week. High-cadence monitoring of this transition suggests absorption attributable to a high-velocity (greater than or similar to 12,000 km s(-1)) H-rich shell, which is likely present in many Type Ib events. Radio observations imply a shock velocity of v approximate to 0.13 c and a progenitor star average mass-loss rate of (M) over dot approximate to 1.4 x 10(-5) M-circle dot yr(-1) (assuming wind velocity v(w) = 10(3) km s(-1)). This is consistent with independent constraints from deep X-ray observations with Swift-XRT and Chandra. Overall, the multi-wavelength properties of SN 2011ei are consistent with the explosion of a lower-mass (3-4 M-circle dot), compact (R-* less than or similar to 1 x 10(11) cm), He-core star. The star retained a thin hydrogen envelope at the time of explosion, and was embedded in an inhomogeneous circumstellar wind suggestive of modest episodic mass loss. We conclude that SN 2011ei's rapid spectral metamorphosis is indicative of time-dependent classifications that bias estimates of the relative explosion rates for Type IIb and Ib objects, and that important information about a progenitor star's evolutionary state and mass loss immediately prior to SN explosion can be inferred from timely multi-wavelength observations.
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| 2. |
- Vaisanen, Petri, et al.
(författare)
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Adaptive optics imaging and optical spectroscopy of a multiple merger in a luminous infrared galaxy
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We present near-infrared (NIR) adaptive optics imaging obtained with VLT/NACO and optical spectroscopy from the Southern African Large Telescope (SALT) of a luminous infrared galaxy (LIRG) IRAS 19115-2124. These data are combined with archival HST imaging and Spitzer imaging and spectroscopy, allowing us to study this disturbed interacting/merging galaxy, dubbed the Bird, in extraordinary detail. In particular, the data reveal a triple system where the LIRG phenomenon is dominated by the smallest of the components.One nucleus is a regular barred spiral with significant rotation, while another is highly disturbed with a surface brightness distribution intermediate to that of disk and bulge systems, and hints of remaining arm/bar structure. We derive dynamical masses in the range 3-7x10^10 M_solar for both. The third component appears to be a 1-2x10^10 M_solar mass irregular galaxy. The total system exhibits HII galaxy-like optical line ratios and strengths, and no evidence for AGN activity is found from optical or mid-infrared data. The star formation rate is estimated to be 190 M_solar/yr. We search for SNe, super star clusters, and detect 100-300 km/s outflowing gas from the Bird. Overall, the Bird shows kinematic, dynamical, and emission line properties typical for cool ultra luminous IR galaxies. However, the interesting features setting it apart for future studies are its triple merger nature, and the location of its star formation peak - the strongest star formation does not come from the two major K-band nuclei, but from the third irregular component. Aided by simulations, we discuss scenarios where the irregular component is on its first high-speed encounter with the more massive components.
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| 3. |
- Vaisanen, Petri, et al.
(författare)
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Super star clusters and Supernovae in interacting LIRGs unmasked by NIR adaptive optics
- 2010
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Ingår i: proceedings of 'Galaxies and their Masks' (Namibia, April 2010), published by Springer.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We report on an on-going near-IR adaptive optics survey targeting interacting luminous IR galaxies. High-spatial resolution NIR data are crucial to enable interpretation of kinematic, dynamical and star formation (SF) properties of these very dusty objects. Whole progenitor nuclei in the interactions can be missed if only optical HST imaging is used. Here we specifically present the latest results regarding core-collapse supernovae found within the highly extincted nuclear regions of these galaxies. Direct detection and study of such highly obscured CCSNe is crucial for revising the optically-derived SN rates used for providing an independent measurement of the SF history of the Universe. We also present thus-far the first NIR luminosity functions of super star cluster (SSC) candidates. The LFs can then be used to constrain the formation and evolution of SSCs via constraints based on initial mass functions and cluster disruption models.
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