The young researchers of Abastumani Astrophysical Observatory, Zurab Vashalomidze and Ia Kochiashvili were awarded the Blaise Pascal Young Researcher Prize of Ilia State University (about Pascal prize, see the link on Iliauni website)
Zurab Vashalomidze for his scientific article : “Formation and evolution of coronal rain observed by SDO/AIA on February 22, 2012“
Ia Kochiashvili for her scientific article : “Emission-line-selected galaxies at z = 0.6-2 in GOODS South: Stellar masses, SFRs, and large-scale structure“
Formation and evolution of coronal rain observed by SDO/AIA on February 22, 2012, abstract:
Context. The formation and dynamics of coronal rain are currently not fully understood. Coronal rain is the fall of cool and dense blobs formed by thermal instability in the solar corona towards the solar surface with acceleration smaller than gravitational free fall.
Aims: We aim to study the observational evidence of the formation of coronal rain and to trace the detailed dynamics of individual blobs.
Methods: We used time series of the 171 Å and 304 Å spectral lines obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) above active region AR 11420 on February 22, 2012.
Results: Observations show that a coronal loop disappeared in the 171 Å channel and appeared in the 304 Å line more than one hour later, which indicates a rapid cooling of the coronal loop from 1 MK to 0.05 MK. An energy estimation shows that the radiation is higher than the heat input, which indicates so-called catastrophic cooling. The cooling was accompanied by the formation of coronal rain in the form of falling cold plasma. We studied two different sequences of falling blobs. The first sequence includes three different blobs. The mean velocities of the blobs were estimated to be 50 km s-1, 60 km s-1 and 40 km s-1. A polynomial fit shows the different values of the acceleration for different blobs, which are lower than free-fall in the solar corona. The first and second blob move along the same path, but with and without acceleration, respectively. We performed simple numerical simulations for two consecutive blobs, which show that the second blob moves in a medium that is modified by the passage of the first blob. Therefore, the second blob has a relatively high speed and no acceleration, as is shown by observations. The second sequence includes two different blobs with mean velocities of 100 km s-1 and 90 km s-1, respectively.
Conclusions: The formation of coronal rain blobs is connected with the process of catastrophic cooling. The different acceleration of different coronal rain blobs might be due to the different values in the density ratio of blob to corona. All blobs leave trails, which might be a result of continuous cooling in their tails.
Emission-line-selected galaxies at z = 0.6-2 in GOODS South: Stellar masses, SFRs, and large-scale structure, abstract:
We have obtained deep NIR narrow and broad (J and Y) band imaging data of the GOODS-South field. The narrow band filter is centered at 1060 nm corresponding to redshifts z = 0.62,1.15,1.85 for the strong emission lines Hα, [Oiii]/Hβ and [Oii], respectively. From those data we extract a well defined sample (M(AB) = 24.8 in the narrow band) of objects with large emission line equivalent widths in the narrow band. Via SED fits to published broad band data we identify which of the three lines we have detected and assign redshifts accordingly. This results in a well defined, strong emission line selected sample of galaxies down to lower masses than can easily be obtained with only continuum flux limited selection techniques. We compare the (SED fitting-derived) main sequence of star-formation (MS) of our sample to previous works and find that it has a steeper slope than that of samples of more massive galaxies. We conclude that the MS steepens at lower (below M⋆ = 109.4M⊙) galaxy masses. We also show that the SFR at any redshift is higher in our sample. We attribute this to the targeted selection of galaxies with large emission line equivalent widths, and conclude that our sample forms the upper boundary of the MS. We briefly investigate and outline how samples with accurate redshifts down to those low stellar masses open a new window to study the formation of large scale structure in the early universe. In particular we report on the detection of a young galaxy cluster at z = 1.85 which features a central massive galaxy which is the candidate of an early stage cD galaxy, and we identify a likely filament mapped out by [Oiii] and Hβ emitting galaxies at z = 1.15.