Hintze Centre for Astrophysical Surveys

Abstract:

<jats:title>ABSTRACT</jats:title> <jats:p>Galaxy clusters have long been theorized to quench the star formation of their members. This study uses integral-field unit observations from the K-band MultiObject Spectrograph (KMOS) – Cluster Lensing And Supernova survey with Hubble (CLASH) survey (K-CLASH) to search for evidence of quenching in massive galaxy clusters at redshifts 0.3 &amp;lt; z &amp;lt; 0.6. We first construct mass-matched samples of exclusively star-forming cluster and field galaxies, then investigate the spatial extent of their H α emission and study their interstellar medium conditions using emission line ratios. The average ratio of H α half-light radius to optical half-light radius ($r_{\mathrm{e}, {\rm {H}\,\alpha }}/r_{\mathrm{e}, R_{\mathrm{c} } }$) for all galaxies is 1.14 ± 0.06, showing that star formation is taking place throughout stellar discs at these redshifts. However, on average, cluster galaxies have a smaller $r_{\mathrm{e}, {\rm {H}\alpha }}/r_{\mathrm{e}, R_{\mathrm{c} } }$ ratio than field galaxies: 〈$r_{\mathrm{e}, {\rm {H}\alpha }}/r_{\mathrm{e}, R_{\mathrm{c} } }$〉 = 0.96 ± 0.09 compared to 1.22 ± 0.08 (smaller at a 98 per cent credibility level). These values are uncorrected for the wavelength difference between H α emission and Rc-band stellar light but implementing such a correction only reinforces our results. We also show that whilst the cluster and field samples follow indistinguishable mass–metallicity (MZ) relations, the residuals around the MZ relation of cluster members correlate with cluster-centric distance; galaxies residing closer to the cluster centre tend to have enhanced metallicities (significant at the 2.6σ level). Finally, in contrast to previous studies, we find no significant differences in electron number density between the cluster and field galaxies. We use simple chemical evolution models to conclude that the effects of disc strangulation and ram-pressure stripping can quantitatively explain our observations.</jats:p>

Abstract:

This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).

Abstract:

Core-collapse supernovae (CCSNe) are the bright explosions of massive stars. During the explosion heavy elements are produced by nuclear burning. One of these products is 56Ni that radioactively decays into 56Co. The explosion energy and the produced 56Ni and its product 56Co are what powers the light curves of classical supernovae (SNe). Stripped envelope (SE) SNe have lost their hydrogen (H) and in some cases, helium (He) envelopes through mass loss at some point in their lives. These SE SNe are known to produce SNe of types IIb (weak H), Ib (He-rich), Ic (He-poor), and Ic-BL (He-poor broad lines). Type IIn SNe, on the other hand, are SNe that interact with circumstellar medium (CSM) around the progenitor. The CSM is thought to be caused by the progenitor’s mass loss. The mechanism of the mass loss for these can happen in a variety of ways. All stars have mass loss through stellar winds, but in some cases, it is not enough to produce interaction that would produce a type IIn. The mass loss can also happen because of pair instability pulsations, eruptions, or binary effects. The mass loss can be studied by analysing the observational properties of a SN and understanding the mass loss might shed light on what kind of progenitor produced the SN. In this thesis, photometric and spectroscopic data of SN 2017dio are analysed. The photometric data are used to study the explosion epoch, light curves, and color curves of SN 2017dio and it is compared with four other SNe. The spectroscopic data are used to verify the classification of SN 2017dio, to study the spectral evolution, and to discuss the possible CSM properties and progenitor scenario. The findings indicate that SN 2017dio is a SN of type Ic-BL interacting with H-rich CSM. Both spectroscopic and photometric analysis support the theory of the CSM not being close to the explosion site and the calculated mass loss rate 0.04M⊙/year indicates that the progenitor must have experienced massive mass loss periods in the decade before its explosion