Ia型超新星中包含了典型的Ia型超新星和特殊的超新星，典型Ia型超新星是測量宇宙膨脹的可標準化燭光。而特殊的Ia型超新星中，91T-like超新星比起典型的Ia型超新星來得亮，也更容易在高紅移的宇宙中被發現，所以我們想找出並研究在高紅移的巡天計畫中所發現的91T-like超新星。我們的母樣本為約400顆來自Pan-STARRS1 Medium Deep Survey (PS1-MDS)的高紅移超新星，而我們使用了其光譜分類出16顆91T-like超新星，並進一步探討其特性。我們主要發現91T-like超新星的光度曲線下降率平均來說比起正常的Ia型超新星來得慢，這也與其較亮的光度一致，且其Hubble Residual傾向為負值。而91T-like超新星的顏色和其他類別的超新星相比並沒有明顯的差異，可能是受到星系裡塵埃的影響。再來是宿主星系的質量、恆星形成率和特定的恆星形成率，我們發現91T-like超新星的宿主星系質量和其他類別相比沒有明顯的差異，而91T-like超新星傾向出現在高恆星形成率和較高的特定恆星形成率的星系，較不會出現在很老或接近死亡的星系中。這些結果顯示高紅移的91T-like超新星與先前低紅移研究中的91T-like超新星有著一致的特性。

Type Ia supernovae (SNe Ia) can be classified into many sub-types, including normal SNe Ia and several peculiar types such as 91-like and 91bg-like SNe Ia. Normal SNe~Ia are widely used as standardized candles for measuring the expansion of the universe. Among the peculiar types of SNe Ia, 91T-like SN Ia represents the brightest class. It is easier to detect in the high-redshift Universe. In this work, we aim to identify and study 91T-like SNe discovered from high-redshift surveys. Our sample consists of approximately 400 high-redshift SNe~Ia from the Pan-STARRS1 Medium Deep Survey (PS1-MDS). We spectroscopically classified 16 91T-like SN candidates, further exploring their characteristics. We found that the decline rates of the light curves of 91T-like SNe tend to be slower than those of normal SNe Ia, consistent with their brighter luminosities. Their Hubble residuals also tend to be negative compared to that predicted from the cosmological model. The colors of 91T-like SNe do not show significant differences compared to normal SNe Ia, possibly due to the influence of dust in the galaxies. Regarding the host-galaxy mass, star formation rate, and specific star formation rate, we found that the host-galaxy mass of 91T-like SNe is not significantly different from that of normal SNe Ia. However, 91T-like SNe tend to appear in galaxies with higher star formation rates and specific star formation rates. Our results indicate that the high-redshift 91T-like SNe generally exhibit consistent properties with those from lower-redshift studies.

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