Two New Calcium-rich Gap Transients in Group and Cluster Environments
Two New Calcium-rich Gap Transients in Group and Cluster Environments
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DOI：
10.3847/1538-4357/836/1/60
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发表时间：
2016-12
期刊：
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通讯作者：
R. Lunnan;M. Kasliwal;Yi Cao;Yi Cao;L. Hangard;O. Yaron;J. Parrent;C. McCully;C. McCully;A. Gal-yam;J. Mulchaey;S. Ben-Ami;A. Filippenko;C. Fremling;A. Fruchter;D. Howell;D. Howell;J. Koda;T. Kupfer;S. Kulkarni;R. Laher;F. Masci;P. Nugent;P. Nugent;E. Ofek;M. Yagi;Lin Yan
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作者：
R. Lunnan;M. Kasliwal;Yi Cao;Yi Cao;L. Hangard;O. Yaron;J. Parrent;C. McCully;C. McCully;A. Gal-yam;J. Mulchaey;S. Ben-Ami;A. Filippenko;C. Fremling;A. Fruchter;D. Howell;D. Howell;J. Koda;T. Kupfer;S. Kulkarni;R. Laher;F. Masci;P. Nugent;P. Nugent;E. Ofek;M. Yagi;Lin Yan
我们介绍 Palomar Transient Factory 的发现以及 PTF11kmb 和 PTF12bho 的光度和光谱观测。我们表明，这两种瞬变都具有与富钙能隙瞬变类别一致的特性，特别是与普通超新星相比，峰值光度较低且快速演化，以及以[Ca ii]发射为主的星云光谱。这两个瞬变的一个显着特征是它们的宿主环境：PTF12bho 是后发星团中的一个星系团内瞬变，而 PTF11kmb 位于一个松散的星系群中，与最可能的宿主星系的物理偏移量约 150 kpc。 PTF12bho 的深斯巴鲁成像排除了潜在的宿主系统，而 PTF11kmb 的哈勃太空望远镜成像揭示了一个边缘对应物，如果真实存在，可能是背景星系或球状星团。我们表明，富钙能隙瞬变的偏移分布比超新星 Ia 甚至短硬伽马射线暴 (sGRB) 的偏移分布要极端得多。因此，如果偏移是由冲击引起的，则它们需要比 sGRB 更高的冲击速度和/或更长的合并时间。我们还表明，迄今为止发现的几乎所有富含钙的瞬变现象都存在于具有椭圆宿主星系的群和星团环境中，这表明它们的祖先群体非常古老；偏远位置的部分原因是这些环境在星系间相互作用后群内/星团内光中恒星比例最大。
We present the Palomar Transient Factory discoveries and the photometric and spectroscopic observations of PTF11kmb and PTF12bho. We show that both transients have properties consistent with the class of calcium-rich gap transients, specifically lower peak luminosities and rapid evolution compared to ordinary supernovae, and a nebular spectrum dominated by [Ca ii] emission. A striking feature of both transients is their host environments: PTF12bho is an intracluster transient in the Coma Cluster, while PTF11kmb is located in a loose galaxy group, at a physical offset ∼150 kpc from the most likely host galaxy. Deep Subaru imaging of PTF12bho rules out an underlying host system to a limit of , while Hubble Space Telescope imaging of PTF11kmb reveals a marginal counterpart that, if real, could be either a background galaxy or a globular cluster. We show that the offset distribution of Ca-rich gap transients is significantly more extreme than that seen for SNe Ia or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets are caused by a kick, they require higher kick velocities and/or longer merger times than sGRBs. We also show that almost all Ca-rich transients found to date are in group and cluster environments with elliptical host galaxies, indicating a very old progenitor population; the remote locations could partially be explained by these environments having the largest fraction of stars in the intragroup/intracluster light following galaxy–galaxy interactions.