THE SEARCH FOR Hi EMISSION AT z ≈ 0.4 IN GRAVITATIONALLY LENSED GALAXIES WITH THE GREEN BANK TELESCOPE
THE SEARCH FOR Hi EMISSION AT z ≈ 0.4 IN GRAVITATIONALLY LENSED GALAXIES WITH THE GREEN BANK TELESCOPE
复制标题
使用绿岸望远镜寻找 z ≈ 0.4 英寸引力透镜星系的高发射
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
S. Edel
中科院分区：
文献类型：
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作者：
L. Hunt;D. Pisano;S. Edel
中性氢（Hi）是星星形成的重要燃料，但由于发射微弱，现代仪器的灵敏度有限，以及低频的地面射频干扰（RFI），在高红移下很难被探测到。我们报告的第一次尝试使用引力透镜探测Hi线发射的三个引力透镜星系团阿贝尔773，两个在红移0.398和一个在z = 0.487，使用绿色银行望远镜。我们发现，一个自转速度为200 km s−1的星系的3σ上限是MH i = 6.58 × 109和1.5 × 1010 M，z = 0.398和z = 0.487。在z = 0.398和z = 0.487处的源的估计Hi质量比我们在相应红移处的检测限低3.7和3.30倍。为了便于这些观察，我们使用sigma限幅来去除窄和宽带RFI，但保留来自源的信号。我们能够使用我们的例程将频谱的噪声降低25%，而不是丢弃具有太多RFI的观测值。当10%或更少的积分包含RFI时，该例程最有效。这些技术可以用来研究高放大遥远星系中的Hi，否则这些星系太微弱而无法检测到。
Neutral hydrogen (Hi) provides a very important fuel for star formation, but is difficult to detect at high redshift due to weak emission, limited sensitivity of modern instruments, and terrestrial radio frequency interference (RFI) at low frequencies. We report the first attempt to use gravitational lensing to detect Hi line emission from three gravitationally lensed galaxies behind the cluster Abell 773, two at redshifts of 0.398 and one at z = 0.487, using the Green Bank Telescope. We find that a 3σ upper limit for a galaxy with a rotation velocity of 200 km s−1 is MH i = 6.58 × 109 and 1.5 × 1010 M⊙ at z = 0.398 and z = 0.487. The estimated Hi masses of the sources at z = 0.398 and z = 0.487 are factors of 3.7 and ∼30 times lower than our detection limits at the respective redshifts. To facilitate these observations we have used sigma-clipping to remove both narrow- and wideband RFI but retain the signal from the source. We are able to reduce the noise of the spectrum by ∼25% using our routine instead of discarding observations with too much RFI. The routine is most effective when ∼10% of the integrations or fewer contain RFI. These techniques can be used to study Hi in highly magnified distant galaxies that are otherwise too faint to detect.