The LOFAR long baseline snapshot calibrator survey
The LOFAR long baseline snapshot calibrator survey
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LOFAR 长基线快照校准器调查
DOI：
10.1051/0004-6361/201425042
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发表时间：
2014
影响因子：
4.8
通讯作者：
A. Zensus
中科院分区：
文献类型：
--
作者：
J. Mold'on;A. Deller;O. Wucknitz;N. Jackson;A. Drabent;T. Carozzi;J. Conway;A. Kapińska;P. McKean;L. Morabito;E. Varenius;P. Zarka;J. Anderson;A. Asgekar;I. Avruch;M. Bell;M. Bentum;G. Bernardi;P. Best;L. Bîrzan;J. Bregman;F. Breitling;J. Broderick;M. Bruggen;H. Butcher;D. Carbone;B. Ciardi;F. Gasperin;E. D. Geus;S. Duscha;J. Eisloffel;D. Engels;H. Falcke;R. Fallows;R. Fender;C. Ferrari;W. Frieswijk;M. Garrett;J. Grießmeier;A. Gunst;J. Hamaker;T. Hassall;G. Heald;M. Hoeft;E. Juette;A. Karastergiou;V. Kondratiev;M. Kramer;M. Kuniyoshi;G. Kuper;P. Maat;G. Mann;S. Markoff;R. McFadden;D. McKay;R. Morganti;H. Munk;M. Norden;A. Offringa;E. Orrù;H. Paas;M. Pandey;R. Pizzo;A. Polatidis;W. Reich;H. Rottgering;A. Rowlinson;A. Scaife;D. Schwarz;J. Sluman;O. Smirnov;B. Stappers;M. Steinmetz;M. Tagger;Y. Tang;C. Tasse;S. Thoudam;M. C. Toribio;R. Vermeulen;C. Vocks;R. Weeren;S. White;M. Wise;S. Yatawatta;A. Zensus
目标。开发了一种为国际LOFAR定位校准源的有效方法，并用于确定140 MHz亚弧秒观测空中可用校准源的平均密度。方法：研究方法。我们利用LOFAR的多波束能力，利用完整的国际LOFAR阵列进行了一次快速且计算成本低廉的调查。使用现有的星表，根据325兆赫弧分尺度的通量密度预先选择了源。通过每小时观察12组点位中的每组中的30个不同的源，我们能够在两小时内检查630个源，以确定它们是否具有足够明亮的紧凑组件，可以用作LOFAR延迟校准器。结果。超过40%的观测源是在国际台站之间的多条基线上探测到的，其中86个被归类为满意的校准器。我们表明，在140 MHz处，平坦的低频频谱(从74到325 MHz)是预测紧凑性的最好指标。我们从我们的样本中推断出，天空中足够明亮的校准器密度足以使用现有方法校准国际LOFAR的色散和非色散延迟，密度为每平方度1.0。结论。观测到的令人满意的延迟校准源的密度意味着，国际LOFAR应该可以在天空中的几乎任何一点进行观测，前提是在观测之前使用本文所述的方法进行快速有效的搜索，以确定最佳校准器。
Aims. An efficient means of locating calibrator sources for International LOFAR is developed and used to determine the average density of usable calibrator sources on the sky for subarcsecond observations at 140 MHz. Methods. We used the multi-beaming capability of LOFAR to conduct a fast and computationally inexpensive survey with the full International LOFAR array. Sources were pre-selected on the basis of 325 MHz arcminute-scale flux density using existing catalogues. By observing 30 different sources in each of the 12 sets of pointings per hour, we were able to inspect 630 sources in two hours to determine if they possess a sufficiently bright compact component to be usable as LOFAR delay calibrators. Results. Over 40% of the observed sources are detected on multiple baselines between international stations and 86 are classified as satisfactory calibrators. We show that a flat low-frequency spectrum (from 74 to 325 MHz) is the best predictor of compactness at 140 MHz. We extrapolate from our sample to show that the density of calibrators on the sky that are sufficiently bright to calibrate dispersive and non-dispersive delays for the International LOFAR using existing methods is 1.0 per square degree. Conclusions. The observed density of satisfactory delay calibrator sources means that observations with International LOFAR should be possible at virtually any point in the sky, provided that a fast and efficient search using the methodology described here is conducted prior to the observation to identify the best calibrator.
M82 核在 118 MHz 和 154 MHz 下的亚弧秒国际 LOFAR 射电图像
影响因子：
6.5
作者：
Varenius;Adebahr;Dettmar;Brüggen
通讯作者：
Brüggen
影响因子：
6.5
作者：
van Haarlem, M. P.;Wise, M. W.;van Zwieten, J.
通讯作者：
van Zwieten, J.