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Author: Liu, Teng × Has files: Yes ×

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    The eROSITA extragalactic CalPV serendipitous catalog
    (Les Ulis : EDP Sciences, 2022) Liu, Teng; Merloni, Andrea; Wolf, Julien; Salvato, Mara; Reiprich, Thomas H.; Comparat, Johan; Arcodia, Riccardo; Lamer, Georg; Georgakakis, Antonis; Dwelly, Tom; Sanders, Jeremy; Buchner, Johannes; Haberl, Frank; Ramos-Ceja, Miriam E.; Wilms, Jörn; Nandra, Kirpal; Brunner, Hermann; Brusa, Marcella; Schwope, Axel; Robrade, Jan; Freyberg, Michael; Boller, Thomas; Maitra, Chandreyee; Veronica, Angie; Malyali, Adam
    Context. The eROSITA X-ray telescope on board the Spectrum-Roentgen-Gamma (SRG) observatory performed calibration and performance verification (CalPV) observations between September 2019 and December 2019, ahead of the planned 4-yr all-sky surveys. Most of them were deep, pointing-mode observations. Aims. We present here the X-ray catalog detected from the set of extra-galactic CalPV observations released to the public by the German eROSITA consortium, and the multiband counterparts of these X-ray sources. Methods. We developed a source detection method optimized for point-like X-ray sources by including extended X-ray emission in the background measurement. The multiband counterparts were identified using a Bayesian method from the CatWISE catalog. Results. Combining 11 CalPV fields, we present a catalog containing 9515 X-ray sources, whose X-ray fluxes were measured through spectral fitting. CatWISE counterparts are presented for 77% of the sources. Significant variabilities are found in 99 of the sources, which are also presented with this paper. Most of these fields show similar number counts of point sources as typical extragalactic fields, and a few harbor particular stellar populations.
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    Teleconnections among tipping elements in the Earth system
    (London : Nature Publ. Group, 2023) Liu, Teng; Chen, Dean; Yang, Lan; Meng, Jun; Wang, Zanchenling; Ludescher, Josef; Fan, Jingfang; Yang, Saini; Chen, Deliang; Kurths, Jürgen; Chen, Xiaosong; Havlin, Shlomo; Schellnhuber, Hans Joachim
    Tipping elements are components of the Earth system that may shift abruptly and irreversibly from one state to another at specific thresholds. It is not well understood to what degree tipping of one system can influence other regions or tipping elements. Here, we propose a climate network approach to analyse the global impacts of a prominent tipping element, the Amazon Rainforest Area (ARA). We find that the ARA exhibits strong correlations with regions such as the Tibetan Plateau (TP) and West Antarctic ice sheet. Models show that the identified teleconnection propagation path between the ARA and the TP is robust under climate change. In addition, we detect that TP snow cover extent has been losing stability since 2008. We further uncover that various climate extremes between the ARA and the TP are synchronized under climate change. Our framework highlights that tipping elements can be linked and also the potential predictability of cascading tipping dynamics.