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The Close AGN Reference Survey (CARS). What is causing Mrk 1018's return to the shadows after 30 years?
Combes, F.; Scharwächter, J.; Eckart, A. +11 more
We recently discovered that the active galactic nucleus (AGN) of Mrk 1018 has changed optical type again after 30 yr as a type 1 AGN. Here we combine Chandra, NuStar, Swift, Hubble Space Telescope and ground-based observations to explore the cause of this change. The 2-10 keV flux declines by a factor of ~8 between 2010 and 2016. We show with our …
Detecting direct collapse black holes: making the case for CR7
van den Bosch, Frank C.; Natarajan, Priyamvada; Zackrisson, Erik +4 more
We propose that one of the sources in the recently detected system CR7 by Sobral et al. through spectrophotometric measurements at z = 6.6 harbours a direct collapse black hole (DCBH). We argue that the LW radiation field required for direct collapse in source A is provided by sources B and C. By tracing the LW production history and star formatio…
Explosive Chromospheric Evaporation in a Circular-ribbon Flare
Guo, Y.; Li, D.; Ji, H. S. +3 more
In this paper, we report our multiwavelength observations of the C4.2 circular-ribbon flare in active region (AR) 12434 on 2015 October 16. The short-lived flare was associated with positive magnetic polarities and a negative polarity inside, as revealed by the photospheric line-of-sight magnetograms. Such a magnetic pattern is strongly indicative…
The ATLASGAL survey: distribution of cold dust in the Galactic plane. Combination with Planck data
Menten, K. M.; Weiss, A.; Henning, Th. +9 more
Context. Sensitive ground-based submillimeter surveys, such as ATLASGAL, provide a global view on the distribution of cold dense gas in the Galactic plane at up to two-times better angular-resolution compared to recent space-based surveys with Herschel. However, a drawback of ground-based continuum observations is that they intrinsically filter em…
A shock front at the radio relic of Abell 2744
Kneib, J. -P.; Eckert, D.; Vazza, F. +5 more
Radio relics are Mpc-scale diffuse radio sources at the peripheries of galaxy clusters which are thought to trace outgoing merger shocks. We present XMM-Newton and Suzaku observations of the galaxy cluster Abell 2744 (z = 0.306), which reveal the presence of a shock front 1.5 Mpc east of the cluster core. The surface-brightness jump coincides with…
The Correlation between Metallicity and Debris Disk Mass
Rieke, George H.; Gáspár, András; Ballering, Nicholas
We find that the initial dust masses in planetary debris disks are correlated with the metallicities of their central stars. We compiled a large sample of systems, including Spitzer, the Herschel DUNES and DEBRIS surveys, and WISE debris disk candidates. We also merged 33 metallicity catalogs to provide homogeneous [Fe/H] and {σ }[{Fe/{…
Understanding star formation in molecular clouds. III. Probability distribution functions of molecular lines in Cygnus X
Hill, T.; Schneider, N.; Ossenkopf, V. +11 more
The probability distribution function of column density (N-PDF) serves as a powerful tool to characterise the various physical processes that influence the structure of molecular clouds. Studies that use extinction maps or H2 column-density maps (N) that are derived from dust show that star-forming clouds can best be characterised by lo…
Whistler emission in the separatrix regions of asymmetric magnetic reconnection
André, M.; Vaivads, A.; Khotyaintsev, Yu. V. +1 more
At Earth's dayside magnetopause asymmetric magnetic reconnection occurs between the cold dense magnetosheath plasma and the hot tenuous magnetospheric plasma, which differs significantly from symmetric reconnection. During magnetic reconnection the separatrix regions are potentially unstable to a variety of instabilities. In this paper observation…
Rest-frame Optical Emission Lines in z ∼ 3.5 Lyman-break-selected Galaxies: The Ubiquity of Unusually High [OIII]/Hβ Ratios at 2 Gyr
Oesch, P. A.; van Dokkum, P.; Illingworth, G. D. +6 more
We present K-band spectra of rest-frame optical emission lines for 24 star-forming galaxies at z ∼ 3.2-3.7 using MOSFIRE on the Keck I telescope. Strong rest-frame optical [O III] and Hβ emission lines were detected in 18 Lyman break galaxies (LBGs). The median flux ratio of [O III]λ5007 to Hβ is {5.1}-0.5+0.5. This is a fact…
VISION - Vienna survey in Orion. I. VISTA Orion A Survey
Kainulainen, Jouni; Meingast, Stefan; Alves, João +17 more
Context. Orion A hosts the nearest massive star factory, thus offering a unique opportunity to resolve the processes connected with the formation of both low- and high-mass stars. Here we present the most detailed and sensitive near-infrared (NIR) observations of the entire molecular cloud to date.
Aims: With the unique combination of high im…