Institution
European Southern Observatory
Facility•Garching bei München, Germany•
About: European Southern Observatory is a facility organization based out in Garching bei München, Germany. It is known for research contribution in the topics: Galaxy & Stars. The organization has 3594 authors who have published 16157 publications receiving 823095 citations. The organization is also known as: The European Southern Observatory,ESO & ESO.
Topics: Galaxy, Stars, Star formation, Redshift, Population
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the authors reported the discovery of the 10μ m silicate feature in emission in two luminous quasars with the Infrared Spectrograph of the Spitzer Space Telescope.
Abstract: According to the unified scheme, AGN are surrounded by a dust-torus, and the observed diversity of AGN properties results from the different orientations relative to our line of sight. The strong resonance of silicate dust at 10 μ m is therefore, as expected, seen in absorption towards many type-2 AGN. In type-1 AGN, it should be seen in emission because the hot inner surface of the dust torus becomes visible. However, this has not been observed so far, thus challenging the unification scheme or leading to exotic modifications of the dust-torus model. Here we report the discovery of the 10 μ m silicate feature in emission in two luminous quasars with the Infrared Spectrograph of the Spitzer Space Telescope.
172 citations
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TL;DR: In this paper, the authors observed the twin-jet radio galaxy 3C 296 with Chandra and detected X-ray emission from the nucleus, inner parts of the radio jet and from a small-scale thermal environment around the jet deceleration region.
Abstract: We have observed the twin-jet radio galaxy 3C 296 with Chandra. X-ray emission is detected from the nucleus, from the inner parts of the radio jet and from a small-scale thermal environment around the jet deceleration region. As we have found in previous observations of other twin-jet radio galaxies, the X-ray jet and a steep pressure gradient in the external thermal environment are associated with the region where strong bulk deceleration of the jet material is suggested by radio observations. Our observations provide additional evidence that the inner jets of twin-jet objects are always associated with a relatively cool, dense central X-ray emitting component with a short cooling time.
172 citations
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TL;DR: In this article, the authors compared the tension between H 0 to the value inferred from CMB observations assuming ΛCDM, making it important to check for potential systematic uncertainties in either approach.
Abstract: The most precise local measurements of H 0 rely on observations of Type Ia supernovae (SNe Ia) coupled with Cepheid distances to SN Ia host galaxies. Recent results have shown tension comparing H 0 to the value inferred from CMB observations assuming ΛCDM, making it important to check for potential systematic uncertainties in either approach. To date, precise local H 0 measurements have used SN Ia distances based on optical photometry, with corrections for light curve shape and colour. Here, we analyse SNe Ia as standard candles in the near-infrared (NIR), where luminosity variations in the supernovae and extinction by dust are both reduced relative to the optical. From a combined fit to 9 nearby calibrator SNe with host Cepheid distances from and 27 SNe in the Hubble flow, we estimate the absolute peak J magnitude M J = −18.524 ± 0.041 mag and H 0 = 72.8 ± 1.6 (statistical) ±2.7 (systematic) km s-1 Mpc-1 . The 2.2% statistical uncertainty demonstrates that the NIR provides a compelling avenue to measuring SN Ia distances, and for our sample the intrinsic (unmodeled) peak J magnitude scatter is just ~0.10 mag, even without light curve shape or colour corrections. Our results do not vary significantly with different sample selection criteria, though photometric calibration in the NIR may be a dominant systematic uncertainty. Our findings suggest that tension in the competing H 0 distance ladders is likely not a result of supernova systematics that could be expected to vary between optical and NIR wavelengths, like dust extinction. We anticipate further improvements in H 0 with a larger calibrator sample of SNe Ia with Cepheid distances, more Hubble flow SNe Ia with NIR light curves, and better use of the full NIR photometric data set beyond simply the peak J -band magnitude.
172 citations
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TL;DR: Observations of 13CO and C18O emission for a sample of four dust-enshrouded starbursts at redshifts of approximately two to three reveal that massive stars are more numerous in starburst events than in ordinary star-forming spiral galaxies.
Abstract: All measurements of cosmic star formation must assume an initial distribution of stellar masses-the stellar initial mass function-in order to extrapolate from the star-formation rate measured for typically rare, massive stars (of more than eight solar masses) to the total star-formation rate across the full stellar mass spectrum 1 . The shape of the stellar initial mass function in various galaxy populations underpins our understanding of the formation and evolution of galaxies across cosmic time 2 . Classical determinations of the stellar initial mass function in local galaxies are traditionally made at ultraviolet, optical and near-infrared wavelengths, which cannot be probed in dust-obscured galaxies2,3, especially distant starbursts, whose apparent star-formation rates are hundreds to thousands of times higher than in the Milky Way, selected at submillimetre (rest-frame far-infrared) wavelengths4,5. The 13C/18O isotope abundance ratio in the cold molecular gas-which can be probed via the rotational transitions of the 13CO and C18O isotopologues-is a very sensitive index of the stellar initial mass function, with its determination immune to the pernicious effects of dust. Here we report observations of 13CO and C18O emission for a sample of four dust-enshrouded starbursts at redshifts of approximately two to three, and find unambiguous evidence for a top-heavy stellar initial mass function in all of them. A low 13CO/C18O ratio for all our targets-alongside a well tested, detailed chemical evolution model benchmarked on the Milky Way 6 -implies that there are considerably more massive stars in starburst events than in ordinary star-forming spiral galaxies. This can bring these extraordinary starbursts closer to the 'main sequence' of star-forming galaxies 7 , although such main-sequence galaxies may not be immune to changes in initial stellar mass function, depending on their star-formation densities.
172 citations
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TL;DR: The ESPRESSO spectrograph as discussed by the authors was designed for ultra-high radial-velocity (RV) precision and extreme spectral fidelity with the aim of performing exoplanet research and fundamental astrophysical experiments with unprecedented precision and accuracy.
Abstract: Context. ESPRESSO is the new high-resolution spectrograph of ESO’s Very Large Telescope (VLT). It was designed for ultra-high radial-velocity (RV) precision and extreme spectral fidelity with the aim of performing exoplanet research and fundamental astrophysical experiments with unprecedented precision and accuracy. It is able to observe with any of the four Unit Telescopes (UTs) of the VLT at a spectral resolving power of 140 000 or 190 000 over the 378.2 to 788.7 nm wavelength range; it can also observe with all four UTs together, turning the VLT into a 16 m diameter equivalent telescope in terms of collecting area while still providing a resolving power of 70 000.Aims. We provide a general description of the ESPRESSO instrument, report on its on-sky performance, and present our Guaranteed Time Observation (GTO) program along with its first results.Methods. ESPRESSO was installed on the Paranal Observatory in fall 2017. Commissioning (on-sky testing) was conducted between December 2017 and September 2018. The instrument saw its official start of operations on October 1, 2018, but improvements to the instrument and recommissioning runs were conducted until July 2019.Results. The measured overall optical throughput of ESPRESSO at 550 nm and a seeing of 0.65″ exceeds the 10% mark under nominal astroclimatic conditions. We demonstrate an RV precision of better than 25 cm s−1 during a single night and 50 cm s−1 over several months. These values being limited by photon noise and stellar jitter shows that the performance is compatible with an instrumental precision of 10 cm s−1 . No difference has been measured across the UTs, neither in throughput nor RV precision.Conclusions. The combination of the large collecting telescope area with the efficiency and the exquisite spectral fidelity of ESPRESSO opens a new parameter space in RV measurements, the study of planetary atmospheres, fundamental constants, stellar characterization, and many other fields.
171 citations
Authors
Showing all 3617 results
Name | H-index | Papers | Citations |
---|---|---|---|
Robert C. Nichol | 187 | 851 | 162994 |
Richard S. Ellis | 169 | 882 | 136011 |
Rob Ivison | 166 | 1161 | 102314 |
Alvio Renzini | 162 | 908 | 95452 |
Timothy C. Beers | 156 | 934 | 102581 |
Krzysztof M. Gorski | 132 | 380 | 105912 |
Emanuele Daddi | 129 | 581 | 63187 |
P. R. Christensen | 127 | 313 | 88445 |
Mark Dickinson | 124 | 389 | 66770 |
Christopher W. Stubbs | 122 | 622 | 109429 |
Eva K. Grebel | 118 | 863 | 83915 |
Martin Asplund | 118 | 612 | 52527 |
Jesper Sollerman | 118 | 726 | 53436 |
E. F. van Dishoeck | 115 | 742 | 49190 |
Jørgen Christensen-Dalsgaard | 114 | 585 | 48272 |