ORCID Profile
0000-0002-4043-2727
Current Organisation
Ruprecht Karls Universität Heidelberg
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Publisher: American Astronomical Society
Date: 20-01-2021
Publisher: Elsevier BV
Date: 07-2006
DOI: 10.1016/J.JAD.2006.02.019
Abstract: To assess the acceptability of routine screening for perinatal depression. Postnatal women (n=860) and health professionals (n=916) were surveyed after 3 years of routine perinatal (antenatal and postnatal) use of the Edinburgh Postnatal Depression Scale (EPDS). Over 90% of women had the screening explained to them and found the EPDS easy to complete 85% had no difficulties completing it. Discomfort with screening was significantly related to having a higher EPDS score. A majority of health professionals using the EPDS was comfortable and found it useful. The s le involved only maternity services supporting depression screening. In addition, the response rate from GPs was low. Routine screening with the EPDS is acceptable to most women and health professionals. Sensitive explanation, along with staff training and support, is essential in implementing depression screening.
Publisher: American Astronomical Society
Date: 30-01-2006
DOI: 10.1086/501005
Publisher: American Astronomical Society
Date: 04-2023
Abstract: We explore the chemodynamical properties of a s le of very metal-poor (VMP) stars selected from the Hamburg/ESO survey, matched with Gaia EDR3, in the phase space identified by the three integrals of motion ( L z , E , I 3 ). Disk and halo orbits are separated by using the criteria defined in Carollo & Chiba. We found 26 stars with [Fe/H] ≤ −2.5 possessing disk kinematics, of which 13 are extremely metal-poor. At these metallicities, the number of stars with disk kinematics is three times its retrograde counterpart. In the same range of metallicity we also identified 37 halo stars most tightly bound to the gravitational potential of the progenitor halo. The origins of these stars are investigated by comparing the observational results with simulated galaxies from the Aquarius Project and the IllustrisTNG simulations. We found two mechanisms of formation of VMP stars with disk kinematics: accretion from early satellites (which is dominant), and in situ formation. These stars are very old, with ages .5 Gyr ( z 5), and they are α -enriched. Accretion and in situ formation are also found for the retrograde counterparts, with accretion also being the dominant mode. Contributing accreted satellites have stellar masses in the range 10 6 –10 9 M ☉ and are very gas-rich. The most bound halo stars are the oldest detected, with a median age of ∼13.3 Gyr ( z ∼ 11), and are α -enriched. Our finding clearly shows that very old, VMP stars store important information on the first stages of assembly of our Galaxy and its halo.
Publisher: American Astronomical Society
Date: 30-04-2012
Publisher: Oxford University Press (OUP)
Date: 05-08-2020
Abstract: Large multiobject spectroscopic surveys require automated algorithms to optimize their observing strategy. One of the most ambitious upcoming spectroscopic surveys is the 4MOST survey. The 4MOST survey facility is a fibre-fed spectroscopic instrument on the VISTA telescope with a large enough field of view to survey a large fraction of the southern sky within a few years. Several Galactic and extragalactic surveys will be carried out simultaneously, so the combined target density will strongly vary. In this paper, we describe a new tiling algorithm that can naturally deal with the large target density variations on the sky and which automatically handles the different exposure times of targets. The tiling pattern is modelled as a marked point process, which is characterized by a probability density that integrates the requirements imposed by the 4MOST survey. The optimal tilling pattern with respect to the defined model is estimated by the tiles configuration that maximizes the proposed probability density. In order to achieve this maximization a simulated annealing algorithm is implemented. The algorithm automatically finds an optimal tiling pattern and assigns a tentative sky brightness condition and exposure time for each tile, while minimizing the total execution time that is needed to observe the list of targets in the combined input catalogue of all surveys. Hence, the algorithm maximizes the long-term observing efficiency and provides an optimal tiling solution for the survey. While designed for the 4MOST survey, the algorithm is flexible and can with simple modifications be applied to any other multiobject spectroscopic survey.
Publisher: American Astronomical Society
Date: 05-12-2016
Publisher: Springer Science and Business Media LLC
Date: 10-2022
DOI: 10.1007/S10686-022-09864-7
Abstract: We introduce the scientific motivations for the development of the Cassegrain U-Band Efficient Spectrograph (CUBES) that is now in construction for the Very Large Telescope. The assembled cases span a broad range of contemporary topics across Solar System, Galactic and extragalactic astronomy, where observations are limited by the performance of current ground-based spectrographs shortwards of 400 nm. A brief background to each case is presented and specific technical requirements on the instrument design that flow-down from each case are identified. These were used as inputs to the CUBES design, that will provide a factor of ten gain in efficiency for astronomical spectroscopy over 300-405 nm, at resolving powers of $$R~\\sim$$ R ∼ 24,000 and $$\\sim$$ ∼ 7,000. We include performance estimates that demonstrate the ability of CUBES to observe sources that are up to three magnitudes fainter than currently possible at ground-ultraviolet wavelengths, and we place its predicted performance in the context of existing facillities.
Publisher: American Astronomical Society
Date: 04-06-2009
Publisher: EDP Sciences
Date: 03-2020
DOI: 10.1051/0004-6361/201937228
Abstract: Context. Several new multi-object spectrographs are currently planned or under construction that are capable of observing thousands of Galactic and extragalactic objects simultaneously. Aims. In this paper we present a probabilistic fibre-to-target assignment algorithm that takes spectrograph targeting constraints into account and is capable of dealing with multiple concurrent surveys. We present this algorithm using the 4-m Multi-Object Spectroscopic Telescope (4MOST) as an ex le. Methods. The key idea of the proposed algorithm is to assign probabilities to fibre-target pairs. The assignment of probabilities takes the fibre positioner’s capabilities and constraints into account. Additionally, these probabilities include requirements from surveys and take the required exposure time, number density variation, and angular clustering of targets across each survey into account. The main advantage of a probabilistic approach is that it allows for accurate and easy computation of the target selection function for the different surveys, which involves determining the probability of observing a target, given an input catalogue. Results. The probabilistic fibre-to-target assignment allows us to achieve maximally uniform completeness within a single field of view. The proposed algorithm maximises the fraction of successfully observed targets whilst minimising the selection bias as a function of exposure time. In the case of several concurrent surveys, the algorithm maximally satisfies the scientific requirements of each survey and no specific survey is penalised or prioritised. Conclusions. The algorithm presented is a proposed solution for the 4MOST project that allows for an unbiased targeting of many simultaneous surveys. With some modifications, the algorithm may also be applied to other multi-object spectroscopic surveys.
Publisher: SPIE
Date: 09-08-2016
DOI: 10.1117/12.2232832
Publisher: SPIE
Date: 24-07-2014
DOI: 10.1117/12.2055826
Publisher: EDP Sciences
Date: 18-03-2016
Publisher: Oxford University Press (OUP)
Date: 06-2005
Publisher: American Astronomical Society
Date: 25-11-2015
Publisher: EDP Sciences
Date: 10-2022
DOI: 10.1051/0004-6361/202243811
Abstract: Context. The study of the oldest and most metal-poor stars in our Galaxy promotes our understanding of the Galactic chemical evolution and the beginning of Galaxy and star formation. However, they are notoriously difficult to find, with only seven stars at [Fe/H] −5.0 having been detected to date. Thus, the spectrophotometric data of 219 million sources which became available in the third Gaia Data Release comprise a very promising dataset for the identification of metal-poor stars. Aims. We want to use the low-resolution Gaia Blue Photometer/Red Photometer (BP/RP) spectra to identify metal-poor stars. Our primary aspiration is to help populate the poorly constrained tail of the metallicity distribution function of the stellar halo of the Galaxy. Methods. We developed a metal-poor candidate selection method based on flux ratios from the BP/RP Gaia spectra, using simulated synthetic spectra. Results. We found a relation between the relative iron abundance and the flux ratio of the Ca H & K region to that of the Hβ line. This relation is temperature and surface gravity dependent, and it holds for stars with 4800 K ≤ T eff ≤ 6300 K. We applied it to noisy simulated synthetic spectra and inferred [Fe/H] with an uncertainty of σ [Fe/H] ≲ 0.65 dex for −3 ≤ [Fe/H] ≤ 0.5 and G = 15–17 mag, which is sufficient to identify stars at [Fe/H] −2.0 reliably. We predict that by selecting stars with inferred [Fe/H] ≤ −2.5 dex, we can retrieve 80% of the stars with [Fe/H] ≤ −3 and have a success rate of about 50%, that is one in two stars we select would have [Fe/H] ≤ −3. We do not take into account the effect of reddening, so our method should only be applied to stars which are located in regions of low extinction.
Publisher: American Astronomical Society
Date: 09-2008
DOI: 10.1086/590327
Publisher: European Southern Observatory (ESO)
Date: 2019
Publisher: American Astronomical Society
Date: 13-12-2012
Publisher: European Southern Observatory (ESO)
Date: 2019
Publisher: American Astronomical Society
Date: 11-2005
DOI: 10.1086/444414
Publisher: American Astronomical Society
Date: 30-05-2013
Publisher: EDP Sciences
Date: 08-2017
Publisher: SPIE
Date: 29-08-2022
DOI: 10.1117/12.2629990
Publisher: SPIE
Date: 29-08-2022
DOI: 10.1117/12.2628965
No related grants have been discovered for Norbert Christlieb.