4MOST: the 4-metre Multi-Object Spectroscopic Telescope project at preliminary design review

Jong, Roelof S. de; Barden, Samuel C.; Bellido-Tirado, Olga; Brynnel, Joar; Frey, Steffen; Giannone, Domenico; Haynes, Roger; Johl, Diana; Phillips, Daniel R.; Schnurr, O.; Walcher, Jakob; Winkler, Roland; Ansorge, Wolfgang R.; Feltzing, Sofia; McMahon, R. G.; Baker, Gabriella; Caillier, Patrick; Dwelly, T.; Gäessler, Wolfgang; Iwert, Olaf; Mandel, H.; Piskunov, Nikolai; Pragt, J.; Walton, N. A.; Bensby, T.; Bergemann, M.; Chiappini, Cristina; Christlieb, N.; Cioni, M. R. L.; Driver, Simon P.; Finoguenov, A.; Helmi, Amina; Irwin, M. J.; Kitaura, Francisco-Shu; Kneib, Jean-Paul; Liske, J.; Merloni, A.; Minchev, Ivan; Richard, Johan; Starkenburg, Else

doi:10.1117/12.2232832

Cited by 50 publications

(16 citation statements)

References 6 publications

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“…Synergies with existing and upcoming ground-based spectroscopic surveys will be essential to obtain radial velocities and stellar spectra for subsets of these stars (e.g. Dalton 2016;de Jong et al 2016;Kunder et al 2017;Martell et al 2017). For what concerns HVSs, Marchetti et al (2018) shows how the majority of HVSs expected to be found in the Gaia catalogue are actually fainter than the limiting magnitude for radial velocities in DR2.…”

Section: Discussionmentioning

confidence: 99%

Gaia DR2 in 6D: searching for the fastest stars in the Galaxy

Marchetti

Rossi

Brown

2018

Monthly Notices of the Royal Astronomical Society

118

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We search for the fastest stars in the subset of stars with radial velocity measurements of the second data release (DR2) of the European Space Agency mission Gaia . Starting from the observed positions, parallaxes, proper motions, and radial velocities, we construct the distance and total velocity distribution of more than 7 million stars in our Milky Way, deriving the full 6D phase space information in Galactocentric coordinates. These information are shared in a catalogue, publicly available at http://home.strw.leidenuniv. nl/~marchetti/research.html. To search for unbound stars, we then focus on stars with a probability greater than 50% of being unbound from the Milky Way. This cut results in a clean sample of 125 sources with reliable astrometric parameters and radial velocities. Of these, 20 stars have probabilities greater than 80 % of being unbound from the Galaxy. On this latter sub-sample, we perform orbit integration to characterize the stars' orbital parameter distributions. As expected given the relatively small sample size of bright stars, we find no hypervelocity star candidates, stars that are moving on orbits consistent with coming from the Galactic Centre. Instead, we find 7 hyper-runaway star candidates, coming from the Galactic disk. Surprisingly, the remaining 13 unbound stars cannot be traced back to the Galaxy, including two of the fastest stars (around 700 km s −1 ). If conformed, these may constitute the tip of the iceberg of a large extragalactic population or the extreme velocity tail of stellar streams.

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Section: Discussionmentioning

confidence: 99%

Gaia DR2 in 6D: searching for the fastest stars in the Galaxy

Marchetti

Rossi

Brown

2018

Monthly Notices of the Royal Astronomical Society

118

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“…but straightforward extension of our main forecasts 7 . Unfortunately, there will be little expected overlap between DESI and HIRAX, which respecitvely lie in the Northern and Southern hemispheres; however, surveys such as 4MOST [117] and the proposed Southern spectroscopic survey [129] will obtain similar samples of ELGs and QSOs with large overlaps with HIRAX. For simplicity, in the following we will adopt the population and clustering statistics for DESI quoted in [18] while assuming full overlap with HIRAX, with the assumption that the aforementioned spectroscopic surveys will be qualitatively similar.…”

Section: B Constraints From Cross-correlating With Hiraxmentioning

confidence: 99%

Synergies between radio, optical and microwave observations at high redshift

Chen

Castorina

White

et al. 2019

J. Cosmol. Astropart. Phys.

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We study synergies between three promising methods to measure 2 < z < 5 largescale structure in the next decade. Optical spectroscopic surveys are the most mature, but become increasingly difficult at z > 2 and suffer from interloper problems even for spectroscopic surveys. Intensity mapping of the 21-cm signal can cover large volumes with exquisite fidelity, but is limited both by loss of information to foreground cleaning and by lack of knowledge of the mean signal. Cosmic microwave background (CMB) lensing is theoretically very clean, but ultimately measures just the projected variations in density. We find that cross-correlation between optical and radio can significantly improve the measurement of growth rate. Combining these with the CMB provides a promising avenue to detecting modified gravity at high redshifts, in particular by independently probing the Weyl and Newtonian potentials and by strengthening control of systematics. We find that cross-correlating a Stage ii 21-cm survey with DESI quasars with a reasonable brightness temperature prior could enable measurements of the growth rate f σ 8 at sub 3% and sub 8% levels at z = 3, 4, representing a factor of 4 and 8 improvement over constraints obtainable from DESI quasars alone. Similarly, cross-correlating 21-cm data with a futuristic LBG survey to m U V < 24.5 over 1000 square degrees will make possible f σ 8 measurements at close to 1% at z = 3 and 3% at z = 4, and improve similar constraints at z = 5 by close to a factor of 3 to sub-10% precision. Combining the above with CMB lensing from a Stage 4 CMB survey and LSST data can additionally constrain the gravitational slip γ parameter to similar precision at these redshifts, enabling us to test the predictions of general relativity at large scales.

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“…Galaxy survey [41]. We consider this sample in order to explore the benefit of having a full area overlap with southern-hemisphere, ground-based CMB experiments.…”

Section: Desi 4mostmentioning

confidence: 99%

Bias of damped Lyman-α systems from their cross-correlation with CMB lensing

Alonso¹,

Colosimo²,

Font-Ribera³

et al. 2018

J. Cosmol. Astropart. Phys.

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We cross-correlate the positions of damped Lyman-α systems (DLAs) and their parent quasar catalog with a convergence map derived from the Planck cosmic microwave background (CMB) temperature data. We make consistent detections of the lensing signal of both samples in both Fourier and configuration space. By interpreting the excess signal present in the DLA catalog with respect to the parent quasar catalog as caused by the large scale structure traced by DLAs, we are able to infer the bias of these objects: b DLA = 2.6±0.9. These results are consistent with previous measurements made in cross-correlation with the Lyman-α forest, although the current noise in the lensing data and the low number density of DLAs limits the constraining power of this measurement. We discuss the robustness of the analysis with respect to a number different systematic effects and forecast prospects of carrying out this measurement with data from future experiments.

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4MOST: the 4-metre Multi-Object Spectroscopic Telescope project at preliminary design review

Cited by 50 publications

References 6 publications

Gaia DR2 in 6D: searching for the fastest stars in the Galaxy

Gaia DR2 in 6D: searching for the fastest stars in the Galaxy

Synergies between radio, optical and microwave observations at high redshift

Bias of damped Lyman-α systems from their cross-correlation with CMB lensing

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