In physically realistic, scalar-field-based dynamical dark energy models (including, e.g., quintessence), one naturally expects the scalar field to couple to the rest of the model’s degrees of ...freedom. In particular, a coupling to the electromagnetic sector leads to a time (redshift) dependence in the fine-structure constant and a violation of the weak equivalence principle. Here we extend the previous
Euclid
forecast constraints on dark energy models to this enlarged (but physically more realistic) parameter space, and forecast how well
Euclid
, together with high-resolution spectroscopic data and local experiments, can constrain these models. Our analysis combines simulated
Euclid
data products with astrophysical measurements of the fine-structure constant,
α
, and local experimental constraints, and it includes both parametric and non-parametric methods. For the astrophysical measurements of
α
, we consider both the currently available data and a simulated dataset representative of Extremely Large Telescope measurements that are expected to be available in the 2030s. Our parametric analysis shows that in the latter case, the inclusion of astrophysical and local data improves the
Euclid
dark energy figure of merit by between 8% and 26%, depending on the correct fiducial model, with the improvements being larger in the null case where the fiducial coupling to the electromagnetic sector is vanishing. These improvements would be smaller with the current astrophysical data. Moreover, we illustrate how a genetic algorithms based reconstruction provides a null test for the presence of the coupling. Our results highlight the importance of complementing surveys like
Euclid
with external data products, in order to accurately test the wider parameter spaces of physically motivated paradigms.
Abstract
The Complete Calibration of the Color–Redshift Relation (C3R2) survey is obtaining spectroscopic redshifts in order to map the relation between galaxy color and redshift to a depth of
i
∼ ...24.5 (AB). The primary goal is to enable sufficiently accurate photometric redshifts for Stage
iv
dark energy projects, particularly Euclid and the Nancy Grace Roman Space Telescope (Roman), which are designed to constrain cosmological parameters through weak lensing. We present 676 new high-confidence spectroscopic redshifts obtained by the C3R2 survey in the 2017B–2019B semesters using the DEIMOS, LRIS, and MOSFIRE multiobject spectrographs on the Keck telescopes. Combined with the 4454 redshifts previously published by this project, the C3R2 survey has now obtained and published 5130 high-quality galaxy spectra and redshifts. If we restrict consideration to only the 0.2 <
z
p
< 2.6 range of interest for the Euclid cosmological goals, then with the current data release, C3R2 has increased the spectroscopic redshift coverage of the Euclid color space from 51% (as reported by Masters et al.) to the current 91%. Once completed and combined with extensive data collected by other spectroscopic surveys, C3R2 should provide the spectroscopic calibration set needed to enable photometric redshifts to meet the cosmology requirements for Euclid, and make significant headway toward solving the problem for Roman.
Context. Precise determination of stellar masses is necessary to test the validity of pre-main-sequence (PMS) stellar evolutionary models, whose predictions are in disagreement with measurements for ...masses below 1.2 M⊙. To improve such a test, and based on our previous studies, we selected the AB Doradus moving group (AB Dor-MG) as the best-suited association on which to apply radio-based high-precision astrometric techniques to study binary systems. Aims. We seek to determine precise estimates of the masses of a set of stars belonging to the AB Dor-MG using radio and infrared observations. Methods. We observed in phase-reference mode with the Very Large Array (VLA) at 5 GHz and with the European VLBI Network (EVN) at 8.4 GHz the stars HD 160934, EK Dra, PW And, and LO Peg. We also observed some of these stars with the near-infrared CCD AstraLux camera at the Calar Alto observatory to complement the radio observations. Results. We determine model-independent dynamical masses of both components of the star HD 160934, A and c, which are 0.70 ± 0.07 M⊙ and 0.45 ± 0.04 M⊙, respectively. We revised the orbital parameters of EK Dra and we determine a sum of the masses of the system of 1.38 ± 0.08 M⊙. We also explored the binarity of the stars LO Peg and PW And. Conclusions. We found observational evidence that PMS evolutionary models underpredict the mass of PMS stars by 10%−40%, as previously reported by other authors. We also inferred that the origin of the radio emission must be similar in all observed stars, that is, extreme magnetic activity of the stellar corona that triggers gyrosynchrotron emission from non-thermal, accelerated electrons.
Euclid preparation Barnett, R.; Warren, S. J.; Mortlock, D. J. ...
Astronomy and astrophysics (Berlin),
11/2019, Letnik:
631
Journal Article
Recenzirano
Odprti dostop
We provide predictions of the yield of 7 < z < 9 quasars from the Euclid wide survey, updating the calculation presented in the Euclid Red Book in several ways. We account for revisions to the ...Euclid near-infrared filter wavelengths; we adopt steeper rates of decline of the quasar luminosity function (QLF; Φ) with redshift, Φ ∝ 10k(z − 6), k = −0.72, and a further steeper rate of decline, k = −0.92; we use better models of the contaminating populations (MLT dwarfs and compact early-type galaxies); and we make use of an improved Bayesian selection method, compared to the colour cuts used for the Red Book calculation, allowing the identification of fainter quasars, down to JAB ∼ 23. Quasars at z > 8 may be selected from Euclid OYJH photometry alone, but selection over the redshift interval 7 < z < 8 is greatly improved by the addition of z-band data from, e.g., Pan-STARRS and LSST. We calculate predicted quasar yields for the assumed values of the rate of decline of the QLF beyond z = 6. If the decline of the QLF accelerates beyond z = 6, with k = −0.92, Euclid should nevertheless find over 100 quasars with 7.0 < z < 7.5, and ∼25 quasars beyond the current record of z = 7.5, including ∼8 beyond z = 8.0. The first Euclid quasars at z > 7.5 should be found in the DR1 data release, expected in 2024. It will be possible to determine the bright-end slope of the QLF, 7 < z < 8, M1450 < −25, using 8 m class telescopes to confirm candidates, but follow-up with JWST or E-ELT will be required to measure the faint-end slope. Contamination of the candidate lists is predicted to be modest even at JAB ∼ 23. The precision with which k can be determined over 7 < z < 8 depends on the value of k, but assuming k = −0.72 it can be measured to a 1σ uncertainty of 0.07.
ABSTRACT The Multi-conjugate Adaptive optics Demonstrator (MAD) is the first multiconjugated adaptive optics system at the Very Large Telescope (VLT). We present H and KS observations of the young ...massive cluster Trumpler14 revealing the power of MCAO systems by providing a homogeneous Strehl ratio over a large field of view. Mean Strehl ratios of 6.0 and 5.9per cent with maximum Strehl ratios of 9.8 and 12.6 per cent in H and KS, respectively, show significant improvement of the spatial point spread function (PSF) stability compared to single-conjugated adaptive optics systems. Photometry of our observations cover a dynamic range of 10mag including 2-3 times greater number of sources than comparable seeing-limited observations. The colour-magnitude diagram reveals that the massive cluster originated in a recent starburst-like event 1 ± 0.5Myr ago. We tentatively detect hints for an older population of 3Myr suggesting that low intensity star formation might have been going on in the Hii region for a few Myr. We derive the luminosity function and mass function between 0.1 and 3.2 M and identify a change in the power-law slope of the mass function at mc 0.53+0.12- 0.10M. The MF appears shallow with power-law slopes of Γ1=-0.50 ± 0.11 above mc and Γ2= 0.63 ± 0.32 below mc.
The Multi-conjugate Adaptive optics Demonstrator (MAD) is the first multiconjugated adaptive optics system at the Very Large Telescope (VLT). We present H and K
S observations of the young massive ...cluster Trumpler 14 revealing the power of MCAO systems by providing a homogeneous Strehl ratio over a large field of view. Mean Strehl ratios of 6.0 and 5.9 per cent with maximum Strehl ratios of 9.8 and 12.6 per cent in H and K
S, respectively, show significant improvement of the spatial point spread function (PSF) stability compared to single-conjugated adaptive optics systems. Photometry of our observations cover a dynamic range of ∼10 mag including 2-3 times greater number of sources than comparable seeing-limited observations. The colour-magnitude diagram reveals that the massive cluster originated in a recent starburst-like event 1 ± 0.5 Myr ago. We tentatively detect hints for an older population of 3 Myr suggesting that low intensity star formation might have been going on in the Hii region for a few Myr. We derive the luminosity function and mass function between 0.1 and 3.2 M⊙ and identify a change in the power-law slope of the mass function at m
c∼ 0.53+0.12
− 0.10 M⊙. The MF appears shallow with power-law slopes of Γ1=−0.50 ± 0.11 above m
c and Γ2= 0.63 ± 0.32 below m
c.
Context.Members of nearby moving groups are promising candidates for the detection of stellar or substellar companions by direct imaging. Mass estimates and magnitude measurements of detected ...companions to young stars are valuable input data to facilitate the refinement of existing pre-main-sequence stellar models. In this paper we report on our detection of a close companion to HD 160934, a young active star, SB1 spectroscopic binary, and suggested member of the AB Doradus moving group. Aims.We obtained high angular resolution images of nearby young stars, searching for close companions. In the case of HD 160934, direct imaging was combined with unresolved photometry to derive mass estimates. Methods.High angular resolution was achieved by means of the so-called “Lucky Imaging” technique, allowing direct imaging close to the diffraction limit in the SDSS z' band with a 2.2 m telescope. Our results are combined with pre-discovery HST archive data, own $UBV(RI)_{\rm C}$ broadband photometry, published JHK magnitudes, and available radial velocity measurements to constrain the physical properties of the HD 160934 close binary. Results.At an assumed age of ~80 Myr, we derive mass estimates of 0.69 $M_{\odot}$ and 0.57 $M_{\odot}$, respectively, for HD 160934 and its close companion. We suggest that the direct detection may be identical to the spectroscopically discovered companion, leading to a period estimate of ~8.5 years and a semimajor axis of $a\approx 4.5$ AU.
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