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End date: 2022 × Start date: 2022 × End date: 2024 × Start date: 2020 × WGL Institute: AIP ×

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    Gaia Early Data Release 3: Gaia photometric science alerts
    (Les Ulis : EDP Sciences, 2021) Hodgkin, S.T.; Harrison, D.L.; Breedt, E.; Wevers, T.; Rixon, G.; Delgado, A.; Yoldas, A.; Kostrzewa-Rutkowska, Z.; Wyrzykowski, Ł.; van Leeuwen, M.; Blagorodnova, N.; Serraller, I.; Steeghs, D.; Sullivan, M.; Szabados, L.; Szegedi-Elek, E.; Tisserand, P.; Tomasella, L.; van Velzen, S.; Whitelock, P.A; Wilson, R.W.; Campbell, H.; Young, D.R.; Eappachen, D.; Fraser, M.; Ihanec, N.; Koposov, S.E.; Kruszyńska, K.; Marton, G.; Rybicki, K.A.; Brown, A.G.A.; Burgess, P. W.; Busso, G.; Cowell, S.; De Angeli, F.; Diener, C.; Evans, D.W.; Gilmore, G.; Holland, G.; Jonker, P.G.; van Leeuwen, F.; Mignard, F.; Osborne, P.J.; Portell, J.; Prusti, T.; Richards, P.J.; Riello, M.; Seabroke, G.M.; Walton, N.A.; Ábrahám, Péter; Altavilla, G.; Baker, S.G.; Bastian, U.; O'Brien, P.; de Bruijne, J.; Butterley, T.; Carrasco, J.M.; Castañeda, J.; Clark, J.S.; Clementini, G.; Copperwheat, C.M.; Cropper, M.; Damljanovic, G.; Davidson, M.; Davis, C.J.; Dennefeld, M.; Dhillon, V.S.; Dolding, C.; Dominik, M.; Esquej, P.; Eyer, L.; Fabricius, C.; Fridman, M.; Froebrich, D.; Garralda, N.; Gomboc, A.; González-Vidal, J.J.; Guerra, R.; Hambly, N.C.; Hardy, L.K.; Holl, B.; Hourihane, A.; Japelj, J.; Kann, D.A.; Kiss, C.; Knigge, C.; Kolb, U.; Komossa, S.; Kóspál, Á.; Kovács, G.; Kun, M.; Leto, G.; Lewis, F.; Littlefair, S.P.; Mahabal, A.A.; Mundell, C.G.; Nagy, Z.; Padeletti, D.; Palaversa, L.; Pigulski, A.; Pretorius, M.L.; van Reeven, W.; Ribeiro, V.A.R.M.; Roelens, M.; Rowell, N.; Schartel, N.; Scholz, A.; Schwope, A.; Sipőcz, B.M.; Smartt, S.J.; Smith, M.D.
    Context. Since July 2014, the Gaia mission has been engaged in a high-spatial-resolution, time-resolved, precise, accurate astrometric, and photometric survey of the entire sky. Aims. We present the Gaia Science Alerts project, which has been in operation since 1 June 2016. We describe the system which has been developed to enable the discovery and publication of transient photometric events as seen by Gaia. Methods. We outline the data handling, timings, and performances, and we describe the transient detection algorithms and filtering procedures needed to manage the high false alarm rate. We identify two classes of events: (1) sources which are new to Gaia and (2) Gaia sources which have undergone a significant brightening or fading. Validation of the Gaia transit astrometry and photometry was performed, followed by testing of the source environment to minimise contamination from Solar System objects, bright stars, and fainter near-neighbours. Results. We show that the Gaia Science Alerts project suffers from very low contamination, that is there are very few false-positives. We find that the external completeness for supernovae, CE = 0.46, is dominated by the Gaia scanning law and the requirement of detections from both fields-of-view. Where we have two or more scans the internal completeness is CI = 0.79 at 3 arcsec or larger from the centres of galaxies, but it drops closer in, especially within 1 arcsec. Conclusions. The per-Transit photometry for Gaia transients is precise to 1% at G = 13, and 3% at G = 19. The per-Transit astrometry is accurate to 55 mas when compared to Gaia DR2. The Gaia Science Alerts project is one of the most homogeneous and productive transient surveys in operation, and it is the only survey which covers the whole sky at high spatial resolution (subarcsecond), including the Galactic plane and bulge. © S. T. Hodgkin et al. 2021.
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    Abundance-age relations with red clump stars in open clusters
    (Les Ulis : EDP Sciences, 2021) Casamiquela, L.; Soubiran, C.; Jofré, P.; Chiappini, C.; Lagarde, N.; Tarricq, Y.; Carrera, R.; Jordi, C.; Balaguer-Núñez, L.; Carbajo-Hijarrubia, J.; Blanco-Cuaresma, S.
    Context. Precise chemical abundances coupled with reliable ages are key ingredients to understanding the chemical history of our Galaxy. Open clusters (OCs) are useful for this purpose because they provide ages with good precision. Aims. The aim of this work is to investigate the relation between different chemical abundance ratios and age traced by red clump (RC) stars in OCs. Methods. We analyzed a large sample of 209 reliable members in 47 OCs with available high-resolution spectroscopy. We applied a differential line-by-line analysis, performing a comprehensive chemical study of 25 chemical species. This sample is among the largest samples of OCs homogeneously characterized in terms of atmospheric parameters, detailed chemistry, and age. Results. In our metallicity range (-0.2 < [M/H] < +0.2) we find that while most Fe-peak and α elements show a flat dependence on age, the s-process elements show a decreasing trend with increasing age with a remarkable knee at 1 Gyr. For Ba, Ce, Y, Mo, and Zr, we find a plateau at young ages (< 1 Gyr). We investigate the relations between all possible combinations among the computed chemical species and age. We find 19 combinations with significant slopes, including [Y/Mg] and [Y/Al]. The ratio [Ba/α] shows the most significant correlation. Conclusions. We find that the [Y/Mg] relation found in the literature using solar twins is compatible with the one found here in the solar neighborhood. The age-abundance relations in clusters at large distances(d > 1 kpc) show larger scatter than those in clusters in the solar neighborhood, particularly in the outer disk. We conclude that, in addition to pure nucleosynthetic arguments, the complexity of the chemical space introduced by the Galactic dynamics must be taken into account in order to understand these relations, especially outside of the local bubble. © L. Casamiquela et al. 2021.
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    The coherent motion of Cen A dwarf satellite galaxies remains a challenge for ΛcDM cosmology
    (Les Ulis : EDP Sciences, 2021) Müller, Oliver; Pawlowski, Marcel S.; Lelli, Federico; Fahrion, Katja; Rejkuba, Marina; Hilker, Michael; Kanehisa, Jamie; Libeskind, Noam; Jerjen, Helmut
    The plane-of-satellites problem is one of the most severe small-scale challenges for the standard Λ cold dark matter (ΛCDM) cosmological model: Several dwarf galaxies around the Milky Way and Andromeda co-orbit in thin, planar structures. A similar case has been identified around the nearby elliptical galaxy Centaurus A (Cen A). In this Letter, we study the satellite system of Cen A, adding twelve new galaxies with line-of-sight velocities from VLT/MUSE observations. We find that 21 out of 28 dwarf galaxies with measured velocities share a coherent motion. Similarly, flattened and coherently moving structures are found only in 0.2% of Cen A analogs in the Illustris-TNG100 cosmological simulation, independently of whether we use its dark-matter-only or hydrodynamical run. These analogs are not co-orbiting, and they arise only by chance projection, thus they are short-lived structures in such simulations. Our findings indicate that the observed co-rotating planes of satellites are a persistent challenge for ΛCDM, which is largely independent from baryon physics. © O. Müller et al. 2021.
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    The MUSE Extremely Deep Field: The cosmic web in emission at high redshift
    (Les Ulis : EDP Sciences, 2021) Bacon, Roland; Mary, David; Garel, Thibault; Blaizot, Jeremy; Maseda, Michael; Schaye, Joop; Wisotzki, Lutz; Conseil, Simon; Brinchmann, Jarle; Leclercq, Floriane; Abril-Melgarejo, Valentina; Boogaard, Leindert; Bouché, Nicolas; Contini, Thierry; Feltre, Anna; Guiderdoni, Bruno; Herenz, Christian; Kollatschny, Wolfram; Kusakabe, Haruka; Matthee, Jorryt; Michel-Dansac, Léo; Nanayakkara, Themiya; Richard, Johan; Roth, Martin; Schmidt, Kasper B.; Steinmetz, Matthias; Tresse, Laurence; Urrutia, Tanya; Verhamme, Anne; Weilbacher, Peter M.; Zabl, Johannes; Zoutendijk, Sebastiaan L.
    We report the discovery of diffuse extended Lyα emission from redshift 3.1 to 4.5, tracing cosmic web filaments on scales of 2.5-4 cMpc. These structures have been observed in overdensities of Lyα emitters in the MUSE Extremely Deep Field, a 140 h deep MUSE observation located in the Hubble Ultra-Deep Field. Among the 22 overdense regions identified, five are likely to harbor very extended Lyα emission at high significance with an average surface brightness of 5  ×  10-20 erg s-1 cm-2 arcsec-2. Remarkably, 70% of the total Lyα luminosity from these filaments comes from beyond the circumgalactic medium of any identified Lyα emitter. Fluorescent Lyα emission powered by the cosmic UV background can only account for less than 34% of this emission at z  ≈  3 and for not more than 10% at higher redshift. We find that the bulk of this diffuse emission can be reproduced by the unresolved Lyα emission of a large population of ultra low-luminosity Lyα emitters (< 1040 erg s-1), provided that the faint end of the Lyα luminosity function is steep (α ⪅ -1.8), it extends down to luminosities lower than 1038 -  1037 erg s-1, and the clustering of these Lyα emitters is significant (filling factor < 1/6). If these Lyα emitters are powered by star formation, then this implies their luminosity function needs to extend down to star formation rates < 10-4M yr-1. These observations provide the first detection of the cosmic web in Lyα emission in typical filamentary environments and the first observational clue indicating the existence of a large population of ultra low-luminosity Lyα emitters at high redshift. © R. Bacon et al. 2021.
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    A comparison between X-shooter spectra and PHOENIX models across the HR-diagram
    (Les Ulis : EDP Sciences, 2021) Lançon, A.; Gonneau, A.; Verro, K.; Prugniel, P.; Arentsen, A.; Trager, S.C.; Peletier, R.; Chen, Y.-P.; Coelho, P.; Falcón-Barroso, J.; Hauschildt, P.; Husser, T.-O.; Jain, R.; Lyubenova, M.; Martins, L.; Sánchez Blázquez, P.; Vazdekis, A.
    Aims. The path towards robust near-infrared extensions of stellar population models involves the confrontation between empirical and synthetic stellar spectral libraries across the wavelength ranges of photospheric emission. Indeed, the theory of stellar emission enters all population synthesis models, even when this is only implicit in the association of fundamental stellar parameters with empirical spectral library stars. With its near-ultraviolet to near-infrared coverage, the X-shooter Spectral Library (XSL) allows us to examine to what extent models succeed in reproducing stellar energy distributions (SEDs) and stellar absorption line spectra simultaneously. Methods. As a first example, this study compares the stellar spectra of XSL with those of the Göttingen Spectral Library, which are based on the PHOENIX synthesis code. The comparison was carried out both separately in the three arms of the X-shooter spectrograph known as UVB, VIS and NIR, and jointly across the whole spectrum. We did not discard the continuum in these comparisons; only reddening was allowed to modify the SEDs of the models. Results. When adopting the stellar parameters published with data release DR2 of XSL, we find that the SEDs of the models are consistent with those of the data at temperatures above 5000 K. Below 5000 K, there are significant discrepancies in the SEDs. When leaving the stellar parameters free to adjust, satisfactory representations of the SEDs are obtained down to about 4000 K. However, in particular below 5000 K and in the UVB spectral range, strong local residuals associated with intermediate resolution spectral features are then seen; the necessity of a compromise between reproducing the line spectra and reproducing the SEDs leads to dispersion between the parameters favored by various spectral ranges. We describe the main trends observed and we point out localized offsets between the parameters preferred in this global fit to the SEDs and the parameters in DR2. These depend in a complex way on the position in the Hertzsprung-Russell diagram (HRD). We estimate the effect of the offsets on bolometric corrections as a function of position in the HRD and use this for a brief discussion of their impact on the studies of stellar populations. A review of the literature shows that comparable discrepancies are mentioned in studies using other theoretical and empirical libraries. © A. Lançon et al. 2021.
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    Probing the structure of a massive filament: ArTéMiS 350 and 450 μm mapping of the integral-shaped filament in Orion A
    (Les Ulis : EDP Sciences, 2021) Schuller, F.; André, Ph.; Shimajiri, Y.; Zavagno, A.; Peretto, N.; Arzoumanian, D.; Csengeri, T.; Könyves, V.; Palmeirim, P.; Pezzuto, S.; Rigby, A.; Roussel, H.; Ajeddig, H.; Dumaye, L.; P. Gallais, P.; Le Pennec, J.; Martignac, J.; Mattern, M.; Revéret, V.; Rodriguez, L.; Talvard, M.
    Context. The Orion molecular cloud is the closest region of high-mass star formation. It is an ideal target for investigating the detailed structure of massive star-forming filaments at high resolution and the relevance of the filament paradigm for the earliest stages of intermediate- to high-mass star formation. Aims. Within the Orion A molecular cloud, the integral-shaped filament (ISF) is a prominent, degree-long structure of dense gas and dust with clear signs of recent and ongoing high-mass star formation. Our aim is to characterise the structure of this massive filament at moderately high angular resolution (8′′ or ~0.016 pc) in order to measure the intrinsic width of the main filament, down to scales well below 0.1 pc, which has been identified as the characteristic width of filaments. Methods. We used the ArTéMiS bolometer camera at APEX to map a ~0.6 × 0.2 deg2 region covering OMC-1, OMC-2, and OMC-3 at 350 and 450 μm. We combined these data with Herschel-SPIRE maps to recover extended emission. The combined Herschel-ArTéMiS maps provide details on the distribution of dense cold material, with a high spatial dynamic range, from our 8′′ resolution up to the transverse angular size of the map, ~10-15′. By combining Herschel and ArTéMiS data at 160, 250, 350, and 450 μm, we constructed high-resolution temperature and H2 column density maps. We extracted radial intensity profiles from the column density map in several representative portions of the ISF, which we fitted with Gaussian and Plummer models to derive their intrinsic widths. We also compared the distribution of material traced by ArTéMiS with that seen in the higher-density tracer N2H+(1-0) that was recently observed with the ALMA interferometer. Results. All the radial profiles that we extracted show a clear deviation from a Gaussian, with evidence for an inner plateau that had not previously been seen clearly using Herschel-only data. We measure intrinsic half-power widths in the range 0.06-0.11 pc. This is significantly larger than the Gaussian widths measured for fibres seen in N2H+, which probably only traces the dense innermost regions of the large-scale filament. These half-power widths are within a factor of two of the value of ~0.1 pc found for a large sample of nearby filaments in various low-mass star-forming regions, which tends to indicate that the physical conditions governing the fragmentation of pre-stellar cores within transcritical or supercritical filaments are the same over a large range of masses per unit length. © F. Schuller et al. 2021.
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    The tully-fisher relation in dense groups at z ∼ 0.7 in the MAGIC survey
    (Les Ulis : EDP Sciences, 2021) Abril-Melgarejo, Valentina; Epinat, Benoît; Mercier, Wilfried; Contini, Thierry; Boogaard, Leindert A.; Brinchmann, Jarle; Finley, Hayley; Michel-Dansac, Léo; Ventou, Emmy; Amram, Philipe; Krajnović, Davor; Mahler, Guillaume; Pineda, Juan C.B.; Richard, Johan
    Context. Galaxies in dense environments are subject to interactions and mechanisms that directly affect their evolution by lowering their gas fractions and consequently reducing their star-forming capacity earlier than their isolated counterparts. Aims. The aim of our project is to get new insights into the role of environment in the stellar and baryonic content of galaxies using a kinematic approach, through the study of the Tully-Fisher relation (TFR). Methods. We study a sample of galaxies in eight groups, over-dense by a factor larger than 25 with respect to the average projected density, spanning a redshift range of 0.5 < z < 0.8 and located in ten pointings of the MAGIC MUSE Guaranteed Time Observations program. We perform a morpho-kinematics analysis of this sample and set up a selection based on galaxy size, [O » II]λλ3727,3729 emission line doublet signal-to-noise ratio, bulge-to-disk ratio, and nuclear activity to construct a robust kinematic sample of 67 star-forming galaxies. Results. We show that this selection considerably reduces the number of outliers in the TFR, which are predominantly dispersion-dominated galaxies. Similar to other studies, we find that including the velocity dispersion in the velocity budget mainly affects galaxies with low rotation velocities, reduces the scatter in the relation, increases its slope, and decreases its zero-point. Including gas masses is more significant for low-mass galaxies due to a larger gas fraction, and thus decreases the slope and increases the zero-point of the relation. Our results suggest a significant offset of the TFR zero-point between galaxies in low- and high-density environments, regardless of the kinematics estimator used. This can be interpreted as a decrease in either stellar mass by ∼0.05 - 0.3 dex or an increase in rotation velocity by ∼0.02 - 0.06 dex for galaxies in groups, depending on the samples used for comparison. We also studied the stellar and baryon mass fractions within stellar disks and found they both increase with stellar mass, the trend being more pronounced for the stellar component alone. These fractions do not exceed 50%. We show that this evolution of the TFR is consistent either with a decrease in star formation or with a contraction of the mass distribution due to the environment. These two effects probably act together, with their relative contribution depending on the mass regime. © V. Abril-Melgarejo et al. 2021.
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    Distance of Hi-GAL sources
    (Les Ulis : EDP Sciences, 2021) Mège, P.; Russeil, D.; Zavagno, A.; Elia, D.; Molinari, S.; Brunt, C.M.; Butora, R.; Cambresy, L.; Di Giorgio, A.M.; Fenouillet, T.; Fukui, Y.; Lambert, J.C.; Makai, Z.; Merello, M.; Meunier, J.C.; Molinaro, M.; Moreau, C.; Pezzuto, S.; Poulin, Y.; Schisano, E.; Schuller, F.
    Aims. Distances are key to determining the physical properties of sources. In the Galaxy, large (> 10 000) homogeneous samples of sources for which distance are available, covering the whole Galactic distance range, are still missing. Here we present a catalog of velocity and distance for a large sample (> 100 000) of Hi-GAL compact sources. Methods. We developed a fully automatic Python package to extract the velocity and determine the distance. To assign a velocity to a Hi-GAL compact source, the code uses all the available spectroscopic data complemented by a morphological analysis. Once the velocity is determined, if no stellar or maser parallax distance is known, the kinematic distance is calculated and the distance ambiguity (for sources located inside the Solar circle) is solved with the H I self-absorption method or from distance-extinction data. Results. Among the 150 223 compact sources of the Hi-GAL catalog, we obtained a distance for 124 069 sources for the 5σ catalog (and 128 351 sources for the 3σ catalog), where σ represents the noise level of each molecular spectrum used for the line detections made at 5σ and 3σ to produce the respective catalogs. © P. Mège et al. 2021.
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    The flare likelihood and region eruption forecasting (FLARECAST) project: flare forecasting in the big data & machine learning era
    (Les Ulis : EDP Sciences, 2021) Georgoulis, Manolis K.; Bloomfield, D. Shaun; Piana, Michele; Massone, Anna Maria; Soldati, Marco; Gallagher, Peter T.; Pariat, Etienne; Vilmer, Nicole; Buchlin, Eric; Baudin, Frederic; Csillaghy, Andre; Sathiapal, Hanna; Jackson, David R.; Alingery, Pablo; Benvenuto, Federico; Campi, Cristina; Florios, Konstantinos; Gontikakis, Constantinos; Guennou, Chloe; Guerra, Jordan A.; Kontogiannis, Ioannis; Latorre, Vittorio; Murray, Sophie A.; Park, Sung-Hong; Stachelski, Samuel von; Torbica, Aleksandar; Vischi, Dario; Worsfold, Mark
    The European Union funded the FLARECAST project, that ran from January 2015 until February 2018. FLARECAST had a research-to-operations (R2O) focus, and accordingly introduced several innovations into the discipline of solar flare forecasting. FLARECAST innovations were: first, the treatment of hundreds of physical properties viewed as promising flare predictors on equal footing, extending multiple previous works; second, the use of fourteen (14) different machine learning techniques, also on equal footing, to optimize the immense Big Data parameter space created by these many predictors; third, the establishment of a robust, three-pronged communication effort oriented toward policy makers, space-weather stakeholders and the wider public. FLARECAST pledged to make all its data, codes and infrastructure openly available worldwide. The combined use of 170+ properties (a total of 209 predictors are now available) in multiple machine-learning algorithms, some of which were designed exclusively for the project, gave rise to changing sets of best-performing predictors for the forecasting of different flaring levels, at least for major flares. At the same time, FLARECAST reaffirmed the importance of rigorous training and testing practices to avoid overly optimistic pre-operational prediction performance. In addition, the project has (a) tested new and revisited physically intuitive flare predictors and (b) provided meaningful clues toward the transition from flares to eruptive flares, namely, events associated with coronal mass ejections (CMEs). These leads, along with the FLARECAST data, algorithms and infrastructure, could help facilitate integrated space-weather forecasting efforts that take steps to avoid effort duplication. In spite of being one of the most intensive and systematic flare forecasting efforts to-date, FLARECAST has not managed to convincingly lift the barrier of stochasticity in solar flare occurrence and forecasting: solar flare prediction thus remains inherently probabilistic.
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    Ultrafast laser inscription of asymmetric integrated waveguide 3 dB couplers for astronomical K-band interferometry at the CHARA array
    (Washington, DC : Soc., 2021) Benoît, Aurélien; Pike, Fraser A.; Sharma, Tarun K.; MacLachlan, David G.; Dinkelaker, Aline N.; Nayak, Abani S.; Madhav, Kalaga; Roth, Martin M.; Labadie, Lucas; Pedretti, Ettore; Brummelaar, Theo A. ten; Scott, Nic; Coudé du Foresto, Vincent; Thomson, Robert R.
    We present the fabrication and characterization of 3 dB asymmetric directional couplers for the astronomical K-band at wavelengths between 2.0 and 2.4 µm. The couplers were fabricated in commercial Infrasil silica glass using an ultrafast laser operating at 1030 nm. After optimizing the fabrication parameters, the insertion losses of straight single-mode waveguides were measured to be ∼1.2±0.5dB across the full K-band. We investigate the development of asymmetric 3 dB directional couplers by varying the coupler interaction lengths and by varying the width of one of the waveguide cores to detune the propagation constants of the coupled modes. In this manner, we demonstrate that ultrafast laser inscription is capable of fabricating asymmetric 3 dB directional couplers for future applications in K-band stellar interferometry. Finally, we demonstrate that our couplers exhibit an interferometric fringe contrast of >90%. This technology paves the path for the development of a two-telescope K-band integrated optic beam combiner for interferometry to replace the existing beam combiner (MONA) in Jouvence of the Fiber Linked Unit for Recombination (JouFLU) at the Center for High Angular Resolution Astronomy (CHARA) telescope array.