Monthly Notices of the Royal Astronomical Society

Denis-Alpizar,, Otoniel;Rubayo-Soneira,, Jesús

doi: 10.1093/mnras/stz928pmid: N/A

Abstract The recent detections of CF+ and its proposition as a tracer of fluorine and C+ in the interstellar medium (ISM), have increased the interest in this system. For a correct interpretation of physical-chemical conditions of the regions where this molecule is observed, its collisional rate coefficients with the most common colliders of the ISM are required. The main goal of the present work is to study the collision of CF+ with para-H2 (j = 0) and report a large set of rotational rate coefficients for this system. A new averaged potential energy surface (PES) from ab initio energies at the CCSD(T)-F12 /aug-cc-pVTZ level of theory was developed for this work. Close-coupling scattering calculations were performed for the lowest 20 rotational levels of CF+. The rotational rate coefficients from 10 K to 300 K are reported. Discrepancies of these new rates with those estimated from CF++He were found for both magnitude and propensity rules. For CF++para-H2, Δj = −1 have the most significant values, and the rates decrease with the increment of ∣Δj∣. The new data here determined can be useful for modeling the conditions of the ISM where CF+ has been observed. astrochemistry, molecular data, molecular processes, scattering, ISM: molecules This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Drew, J, E;Monguió,, M;Wright, N, J

doi: 10.1093/mnras/stz864pmid: N/A

Abstract The very bright and compact massive young cluster, NGC 3603, has been cited as an example of a starburst in the Milky Way and compared with the much-studied R136/30 Doradus region in the Large Magellanic Cloud. Here we build on the discovery by Mohr-Smith et al. (2017) of a large number of reddened O stars around this cluster. We construct a list of 288 candidate O stars with proper motions, in a region of sky spanning 1.5 × 1.5 square degrees centered on NGC 3603, by cross-matching the Mohr-Smith et al. (2017) catalogue with Gaia DR2 (Gaia Collaboration et al. 2018). This provides the basis for a first comprehensive examination of the proper motions of these massive stars in the halo of NGC 3603, relative to the much better studied central region. We identify up to 11 likely O star ejections – 8 of which would have been ejected between 0.60 and 0.95 Myr ago (supporting the age of ∼1 Myr that has been attributed to the bright cluster centre). Seven candidate ejections are arranged in a partial ring to the south of the cluster core spanning radii of 9–18 arcmin (18–36 pc if the cluster is 7 kpc away). We also show that the cluster has a halo of a further ∼100 O stars extending to a radius of at least 5 arcmin, adding to the picture of NGC 3603 as a scaled down version of the R136/30 Dor region. stars: early-type, (Galaxy:) open clusters and associations: NGC 3603, Galaxy: structure, surveys This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Shaaban, S, M;Lazar,, M;Yoon, P, H;Poedts,, S;López, R, A

doi: 10.1093/mnras/stz830pmid: N/A

Abstract The hot beaming (or strahl) electrons responsible for the main electron heat-flux in the solar wind are believed to be self-regulated by the electromagnetic beaming instabilities, also known as the heat-flux instabilities. Here we report the first quasi-linear theoretical approach of the whistler unstable branch able to characterize the long-term saturation of the instability as well as the relaxation of the electron velocity distributions. The instability saturation is not solely determined by the drift velocities, which undergo only a minor relaxation, but mainly from a concurrent interaction of electrons with whistlers that induces (opposite) temperature anisotropies of the core and beam populations and reduces the effective anisotropy. These results might be able to (i) explain the low intensity of the whistler heat-flux fluctuations in the solar wind (although other explanations remain possible and need further investigation), and (ii) confirm a reduced effectiveness of these fluctuations in the relaxation and isotropization of the electron strahl and in the regulation of the electron heat-flux. instabilities, solar wind, methods: numerical This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Piersanti,, Luciano;Yungelson, Lev, R;Cristallo,, Sergio;Tornambé,, Amedeo

doi: 10.1093/mnras/stz929pmid: N/A

errata, addenda, accretion, binaries: general, supernovae: general, nucleosynthesis This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Bengaly, C A, P;Siewert, T, M;Schwarz, D, J;Maartens,, R

doi: 10.1093/mnras/stz832pmid: N/A

Abstract The dipole anisotropy seen in the cosmic microwave background radiation is interpreted as due to our peculiar motion. The Cosmological Principle implies that this cosmic dipole signal should also be present, with the same direction, in the large-scale distribution of matter. Measurement of the cosmic matter dipole constitutes a key test of the standard cosmological model. Current measurements of this dipole are barely above the expected noise and unable to provide a robust test. Upcoming radio continuum surveys with the SKA should be able to detect the dipole at high signal to noise. We simulate number count maps for SKA survey specifications in Phases 1 and 2, including all relevant effects. Nonlinear effects from local large-scale structure contaminate the cosmic (kinematic) dipole signal, and we find that removal of radio sources at low redshift (z ≲ 0.5) leads to significantly improved constraints. We forecast that the SKA could determine the kinematic dipole direction in Galactic coordinates with an error of (Δl, Δb) ∼ (9°, 5°) to (8°, 4°), depending on the sensitivity. The predicted errors on the relative speed are ∼10%. These measurements would significantly reduce the present uncertainty on the direction of the radio dipole, and thus enable the first critical test of consistency between the matter and CMB dipoles. Cosmology: observations, Cosmology: theory, (cosmology:) large-scale structure of the Universe This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Buck,, Tobias;Dutton, Aaron, A;Macciò, Andrea, V

doi: 10.1093/mnras/stz969pmid: N/A

Abstract State-of-the-art cosmological hydrodynamical simulations of galaxy formation have reached the point at which their outcomes result in galaxies with ever more realism. Still, the employed sub-grid models include several free parameters such as the density threshold, n, to localize the star-forming gas. In this work, we investigate the possibilities to utilize the observed clustered nature of star formation (SF) in order to refine SF prescriptions and constrain the density threshold parameter. To this end, we measure the clustering strength, correlation length and power-law index of the two-point correlation function of young (τ < 50 Myr) stellar particles and compare our results to observations from the HST Legacy Extragalactic UV Survey (LEGUS). Our simulations reveal a clear trend of larger clustering signal and power-law index and lower correlation length as the SF threshold increases with only mild dependence on galaxy properties such as stellar mass or specific star formation rate. In conclusion, we find that the observed clustering of SF is inconsistent with a low threshold for SF (n < 1 cm−3) and strongly favours a high value for the density threshold of SF (n > 10 cm−3), as for example employed in the NIHAO project. cosmology: dark matter, galaxies: formation, galaxies: structure, galaxies: star formation, ISM: structure, methods: N-body simulation This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Beasor, Emma, R;Davies,, Ben;Smith,, Nathan;Bastian,, Nate

doi: 10.1093/mnras/stz732pmid: N/A

Abstract There is growing evidence that star clusters can no longer be considered simple stellar populations (SSPs). Intermediate and old age clusters are often found to have extended main sequence turn-offs (eMSTOs) which are difficult to explain with single age isochrones, an effect attributed to rotation. In this paper, we provide the first characterisation of this effect in young (<20Myr) clusters. We determine ages for 4 young massive clusters (2 LMC, 2 Galactic) by three different methods: using the brightest single turn-off (TO) star; using the luminosity function (LF) of the TO; and by using the lowest Lbol red supergiant (RSG). The age found using the cluster TO is consistently younger than the age found using the lowest RSG Lbol. Under the assumption that the lowest luminosity RSG age is the ‘true’ age, we argue that the eMSTOs of these clusters cannot be explained solely by rotation or unresolved binaries. We speculate that the most luminous stars above the TO are massive blue straggler stars formed via binary interaction, either as mass gainers or merger products. Therefore, using the cluster TO method to infer ages and initial masses of post-main sequence stars such as Wolf-Rayet stars, luminous blue variables and RSGs, will result in ages inferred being too young and masses too high. stars: evolution, galaxies: clusters, stars: massive, blue stragglers This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Paudel, R, R;Gizis, J, E;Mullan, D, J;Schmidt, S, J;Burgasser, A, J;Williams, P K, G;Youngblood,, A;Stassun, K, G

doi: 10.1093/mnras/stz886pmid: N/A

Abstract We observed strong superflares (defined as flares with energy in excess of 1033 erg) on three late-M dwarfs: 2MASS J08315742+2042213 (hereafter 2M0831+2042; M7 V), 2MASS J08371832+2050349 (hereafter 2M0837+2050; M8 V) and 2MASS J08312608+2244586 (hereafter 2M0831+2244; M9 V). 2M0831+2042 and 2M0837+2050 are members of the young (∼700 Myr) open cluster Praesepe. The strong superflare on 2M0831+2042 has an equivalent duration (ED) of 13.7 hr and an estimated energy of 1.3 × 1035 erg. We observed five superflares on 2M0837+2050, on which the strongest superflare has an ED of 46.4 hr and an estimated energy of 3.5 × 1035 erg. This energy is larger by 2.7 orders of magnitude than the largest flare observed on the older (7.6 Gyr) planet-hosting M8 dwarf TRAPPIST-1. Furthermore, we also observed five superflares on 2M0831+2244 which is probably a field star. The estimated energy of the strongest superflare on 2M0831+2244 is 6.1 × 1034 erg. 2M0831+2042, 2M0837+2050 and 2M0831+2244 have rotation periods of 0.556±0.002, 0.193±0.000 and 0.292±0.001 d respectively, which we measured by using K2 light curves. We compare the flares of younger targets with those of TRAPPIST-1 and discuss the possible impacts of such flares on planets in the habitable zone of late-M dwarfs. stars: individual: (2MASS J08371832+2050349 2MASS J08315742+2042213 2MASS J08312608+2244586 TRAPPIST-1), stars: activity, stars: low-mass, stars: flare This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Olech,, M;Szymczak,, M;Wolak,, P;Sarniak,, R;Bartkiewicz,, A

doi: 10.1093/mnras/stz926pmid: N/A

Abstract Discovery of periodic maser emission was an unexpected result from monitoring observations of methanol transitions in high-mass young stellar objects. We report on the detection of five new periodic sources from a monitoring program with the Torun 32 m telescope. Variability with a period of 149 to 540 d and different patterns from sinusoidal-like to intermittent was displayed. Three dimensional structure of G59.633−0.192 determined from the time delays of burst peaks of the spectral features and high angular resolution map implies that the emission traces a disk. For this source the 6.7 GHz light curve followed the infrared variability supporting a radiative scheme of pumping. An unusual time delay of ∼80 d occurred in G30.400−0.296 could not be explained by the light travel time and may suggest a strong differentiation of physical conditions and excitation in this deeply embedded source. Our observations suggest the intermittent variability may present a simple response of maser medium to the underlying variability induced by the accretion luminosity while other variability patterns may reflect more complex changes in the physical conditions. masers, stars:formation, ISM:clouds, radio lines:ISM This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Smith, Robert, E;Angulo, Raul, E

doi: 10.1093/mnras/stz890pmid: N/A

Abstract We use a suite of high-resolution N-body simulations and state-of-the-art perturbation theory to improve the code halofit, which predicts the nonlinear matter power spectrum. We restrict attention to parameters in the vicinity of the Planck Collaboration’s best fit. On large-scales (k≲ 0.07 h Mpc−1), our model evaluates the 2-loop calculation from the Multi-point Propagator Theory of Bernardeau et al. (2012). On smaller scales (k≳ 0.7 h Mpc−1), we transition to a smoothing-spline-fit model, that characterises the differences between the Takahashi et al. (2012) recalibration of halofit2012 and our simulations. We use an additional suite of simulations to explore the response of the power spectrum to variations in the cosmological parameters. In particular, we examine: the time evolution of the dark energy equation of state (w0, wa); the matter density Ωm; the physical densities of CDM and baryons (ωc, ωb); and the primordial power spectrum amplitude As, spectral index ns, and its running α. We construct correction functions, which improve halofit’s dependence on cosmological parameters. Our newly calibrated model reproduces all of our data with ≲ 1% precision. Including various systematic errors, such as choice of N-body code, resolution, and through inspection of the scaled second order derivatives, we estimate the accuracy to be ≲ 3% over the hyper-cube: w0 ∈ { − 1.05, −0.95}, wa ∈ { − 0.4, 0.4}, Ωm, 0 ∈ {0.21, 0.4}, ωc ∈ {0.1, 0.13}, ωb ∈ {2.0, 2.4}, ns ∈ {0.85, 1.05}, As ∈ {1.72 × 10−9, 2.58 × 10−9}, α ∈ { − 0.2, 0.2} up to k = 9.0 h Mpc−1 and out to z = 3. Outside of this range the model reverts to halofit2012. We release all power spectra data with the C-code NGenHalofit at: https://[email protected]/ngenhalofitteam/ngenhalofitpublic.git. Cosmology: large-scale structure of Universe This content is only available as a PDF. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)