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J.P. Magué & B. Ménard

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[1]  arXiv:1606.07431 [pdf, other]
Title: Cluster dynamics largely shapes protoplanetary disc sizes
Comments: Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

It is still on open question to what degree the cluster environment influences the sizes of protoplanetary discs surrounding young stars. Particularly so for the short-lived clusters typical for the solar neighbourhood in which the stellar density and therefore the influence of the cluster environment changes considerably over the first 10 Myr. In previous studies often the effect of the gas on the cluster dynamics has been neglected, this is remedied here. Using the code NBody6++ we study the stellar dynamics in different developmental phases - embedded, expulsion, expansion - including the gas and quantify the effect of fly-bys on the disc size. We concentrate on massive clusters ($M_{\text{cl}} \geq 10^3 - 6 \cdot 10^4 M_{\text{Sun}}$), which are representative for clusters like the Orion Nebula Cluster (ONC) or NGC 6611. We find that not only the stellar density but also the duration of the embedded phase matters. The densest clusters react fastest to the gas expulsion and drop quickly in density, here 98% of relevant encounters happen before gas expulsion. By contrast, discs in sparser clusters are initially less affected but as they expand slower 13% of discs are truncated after gas expulsion. For ONC-like clusters we find that usually discs larger than 500 AU are affected by the environment, which corresponds to the observation that 200 AU-sized discs are common. For NGC 6611-like clusters disc sizes are cut-down on average to roughly 100 AU. A testable hypothesis would be that the discs in the centre of NGC 6611 should be on average ~20 AU and therefore considerably smaller than in the ONC.

[2]  arXiv:1606.07433 [pdf, other]
Title: Deep XMM-Newton Observations of the NW Radio Relic Region of Abell 3667
Comments: 22 pages, 11 figures, submitted to the Astrophysical Journal
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

The results of long XMM-Newton X-ray observations of the NW radio relic of Abell 3667 are presented. A shock is detected at the sharp outer edge of the radio relic, both in the X-ray surface brightness and the temperature profiles. The Mach number is M = 2.54^+0.80_-0.43. The temperature jump at the shock is larger than expected from the density jump, which may indicate that a dynamically important magnetic field aligned primarily parallel to the shock front is present. The gas temperature rises gradually over several arc minutes within the shock region. This could indicate that the shock energy is initially dissipated into some mix of thermal and nonthermal (e.g., turbulence) components, and that the nonthermal energy decays into heat in the post-shock region. The observed radio relic can be powered if ~0.2% of the energy dissipated in the shock goes into the (re)acceleration of relativistic electrons. We show that the observed steepening of the radio spectrum with distance behind the shock is consistent with radiative losses by the radio-emitting electrons. However, the radio spectrum immediately behind the shock is flatter than expected for linear diffusive shock acceleration of thermal electrons. This suggests that the shock re-accelerates a pre-existing population of relativistic electrons. We also detect a bright, cool region (the "Mushroom") to the south of the radio relic, which we propose is the remnant cool core of a merging subcluster, and that this subcluster was the driver for the observed NW shock. In this model, the properties of Abell 3667 are mainly the result of an offset binary merger, and the cluster is being observed about 1 Gyr after first core passage. We predict that deeper X-ray or SZ observations of the SE radio relic will reveal a second merger shock at the outer edge.

[3]  arXiv:1606.07434 [pdf, other]
Title: Cosmological Constraints with Clustering-Based Redshifts
Comments: 7 pages, 3 figures, 2 tables; to be submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We demonstrate that observations lacking reliable redshift information, such as photometric and radio continuum surveys, can produce robust measurements of cosmological parameters when empowered by clustering-based redshift estimation. This method infers the redshift distribution based on the spatial clustering of sources, using cross-correlation with a reference dataset with known redshifts. Applying this method to the existing SDSS photometric galaxies, and projecting to future radio continuum surveys, we show that sources can be efficiently divided into several redshift bins, increasing their ability to constrain cosmological parameters. We forecast constraints on the dark-energy equation-of-state and on local non-gaussianity parameters. We explore several pertinent issues, including the tradeoff between including more sources versus minimizing the overlap between bins, the shot-noise limitations on binning, and the predicted performance of the method at high redshifts. Remarkably, we find that, once this technique is implemented, constraints on dynamical dark energy from the SDSS imaging catalog can be competitive with, or better than, those from the spectroscopic BOSS survey and even future planned experiments. Further, constraints on primordial non-Gaussianity from future large-sky radio-continuum surveys can outperform those from the Planck CMB experiment, and rival those from future spectroscopic galaxy surveys. The application of this method thus holds tremendous promise for cosmology.

[4]  arXiv:1606.07435 [pdf, other]
Title: The Lyman-alpha luminosity function at z=5.7-6.6 and the steep drop of the faint end: implications for reionization
Authors: Sérgio Santos (Lisbon), David Sobral (Lancaster), Jorryt Matthee (Leiden)
Comments: 16 pages, 7 figures. Submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present new results from the widest narrow band survey search for Lyman-alpha (Lya) emitters at z=5.7, just after reionization. We survey a total of 7 deg$^2$ spread over the COSMOS, UDS and SA22 fields. We find over 11,000 line emitters, out of which 514 are robust Lya candidates at z=5.7 within a volume of 6.3x10$^6$ Mpc$^3$. Our Lya emitters span a wide range in Lya luminosities, from faint to bright (L$_{\rm Ly\alpha}\sim10^{42.5-44}$ erg s$^{-1}$) and rest-frame equivalent widths (EW$_0$~25-1000 \AA) in a single, homogeneous data-set. By combining all our fields we find that the faint end slope of the z=5.7 Lya luminosity function is very steep, with $\alpha=-2.3^{+0.4}_{-0.3}$. We also present an updated z=6.6 Lya luminosity function, based on comparable volumes and obtained with the same methods, which we directly compare with that at z=5.7. We find a significant decline of the number density of faint Lya emitters from z=5.7 to z=6.6 (by $0.5\pm0.1$ dex), but no evolution at the bright end/no evolution in L*. Faint Lya emitters at z=6.6 show much more extended haloes than those at z=5.7, suggesting that neutral Hydrogen plays an important role, increasing the scattering and leading to observations missing faint Lya emission within the epoch of reionization. All together, our results indicate that we are observing patchy reionization which happens first around the brightest Lya emitters, allowing the number densities of those sources to remain unaffected by the increase of neutral Hydrogen fraction from z~5 to z~7.

[5]  arXiv:1606.07436 [pdf, other]
Title: Equilibrium model prediction for the scatter in the star-forming main sequence
Comments: 11 pages, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The analytic "equilibrium model" for galaxy evolution using a mass balance equation is able to reproduce mean observed galaxy scaling relations between stellar mass, halo mass, star formation rate (SFR) and metallicity across the majority of cosmic time with a small number of parameters related to feedback. Here we aim to test this data-constrained model to quantify deviations from the mean relation between stellar mass and SFR, i.e. the star-forming galaxy main sequence (MS). We implement fluctuation in halo accretion rates parameterised from merger-based simulations, and quantify the intrinsic scatter introduced into the MS under the assumption that fluctuations in star formation follow baryonic inflow fluctuations. We predict the 1-sigma MS scatter to be ~ 0.2 - 0.25 dex over the stellar mass range 10^8 Mo to 10^11 Mo and a redshift range 0.5 < z < 3 for SFRs averaged over 100 Myr. The scatter increases modestly at z > 3, as well as by averaging over shorter timescales. The contribution from merger-induced star formation is generally small, around 5% today and 10 - 15% during the peak epoch of cosmic star formation. These results are generally consistent with available observations, suggesting that deviations from the MS primarily reflect stochasticity in the inflow rate owing to halo mergers.

[6]  arXiv:1606.07437 [pdf, other]
Title: Orbital eccentricities in primordial black holes binaries
Comments: 13 pages, 8 figures, 3 tables and 1 appendix
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

It was recently suggested that the merger of $\sim30\,M_\odot$ primordial black holes (PBHs) may provide a significant number of events in gravitational-wave observatories over the next decade, if they make up an appreciable fraction of the dark matter. Here we show that measurement of the eccentricities of the inspiralling binary black holes can be used to distinguish these binaries from those produced by more traditional astrophysical mechanisms. These PBH binaries are formed on highly eccentric orbits and can then merge on timescales that in some cases are years or less, retaining some eccentricity in the last seconds before the merger. This is to be contrasted with massive-stellar-binary, globular-cluster, or other astrophysical origins for binary black holes (BBHs) in which the orbits have very effectively circularized by the time the BBH enters the observable LIGO window. Here we discuss the features of the gravitational-wave signals that indicate this eccentricity and forecast the sensitivity of LIGO and the Einstein Telescope to such effects. We show that if PBHs make up the dark matter, then roughly one event should have a detectable eccentricity given LIGO's expected sensitivity and observing time of six years. The Einstein Telescope should see $O(10)$ such events after ten years.

[7]  arXiv:1606.07438 [pdf, ps, other]
Title: Secular dynamics of multiplanet systems: implications for the formation of hot and warm Jupiters via high-eccentricity migration
Comments: Submitted to MNRAS. 14 pages, 10 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Hot Jupiters (HJs) are Jupiter-like planets that reside very closely to their host star, within $\sim 0.1\,\mathrm{AU}$. Their formation is not well understood. It is generally believed that they cannot have formed in situ, implying that some form of migration must have occurred after their initial formation. We study the production of HJs through secular evolution in multiplanet systems with three to five planets. In this variant of high-$e$ migration, the eccentricity of the orbit of the innermost planet is excited on secular time-scales, triggering orbital migration due to tidal dissipation. We use a secular dynamics code and carry out a population synthesis study. We find that HJs are only produced if the viscous time-scale is short ($\approx 0.014$ yr). In contrast, in up to $\approx 0.3$ of systems, the innermost planet is tidally disrupted. The orbital period distribution is peaked around 5 d, consistent with observations. The median HJ mass is $1\,M_\mathrm{J}$ with a maximum of $\approx 2 \, M_\mathrm{J}$, similar to observed HJs. Approximately 0.1 of the HJs have retrograde orbits with respect to the stellar spin. We do not find any warm Jupiters in our simulations, i.e. planets with semimajor axes between 0.1 and 1 AU.

[8]  arXiv:1606.07439 [pdf, other]
Title: A weak lensing view of the downsizing of star-forming galaxies
Comments: Submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We describe a weak lensing view of the downsizing of star forming galaxies based on cross correlating a weak lensing ($\kappa$) map with a predicted map constructed from a redshift survey. Moderately deep and high resolution images with Subaru/Hyper Suprime-Cam covering the 4 deg^2 DLS F2 field provide a $\kappa$ map with 1 arcmin resolution. A dense complete redshift survey of the F2 field including 12,705 galaxies with $R\leq20.6$ is the basis for construction of the predicted map. The zero-lag cross-correlation between the \kappa and predicted maps is significant at the $30\sigma$ level. The width of the cross-correlation peak is comparable with the angular scale of rich cluster at $z\sim0.3$, the median depth of the redshift survey. Slices of the predicted map in $\delta{z} = 0.05$ redshift bins enable exploration of the impact of structure as a function of redshift. The zero-lag normalised cross-correlation has significant local maxima at redshifts coinciding with known massive X-ray clusters. Even in slices where there are no known massive clusters, there is significant signal in the cross-correlation originating from lower mass groups that trace the large-scale of the universe. Spectroscopic $D_n4000$ measurements enable division of the sample into star-forming and quiescent populations. The significance of the cross-correlation with structure containing star-forming galaxies increases with redshift from $5\sigma$ at $z = 0.3$ to $7 \sigma$ at $z = 0.5$. The weak lensing results are consistent with the downsizing view of galaxy evolution established on the basis of many other independent studies.

[9]  arXiv:1606.07442 [pdf, other]
Title: Deep Recurrent Neural Networks for Supernovae Classification
Comments: 6 pages, 3 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Learning (cs.LG); Data Analysis, Statistics and Probability (

We apply deep recurrent neural networks, which are capable of learning complex sequential information, to classify supernovae. The observational time and filter fluxes are used as inputs to the network, but since the inputs are agnostic additional data such as host galaxy information can also be included. Using the Supernovae Photometric Classification Challenge (SPCC) data, we find that deep networks are capable of learning about light curves, however the performance of the network is highly sensitive to the amount of training data. For a training size of 50% of the representational SPCC dataset (around 104 supernovae) we obtain a type Ia vs non type Ia classification accuracy of 94.8%, an area under the Receiver Operating Characteristic curve AUC of 0.986 and a SPCC figure-of-merit F1 = 0.64. We also apply a pre-trained model to obtain classification probabilities as a function of time, and show it can give early indications of supernovae type. Our method is competitive with existing algorithms and has applications for future large-scale photometric surveys.

[10]  arXiv:1606.07443 [pdf, other]
Title: Impact of Cosmic Variance on the Galaxy-Halo Connection for Lyman-$α$ Emitters
Comments: 7 Pages, 5 figures. Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

In this paper we study the impact of cosmic variance and observational uncertainties in constraining the mass and occupation fraction, $f_{\rm occ}$, of dark matter halos hosting Ly-$\alpha$ Emitting Galaxies (LAEs) at high redshift. To this end, we construct mock catalogs from an N-body simulation to match the typical size of observed fields at $z=3.1$ ($\sim 1 {\rm deg^2}$). In our model a dark matter halo with mass in the range $M_{\rm min}<M_{\mathrm h}<M_{\rm max}$ can only host one detectable LAE at most. We proceed to explore the parameter space determined by $M_{\rm min}$,$M_{\rm max}$ and $f_{\rm occ}$ with a Markov Chain Monte-Carlo algorithm using the angular correlation function (ACF) and the LAEs number density as observational constraints. We find that the preferred minimum and maximum masses in our model span a wide range $10^{10.0}h^{-1}{\rm{M_{\odot}}}\leq M_{\rm min} \leq 10^{11.1}h^{-1}{\rm{M_{\odot}}}$ , $10^{11.0}h^{-1}{\rm{M_{\odot}}}\leq M_{\rm max} \leq 10^{13.0}h^{-1}{\rm{M_{\odot}}}$; followed by a wide range in the occupation fraction $0.02\leq f_{\rm occ} \leq 0.30$. As a consequence the median mass, $M_{50}$, of all the consistent models has a large uncertainty $M_{50} = 3.16^{+9.34}_{-2.37}\times 10^{10}$$h^{-1}{\rm{M_{\odot}}}$. However, we find that the same individual models have a relatively tight $1\sigma$ scatter around the median mass $\Delta M_{1\sigma} = 0.55^{+0.11}_{-0.31}$ dex. We are also able to show that \focc\ is uniquely determined by $M_{\rm min}$, regardless of $M_{\rm max}$. We argue that upcoming large surveys covering at least $25$ deg$^{2}$ should be able to put tighter constraints on $M_{\rm min}$ and $f_{\rm occ}$ through the LAE number density distribution width constructed over several fields of $\sim 1$ deg$^{2}$.

[11]  arXiv:1606.07445 [pdf, other]
Title: Nucleosynthesis in AGB stars traced by isotopic ratios. I - Determining the stellar initial mass by means of the $^{17}$O/$^{18}$O ratio
Comments: Submitted to A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The aim of this paper is to investigate the $^{17}$O/$^{18}$O ratio for a sample of AGB stars, containing M-, S- and C-type stars. These ratios are evaluated in relation to fundamental stellar evolution parameters: the stellar initial mass and pulsation period. This study is the first to explore these oxygen ratios for a sample covering the three spectral types. Circumstellar $^{13}$C$^{16}$O, $^{12}$C$^{17}$O and $^{12}$C$^{18}$O line observations were obtained for a sample of nine stars with various single-dish long-wavelength facilities. These data have been fully reduced and analyzed. The line intensity ratios obtained from these observations are then related directly to the surface $^{17}$O/$^{18}$O abundance ratio. Stellar evolution models predict the $^{17}$O/$^{18}$O ratio to be a sensitive function of initial mass and to remain constant throughout the entire TP-AGB phase for stars less massive than 5 M$_{\odot}$. This allows the measured ratio to function as an effective method of determining the initial stellar mass. Observed $^{17}$O/$^{18}$O ratios are found to be well in the range predicted by stellar evolution models. From this, accurate initial mass estimates are calculated for all nine sources. Finally, hints at a possible separation between M/S- and C-type stars when comparing the $^{17}$O/$^{18}$O ratio to the stellar pulsation period are presented.

[12]  arXiv:1606.07446 [pdf, other]
Title: The Nature of Active Galactic Nuclei with Velocity Offset Emission Lines
Comments: 14 pages, 12 figures, accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We obtained Keck/OSIRIS near-IR adaptive optics-assisted integral-field spectroscopy to probe the morphology and kinematics of the ionized gas in four velocity-offset active galactic nuclei (AGNs) from the Sloan Digital Sky Survey. These objects possess optical emission lines that are offset in velocity from systemic as measured from stellar absorption features. At a resolution of ~0.18", OSIRIS allows us to distinguish which velocity offset emission lines are produced by the motion of an AGN in a dual supermassive black hole system, and which are produced by outflows or other kinematic structures. In three galaxies, J1018+2941, J1055+1520 and J1346+5228, the spectral offset of the emission lines is caused by AGN-driven outflows. In the remaining galaxy, J1117+6140, a counterrotating nuclear disk is observed that contains the peak of Pa$\alpha$ emission 0.2" from the center of the galaxy. The most plausible explanation for the origin of this spatially and kinematically offset peak is that it is a region of enhanced Pa$\alpha$ emission located at the intersection zone between the nuclear disk and the bar of the galaxy. In all four objects, the peak of ionized gas emission is not spatially coincident with the center of the galaxy as traced by the peak of the near-IR continuum emission. The peaks of ionized gas emission are spatially offset from the galaxy centers by 0.1"-0.4" (0.1-0.7 kpc). We find that the velocity offset originates at the location of this peak of emission, and the value of the offset can be directly measured in the velocity maps. The emission-line ratios of these four velocity-offset AGNs can be reproduced only with a mixture of shocks and AGN photoionization. Shocks provide a natural explanation for the origin of the spatially and spectrally offset peaks of ionized gas emission in these galaxies.

[13]  arXiv:1606.07447 [pdf, other]
Title: Blazar flares powered by plasmoids in relativistic reconnection
Comments: 20 pages, 13 figures, submitted to MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Powerful flares from blazars with short ($\sim$ min) variability timescales are challenging for current models of blazar emission. Here, we present a physically motivated ab initio model for blazar flares based on the results of recent particle-in-cell (PIC) simulations of relativistic magnetic reconnection. PIC simulations demonstrate that quasi-spherical plasmoids filled with high-energy particles and magnetic fields are a self-consistent by-product of the reconnection process. By coupling our PIC-based results (i.e., plasmoid growth, acceleration profile, particle and magnetic content) with a kinetic equation for the evolution of the electron distribution function we demonstrate that relativistic reconnection in blazar jets can produce powerful flares whose temporal and spectral properties are consistent with the observations. In particular, our model predicts correlated synchrotron and synchrotron self-Compton flares of duration of several hours--days powered by the largest and slowest moving plasmoids that form in the reconnection layer. Smaller and faster plasmoids produce flares of sub-hour duration with higher peak luminosities than those powered by the largest plasmoids. Yet, the observed fluence in both types of flares is similar. Multiple flares with a range of flux-doubling timescales (minutes to several hours) observed over a longer period of flaring activity (days or longer) may be used as a probe of the reconnection layer's orientation and the jet's magnetization. Our model shows that blazar flares are naturally expected as a result of magnetic reconnection in a magnetically-dominated jet.

[14]  arXiv:1606.07448 [pdf, ps, other]
Title: IMF shape constraints from stellar populations and dynamics from CALIFA
Comments: 6 pages, 3 figures, accepted for publication in MNRAS Letters
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In this letter we describe how we use stellar dynamics information to constrain the shape of the stellar IMF in a sample of 27 early-type galaxies from the CALIFA survey. We obtain dynamical and stellar mass-to-light ratios, $\Upsilon_\mathrm{dyn}$ and $\Upsilon_{\ast}$, over a homogenous aperture of 0.5~$R_{e}$. We use the constraint $\Upsilon_\mathrm{dyn} \ge \Upsilon_{\ast}$ to test two IMF shapes within the framework of the extended MILES stellar population models. We rule out a single power law IMF shape for 75% of the galaxies in our sample. Conversely, we find that a double power law IMF shape with a varying high-mass end slope is compatible (within 1$\sigma$) with 95% of the galaxies. We also show that dynamical and stellar IMF mismatch factors give consistent results for the systematic variation of the IMF in these galaxies.

[15]  arXiv:1606.07450 [pdf, other]
Title: Ultra-deep Ks-band Imaging of the Hubble Frontier Fields
Comments: Submitted to ApJS, includes revisions after the first referee report. Reduced mosaics of all six survey fields are provided via the ESO Phase 3 query form at this http URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present an overview of the "KIFF" project, which provides ultra-deep Ks-band imaging of all six of the Hubble Frontier Fields clusters Abell 2744, MACS-0416, Abell S1063, Abell 370, MACS-0717 and MACS-1149. All of these fields have recently been observed with large allocations of Directors' Discretionary Time with the HST and Spitzer telescopes covering 0.4 < lambda < 1.6 microns and 3.6--4.5 microns, respectively. VLT/HAWK-I integrations of the first four fields reach 5-sigma limiting depths of Ks~26.0 (AB, point sources) and have excellent image quality (FWHM ~ 0."4). Shorter Keck/MOSFIRE integrations of the MACS-0717 (MACS-1149) field better observable in the north reach limiting depths Ks=25.5 (25.1) with seeing FWHM ~0."4 (0."5). In all cases the Ks-band mosaics cover the primary cluster and parallel HST/ACS+WFC3 fields. The total area of the Ks-band coverage is 490 arcmin^2. The Ks-band at 2.2 microns crucially fills the gap between the reddest HST filter (1.6 micron ~ H-band) and the IRAC 3.6 micron passband. While reaching the full depths of the space-based imaging is not currently feasible from the ground, the deep Ks-band images provide important constraints on both the redshifts and the stellar population properties of galaxies extending well below the characteristic stellar mass across most of the age of the universe, down to, and including, the redshifts of the targeted galaxy clusters (z < 0.5).

[16]  arXiv:1606.07452 [pdf, ps, other]
Title: Early Quenching of Massive Protocluster Galaxies Around z=2.2 Radio Galaxies
Comments: 9 pages; 9 figures; 2 tables; Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Radio galaxies are among the most massive galaxies in the high redshift universe and are known to often lie in protocluster environments. We have studied the fields of seven z = 2.2 radio galaxies with HAWK-I narrow-band and broad-band imaging in order to map out their environment using Halpha emitters (HAEs). The results are compared to the blank field HAE survey HiZELS. All of the radio galaxy fields are overdense in HAEs relative to a typical HiZELS field of the same area and four of the seven are richer than all except one of 65 essentially random HiZELS subfields of the same size. The star formation rates of the massive HAEs are lower than those necessary to have formed their stellar population in the preceding Gyr - indicating that these galaxies are likely to have formed the bulk of their stars at higher redshifts, and are starting to quench.

[17]  arXiv:1606.07456 [pdf]
Title: The Rapid Transient Surveyor
Comments: 15 pages, 10 figures, 3 tables
Journal-ref: Proc. SPIE 9909, Adaptive Optics Systems V, 9909-15 (2016)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The Rapid Transient Surveyor (RTS) is a proposed rapid-response, high-cadence adaptive optics (AO) facility for the UH 2.2-m telescope on Maunakea. RTS will uniquely address the need for high-acuity and sensitive near-infrared spectral follow-up observations of tens of thousands of objects in mere months by combining an excellent observing site, unmatched robotic observational efficiency, and an AO system that significantly increases both sensitivity and spatial resolving power. We will initially use RTS to obtain the infrared spectra of ~4,000 Type Ia supernovae identified by the Asteroid Terrestrial-Impact Last Alert System over a two year period that will be crucial to precisely measuring distances and mapping the distribution of dark matter in the z < 0.1 universe. RTS will comprise an upgraded version of the Robo-AO laser AO system and will respond quickly to target-of-opportunity events, minimizing the time between discovery and characterization. RTS will acquire simultaneous-multicolor images with an acuity of 0.07-0.10" across the entire visible spectrum (20% i'-band Strehl in median conditions) and <0.16" in the near infrared, and will detect companions at 0.5" at contrast ratio of ~500. The system will include a high-efficiency prism integral field unit spectrograph: R = 70-140 over a total bandpass of 840-1830 nm with an 8.7" by 6.0" field of view (0.15" spaxels). The AO correction boosts the infrared point-source sensitivity of the spectrograph against the sky background by a factor of seven for faint targets, giving the UH 2.2-m the H-band sensitivity of a 5.7-m telescope without AO.

[18]  arXiv:1606.07473 [pdf, other]
Title: Hydrogen Epoch of Reionization Array (HERA)
Comments: 26 pages, 24 figures, 2 tables
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The Hydrogen Epoch of Reionization Array (HERA) is a staged experiment to measure 21 cm emission from the primordial intergalactic medium (IGM) throughout cosmic reionization ($z=6-12$), and to explore earlier epochs of our Cosmic Dawn ($z\sim30$). During these epochs, early stars and black holes heated and ionized the IGM, introducing fluctuations in 21 cm emission. HERA is designed to characterize the evolution of the 21 cm power spectrum to constrain the timing and morphology of reionization, the properties of the first galaxies, the evolution of large-scale structure, and the early sources of heating. The full HERA instrument will be a 350-element interferometer in South Africa consisting of 14-m parabolic dishes observing from 50 to 250 MHz. Currently, 19 dishes have been deployed on site and the next 18 are under construction. HERA has been designated as an SKA Precursor instrument.
In this paper, we summarize HERA's scientific context and provide forecasts for its key science results. After reviewing the current state of the art in foreground mitigation, we use the delay-spectrum technique to motivate high-level performance requirements for the HERA instrument. Next, we present the HERA instrument design, along with the subsystem specifications that ensure that HERA meets its performance requirements. Finally, we summarize the schedule and status of the project. We conclude by suggesting that, given the realities of foreground contamination, current-generation 21 cm instruments are approaching their sensitivity limits. HERA is designed to bring both the sensitivity and the precision to deliver its primary science on the basis of proven foreground filtering techniques, while developing new subtraction techniques to unlock new capabilities. The result will be a major step toward realizing the widely recognized scientific potential of 21 cm cosmology.

[19]  arXiv:1606.07483 [pdf, other]
Title: Discovery of the Interstellar Chiral Molecule Propylene Oxide (CH$_3$CHCH$_2$O)
Journal-ref: Science 2016, 352, 1449
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Life on Earth relies on chiral molecules, that is, species not superimposable on their mirror images. This manifests itself in the selection of a single molecular handedness, or homochirality, across the biosphere. We present the astronomical detection of a chiral molecule, propylene oxide (CH$_3$CHCH$_2$O), in absorption toward the Galactic Center. Propylene oxide is detected in the gas phase in a cold, extended molecular shell around the embedded, massive protostellar clusters in the Sagittarius B2 star-forming region. This material is representative of the earliest stage of solar system evolution in which a chiral molecule has been found.

[20]  arXiv:1606.07484 [pdf, other]
Title: Evolution Of Massive Black Hole Binaries In Rotating Stellar Nuclei: Implications For Gravitational Wave Detection
Comments: 20 pages, 9 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We compute the isotropic gravitational wave (GW) background produced by binary supermassive black holes (SBHs) in galactic nuclei. In our model, massive binaries evolve at early times via gravitational-slingshot interaction with nearby stars, and at later times by the emission of GWs. Our expressions for the rate of binary hardening in the "stellar" regime are taken from the recent work of Vasiliev et al., who show that in the non-axisymmetric galaxies expected to form via mergers, stars are supplied to the center at high enough rates to ensure binary coalescence on Gyr timescales. We also include, for the first time, the extra degrees of freedom associated with evolution of the binary's orbital plane; in rotating nuclei, interaction with stars causes the orientation and the eccentricity of a massive binary to change in tandem, leading in some cases to very high eccentricities (e>0.9) before the binary enters the GW-dominated regime. We argue that previous studies have over-estimated the mean ratio of SBH mass to galaxy bulge mass by factors of 2 - 3. In the frequency regime currently accessible to pulsar timing arrays (PTAs), our assumptions imply a factor 2 - 3 reduction in the characteristic strain compared with the values computed in most recent studies, removing the tension that currently exists between model predictions and the non-detection of GWs.

[21]  arXiv:1606.07510 [pdf]
Title: Orbital solution and evolutionary state for the eclipsing binary 1SWASP J080150.03+471433.8
Comments: 14 pages, 7 figures and 5 tables
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present an orbital solution study for the newly discovered system 1SWASP J080150.03+471433.8 by means of new CCD observations in VRI bands. Our observations were carried out on 25 Feb. 2013 using the Kottamia optical telescope at NRIAG, Egypt. 12 new times of minima were estimated and the observed light curves were analysed using the Wilson-Devinney code. The accepted orbital solution reveals that the primary component of is more massive and hotter than the secondary one by about 280K. The system is an over-contact one with fillout ratio ~ 29% and is located at a distance of 195 Pc. The evolutionary status of the system is investigated by means of stellar models and empirical data.

[22]  arXiv:1606.07539 [pdf]
Title: A Unified Framework for Producing CAI Melting, Wark-Lovering Rims and Bowl-Shaped CAIs
Comments: 70 pages, 41 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Calcium Aluminium Inclusions (CAIs) formed in the Solar System, some 4,567 million years ago. CAIs are almost always surrounded by Wark-Lovering Rims (WLRs), which are a sequence of thin, mono/bi-mineralic layers of refractory minerals, with a total thickness in the range of 1 to 100 microns. Recently, some CAIs have been found that have tektite-like bowl-shapes. To form such shapes, the CAI must have travelled through a rarefied gas at hypersonic speeds. We show how CAIs may have been ejected from the inner solar accretion disc via the centrifugal interaction between the solar magnetosphere and the inner disc rim. They subsequently punched through the hot, inner disc rim wall at hypersonic speeds. This re-entry heating partially or completely evaporated the CAIs. Such evaporation could have significantly increased the metal abundances of the inner disc rim. High speed movement through the inner disc produced WLRs. To match the observed thickness of WLRs required metal abundances at the inner disc wall that are of order ten times that of standard solar abundances. The CAIs cooled as they moved away from the protosun, the deduced CAI cooling rates are consistent with the CAI cooling rates obtained from experiment and observation. The speeds and gas densities required to form bowl-shaped CAIs are also consistent with the expected speeds and gas densities for larger, ~ 1 cm, CAIs punching through an inner accretion disc wall.

[23]  arXiv:1606.07546 [pdf, ps, other]
Title: The Spin-Orbit Evolution of GJ 667C System: The Effect of Composition and Other Planet's Perturbations
Comments: 15 pages, 9 figures, 4 tables. Submited to MNRAS - V3
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Potentially habitable planets within the habitable zone of M-dwarfs are affected by tidal interaction. We studied the tidal evolution in GJ 667C using a numerical code we call TIDEV. We reviewed the problem of the dynamical evolution focusing on the effects that a rheological treatment, different compositions and the inclusion of orbital perturbations, have on the spin-down time and the probability to be trapped in a low spin-orbit resonance. Composition have a strong effect on the spin-down time, changing, in some cases, by almost a factor of 2 with respect to the value estimated for a reference Earth-like model. We calculated the time to reach a low resonance value (3:2) for the configuration of 6 planets. Capture probabilities are affected when assuming different compositions and eccentricities variations. We chose planets b and c to evaluate the probabilities of capture in resonances below 5:2 for two compositions: Earth-like and Waterworld planets. We found that perturbations, although having a secular effect on eccentricities, have a low impact on capture probabilities and noth- ing on spin-down times. The implications of the eccentricity variations and actual habitability of the GJ 667C system are discussed.

[24]  arXiv:1606.07571 [pdf, ps, other]
Title: Detection of Prominent Stellar Disks in the Progenitors of Present-day Massive Elliptical Galaxies
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Massive galaxies at higher redshifts ($\emph{z}$ $>$ 2) show different characteristics from their local counterparts: They are compact and most likely have a disk. In this study, we trace the evolution of local massive galaxies by performing a detailed morphological analysis, namely, fitting single S\'{e}rsic profiles and performing bulge+disk decompositions. We analyze $\sim$ 250 massive galaxies selected from all CANDELS fields (COSMOS, UDS, EGS, GOODS-South and GOODS-North). We confirm that both star-forming and quiescent galaxies increase their sizes significantly from $\emph{z}$ $\approx$ 2.5 to the present day. The global S\'{e}rsic index of quiescent galaxies increases over time (from $n$ $\approx$ 2.5 to $n$ $>$ 4), while that of star-forming galaxies remains roughly constant ($n$ $\approx$ 2.5). By decomposing galaxy profiles into bulge+disk components, we find that massive galaxies at high redshift have prominent stellar disks, which are also evident from visual inspection of the images. By $z$ $\approx$ 0.5, the majority of the disks disappear and massive quiescent galaxies begin to resemble the local elliptical galaxies. Star-forming galaxies have lower bulge-to-total ratios ($B/T$) than their quiescent counterparts at each redshift bin. The bulges of star-forming and quiescent galaxies follow different evolutionary histories, while their disks evolve similarly. We conclude that major mergers, along with minor mergers, have played a crucial role in the significant size increase of high-\emph{z} galaxies and the destruction of their massive and large-scale disks.

[25]  arXiv:1606.07599 [pdf, other]
Title: Evidence of magnetic field decay in massive main-sequence stars
Comments: Accepted for publication on A&A; 9 pages, 8 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

A significant fraction of massive main-sequence stars show strong, large-scale magnetic fields. The origin of these fields, their lifetimes, and their role in shaping the characteristics and evolution of massive stars are currently not well understood. We compile a catalogue of 389 massive main-sequence stars, 61 of which are magnetic, and derive their fundamental parameters and ages. The two samples contain stars brighter than magnitude 9 in the V band and range in mass between 5 and 100 Msun. We find that the fractional main-sequence age distribution of all considered stars follows what is expected for a magnitude limited sample, while that of magnetic stars shows a clear decrease towards the end of the main sequence. This dearth of old magnetic stars is independent of the choice of adopted stellar evolution tracks, and appears to become more prominent when considering only the most massive stars. We show that the decreasing trend in the distribution is significantly stronger than expected from magnetic flux conservation. We also find that binary rejuvenation and magnetic suppression of core convection are unlikely to be responsible for the observed lack of older magnetic massive stars, and conclude that its most probable cause is the decay of the magnetic field, over a time span longer than the stellar lifetime for the lowest considered masses, and shorter for the highest masses. We then investigate the spin-down ages of the slowly rotating magnetic massive stars and find them to exceed the stellar ages by far in many cases. The high fraction of very slowly rotating magnetic stars thus provides an independent argument for a decay of the magnetic fields.

[26]  arXiv:1606.07631 [pdf, other]
Title: PBH Dark Matter in Supergravity Inflation Models
Comments: 8 pages, 3 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We propose a novel scenario to produce abundant primordial black holes (PBHs) in new inflation which is a second phase of a double inflation in the supergravity frame work. In our model, some preinflation phase before the new inflation is assumed and it would be responsible for the primordial curvature perturbations on the cosmic microwave background scale, while the new inflation produces only the small scale perturbations. Our new inflation model has linear, quadratic, and cubic terms in its potential and PBH production corresponds with its flat inflection point. The linear term can be interpreted to come from a supersymmetry-breaking sector, and with this assumption, the vanishing cosmological constant condition after inflation and the flatness condition for the inflection point can be consistently satisfied.

[27]  arXiv:1606.07642 [pdf, ps, other]
Title: IDA: A new software tool for INTEGRAL field spectroscopy Data Analysis
Comments: 7 pages, 6 figures. Presented by B.Garcia Lorenzo at "Galaxies: the Third Dimension", 3-7 December 2001, Cozumel, Mexico
Journal-ref: Galaxies: The Third Dimension, ASP Conference Proceedings, Vol. 282. Edited by Margarita Rosado, Luc Binette, and Lorena Arias. ISBN: 1-58381-125-7. San Francisco: Astronomical Society of the Pacific, 2002., p.501
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA)

We present a software package, IDA, which can easily handle two-dimensional spectroscopy data. IDA has been written in IDL and offers a window-based interface. The available tools can visualize a recovered image from spectra at any desired wavelength interval, obtain velocity fields, velocity dispersion distributions, etc.

[28]  arXiv:1606.07645 [pdf, other]
Title: Cloud Structure of Galactic OB Cluster Forming Regions from Combining Ground and Space Based Bolometric Observations
Comments: ApJ accepted
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We have developed an iterative procedure to systematically combine the millimeter and submillimeter images of OB cluster-forming molecular clouds, which were taken by ground based (CSO, JCMT, APEX, IRAM-30m) and space telescopes (Herschel, Planck). For the seven luminous ($L$$>$10$^{6}$ $L_{\odot}$) Galactic OB cluster-forming molecular clouds selected for our analyses, namely W49A, W43-Main, W43-South, W33, G10.6-0.4, G10.2-0.3, G10.3-0.1, we have performed single-component, modified black-body fits to each pixel of the combined (sub)millimeter images, and the Herschel PACS and SPIRE images at shorter wavelengths. The $\sim$10$"$ resolution dust column density and temperature maps of these sources revealed dramatically different morphologies, indicating very different modes of OB cluster-formation, or parent molecular cloud structures in different evolutionary stages. The molecular clouds W49A, W33, and G10.6-0.4 show centrally concentrated massive molecular clumps that are connected with approximately radially orientated molecular gas filaments. The W43-Main and W43-South molecular cloud complexes, which are located at the intersection of the Galactic near 3-kpc (or Scutum) arm and the Galactic bar, show a widely scattered distribution of dense molecular clumps/cores over the observed $\sim$10 pc spatial scale. The relatively evolved sources G10.2-0.3 and G10.3-0.1 appear to be affected by stellar feedback, and show a complicated cloud morphology embedded with abundant dense molecular clumps/cores. We find that with the high angular resolution we achieved, our visual classification of cloud morphology can be linked to the systematically derived statistical quantities (i.e., the enclosed mass profile, the column density probability distribution function, the two-point correlation function of column density, and the probability distribution function of clump/core separations).

[29]  arXiv:1606.07673 [pdf, other]
Title: Pseudoscalar - sterile neutrino interactions: reconciling the cosmos with neutrino oscillations
Comments: 17 pages, 7 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

The Short BaseLine (SBL) neutrino oscillation anomalies hint at the presence of a sterile neutrino with a mass of around 1 eV. However, such a neutrino is incompatible with cosmological data, in particular observations of the Cosmic Microwave Background (CMB) anisotropies. However, this conclusion can change by invoking new physics. One possibility is to introduce a secret interaction in the sterile neutrino sector mediated by a light pseudoscalar. In this pseudoscalar model, CMB data prefer a sterile neutrino mass that is fully compatible with the mass ranges suggested by SBL anomalies. In addition, this model predicts a value of the Hubble parameter which is completely consistent with local measurements.

[30]  arXiv:1606.07693 [pdf, other]
Title: Cosmic ray interactions in the solar system: The Gerasimova-Zatsepin effect
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Experiment (hep-ex)

The Gerasimova-Zatsepin effect of collisions of ultra-high-energy cosmic ray nuclei with photons emitted by the sun may cause two simultaneous air showers on Earth. This effect is simulated using the full energy spectrum of solar photons, ray tracing through the interplanetary magnetic field and upper limit values for the iron and oxygen cosmic ray fluxes. Only the most abundant interactions in which a single proton is emitted from the nucleus are considered. For the first time the distributions of distances between the individual showers at Earth as a function of the distance of the primary cosmic ray to the Sun are shown. These distributions are used to estimate the capabilities of current detector arrays to measure the Gerasimova-Zatsepin effect and to show that a dedicated array is capable of measuring this effect.

[31]  arXiv:1606.07718 [pdf, ps, other]
Title: Fading Coronal Structure and the Onset of Turbulence in the Young Solar Wind
Authors: C. E. DeForest (SwRI), W. H. Matthaeus (U. Delaware), N. M. Viall (NASA/GSFC), S. R. Cranmer (CU Boulder)
Comments: Accepted for publication in the Astrophysical Journal. 16 pages (emulateapj style), 13 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Above the top of the solar corona, the young slow solar wind transitions from low-beta, magnetically structured flow dominated by radial structures, to high-beta, less structured flow dominated by hydrodynamics. This transition, long inferred via theory, is readily apparent in the sky region close to 10 degrees from the Sun, in processed, background-subtracted solar wind images. We present image sequences collected by the STEREO/HI1 instrument in 2008 Dec, covering apparent distances from approximately 4 to 24 degrees from the center of the Sun and spanning this transition in large-scale morphology of the wind. We describe the observation and novel techniques to extract evolving image structure from the images, and we use those data and techniques to present and quantify the clear textural shift in the apparent structure of the corona and solar wind in this altitude range. We demonstrate that the change in apparent texture is due both to anomalous fading of the radial striae that characterize the corona, and to anomalous relative brightening of locally dense puffs of solar wind that we term "flocculae;" and show that these phenomena are inconsistent with smooth radial flow, but consistent with onset of hydrodynamic or MHD instabilities leading to a turbulent cascade in the young solar wind.

[32]  arXiv:1606.07721 [pdf, other]
Title: Mapping the kinetic Sunyaev-Zel'dovich effect toward MACS J0717.5+3745 with NIKA
Comments: 18 pages, 9 figures, submitted to A&A
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Measurement of the gas velocity distribution in galaxy clusters provides insight into the physics of mergers, through which large scale structures form in the Universe. Velocity estimates within the intracluster medium (ICM) can be obtained via the Sunyaev-Zel'dovich (SZ) effect, but its observation is challenging both in term of sensitivity requirement and control of systematic effects, including the removal of contaminants. In this paper we report resolved observations, at 150 and 260 GHz, of the SZ effect toward the triple merger MACS J0717.5+3745 (z=0.55), using data obtained with the NIKA camera at the IRAM 30m telescope. Assuming that the SZ signal is the sum of a thermal (tSZ) and a kinetic (kSZ) component and by combining the two NIKA bands, we extract for the first time a resolved map of the kSZ signal in a cluster. The kSZ signal is dominated by a dipolar structure that peaks at -5.1 and +3.4 sigma, corresponding to two subclusters moving respectively away and toward us and coincident with the cold dense X-ray core and a hot region undergoing a major merging event. We model the gas electron density and line-of-sight velocity of MACS J0717.5+3745 as four subclusters. Combining NIKA data with X-ray observations from XMM-Newton and Chandra, we fit this model to constrain the gas line-of-sight velocity of each component, and we also derive, for the first time, a velocity map from kSZ data (i.e. that is model-dependent). Our results are consistent with previous constraints on the merger velocities, and thanks to the high angular resolution of our data, we are able to resolve the structure of the gas velocity. Finally, we investigate possible contamination and systematic effects with a special care given to radio and submillimeter galaxies. Among the sources that we detect with NIKA, we find one which is likely to be a high redshift lensed submillimeter galaxy.

[33]  arXiv:1606.07725 [pdf, ps, other]
Title: Prospects for constraining the spin of the massive black hole at the Galactic center via the relativistic motion of a surrounding star
Comments: 10 pages, 7 figures, accepted for publication in the Astrophysical Journal
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

In this paper, we investigate the quality of constraining the spin of the massive black hole (MBH) at the Galactic center (GC), by using full general relativistic simulations of the motion of a surrounding star. We obtain the mapping of the dependence of the spin-induced signals on any spin direction of the MBH for given example stars, which indicates the feasibility to test whether the spin direction is the same as the normal of the young stellar disk located at the GC and further to provide insights into the assembly history of the MBH. We demonstrate the quality of constraining the MBH spin that may be achieved, given any set of the astrometric and the redshift precisions of observational facilities. We find that in the ranges of the astrometric and the velocity precisions with 1--30$\mu$as and 0.1--10 km/s, an improvement in astrometric precision would be more effective in improving the quality of constraining the spin than an improvement in velocity precision. We obtain the parameter space of the semimajor axis and the eccentricity for the orbit of the target star that a high-precision constraint on the GC MBH spin can be obtained via the motion of the star. Our results show that the spin of the GC MBH can be constrained with 1-sigma error <~0.1 or even >~0.02 by monitoring the orbital motion of a star, if existing as expected, with semimajor axis <~300AU and eccentricity >~0.95 over a period shorter than a decade through future facilities.

[34]  arXiv:1606.07741 [pdf, other]
Title: The Hanle and Zeeman polarization signals of the solar Ca II 8542 Å\ line
Comments: 11 pages, 5 figures, accepted for publication in The Astrophysical Journal Letters
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We highlight the main results of a three-dimensional (3D) multilevel radiative transfer investigation about the solar disk-center polarization of the Ca {\sc ii} 8542 \AA\ line. First, we investigate the linear polarization due to the atomic level polarization produced by the absorption and scattering of anisotropic radiation in a 3D model of the solar atmosphere, taking into account the symmetry breaking effects caused by its thermal, dynamic and magnetic structure. Second, we study the contribution of the Zeeman effect to the linear and circular polarization. Finally, we show examples of the Stokes profiles produced by the joint action of atomic level polarization and the Hanle and Zeeman effects. We find that the Zeeman effect tends to dominate the linear polarization signals only in the localized patches of opposite magnetic polarity where the magnetic field is relatively strong and slightly inclined, while outside such very localized patches the linear polarization is often dominated by the contribution of atomic level polarization. We demonstrate that a correct modeling of this last contribution requires taking into account the symmetry breaking effects caused by the thermal, dynamic and magnetic structure of the solar atmosphere, and that in the 3D model used the Hanle effect in forward-scattering geometry (disk center observation) mainly reduces the polarization corresponding to the zero-field case. We emphasize that, in general, a reliable modeling of the linear polarization in the Ca {\sc ii} 8542 \AA\ line requires taking into account the joint action of atomic level polarization and the Hanle and Zeeman effects.

[35]  arXiv:1606.07743 [pdf, other]
Title: Orbital stability of coplanar two-planet exosystems with high eccentricities
Comments: Accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The long-term stability of the evolution of two-planet systems is considered by using the general three body problem (GTBP). Our study is focused on the stability of systems with adjacent orbits when at least one of them is highly eccentric. In these cases, in order for close encounters, which destabilize the planetary systems, to be avoided, phase protection mechanisms should be considered. Additionally, since the GTBP is a non-integrable system, chaos may also cause the destabilization of the system after a long time interval. By computing dynamical maps, based on Fast Lyapunov Indicator, we reveal regions in phase space with stable orbits even for very high eccentricities (e>0.5). Such regions are present in mean motion resonances (MMR). We can determine the position of the exact MMR through the computation of families of periodic orbits in a rotating frame. Elliptic periodic orbits are associated with the presence of apsidal corotation resonances (ACR). When such solutions are stable, they are associated with neighbouring domains of initial conditions that provide long-term stability. We apply our methodology so that the evolution of planetary systems of highly eccentric orbits is assigned to the existence of such stable domains. Particularly, we study the orbital evolution of the extrasolar systems HD 82943, HD 3651, HD 7449, HD 89744 and HD 102272 and discuss the consistency between the orbital elements provided by the observations and the dynamical stability.

[36]  arXiv:1606.07745 [pdf, ps, other]
Title: Interstellar Gas and X-rays toward the Young Supernova Remnant RCW 86; Pursuit to the Origin of the Thermal and Non-thermal X-ray
Comments: 19 pages, 15 figures, 3 tables, submitted to The Journal of High Energy Astrophysics (JHEAp)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

We have analyzed the atomic and molecular gas using the 21 cm HI and 2.6/1.3 mm CO emissions toward the TeV $\gamma$-ray supernova remnant (SNR) RCW 86 in order to identify the interstellar medium interacting with the shock waves of the SNR. We have found intensity depression in HI at a velocity range of $-46$-$-28$ km s$^{-1}$ toward the SNR, suggesting a cavity of the interstellar medium. The HI cavity corresponds with the X-ray shell consisting of thermal and non-thermal emission. The thermal X-rays are coincident with the edge of the HI distribution which indicates strong density gradient, while the non-thermal X-rays are found toward the less dense inner part of the HI cavity. The most significant non-thermal X-rays are seen toward the southwestern part of the shell where HI gas includes the dense and cold component. We also identified CO clouds which are likely interacting with the SNR shock waves in the same velocity range with HI whereas the CO clouds are distributed only in a limited part of the SNR shell. The most massive cloud is located in the southeastern part of the shell, showing detailed correspondence with the thermal X-rays. These CO clouds show an enhanced CO $J$ = 2-1/1-0 intensity ratio, suggesting heating/compression by the shock front. We interpret the present results that the shock-cloud interaction enhances non-thermal X-rays in the southwest and the thermal X-rays are emitted from the shock-heated gas of density 10-100 cm$^{-3}$. It seems likely that the progenitor of RCW 86 had low-velocity stellar winds with the white dwarf(s), because the thermal X-rays indicate the remaining medium density HI gas which was not fully swept up by the progenitor winds.

[37]  arXiv:1606.07790 [pdf, other]
Title: Small scale problems of the $Λ$CDM model: a short review
Comments: 42pp 19 figs submitted to Galaxies. 2016
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

The $\Lambda$CDM model, or concordance cosmology, as it is often called, is a paradigm at its maturity. It has been checked against a large quantity of observations, and it passed almost all tests.
The paradigm is clearly able to describe the universe at large scale, even if some issues remain open, like the cosmological constant problem, or the unexplained anomalies in the CMB. However, $\Lambda$CDM clearly shows difficulty at small scales, that could be related to our scant understanding, from the nature of dark matter to that of gravity, or to the role of baryon physics, which is not well understood and implemented in simulation codes or in semi-analytic models. At this stage, it is of fundamental importance to understand if the problems encountered by the $\Lambda$DCM model are a sign of its limits or a sign of our failures in getting the finer details right. In the present paper, we will review the small scale problems of the $\Lambda$CDM model, we will discuss the proposed solutions and to what extent they are able to give us a theory accurately describing the phenomena in the complete range of scale of the observed universe.