Abstracts of Interest
Selected by:
Kirsty Feijen
Abstract: 1809.08020
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Deep XMM-Newton observations of the northern disc of M31. I. Source catalogue
(Submitted on 21 Sep 2018)
Abstract: We carried out new observations of two fields in the northern ring of M31 with XMM-Newton with two exposures of 100 ks each and obtained a complete list of X-ray sources down to a sensitivity limit of ~7 x 10^34 erg s^-1 (0.5 - 2.0 keV). The major objective of the observing programme was the study of the hot phase of the ISM in M31. The analysis of the diffuse emission and the study of the ISM is presented in a separate paper. We analysed the spectral properties of all detected sources using hardness ratios and spectra if the statistics were high enough. We also checked for variability. We cross-correlated the source list with the source catalogue of a new survey of the northern disc of M31 carried out with Chandra and Hubble (Panchromatic Hubble Andromeda Treasury, PHAT) as well as with other existing catalogues. We detected a total of 389 sources, including 43 foreground stars and candidates and 50 background sources. Based on the comparison to the Chandra/PHAT survey, we classify 24 hard X-ray sources as new candidates for X-ray binaries (XRBs). In total, we identified 34 XRBs and candidates and 18 supernova remnants (SNRs) and candidates. Three of the four brightest SNRs show emission mainly below 2 keV, consistent with shocked ISM. The spectra of two of them also require an additional component with a higher temperature. The SNR [SPH11] 1535 has a harder spectrum and might suggest that there is a pulsar-wind nebula inside the SNR. We find five new sources showing clear time variability. We also studied the spectral properties of the transient source SWIFT J004420.1+413702, which shows significant variation in flux over a period of seven months (June 2015 to January 2016) and associated change in absorption. Based on the likely optical counterpart detected in the Chandra/PHAT survey, the source is classified as a low-mass X-ray binary.
Abstract: 1809.05777
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Search for high-energy neutrino emission from Mrk 421 and Mrk 501 with the ANTARES neutrino telescope
(Submitted on 15 Sep 2018)
Abstract: ANTARES is the largest high-energy neutrino telescope in the Northern Hemisphere. This contribution presents the results of a search, based on the ANTARES data collected over 17 months between November 2014 and April 2016, for high energy neutrino emission in coincidence with TeV $\gamma$-ray flares from Markarian 421 and Markarian 501, two bright BL Lac extragalactic sources highly variable in flux, detected by the HAWC observatory. The analysis is based on an unbinned likelihood-ratio maximization method. The $\gamma$-ray lightcurves (LC) for each source were used to search for temporally correlated neutrinos, that would be produced in pp or p-$\gamma$ interactions. The impact of different flare selection criteria on the discovery neutrino flux is discussed. Plausible neutrino spectra derived from the observed $\gamma$-ray spectra in addition to generic spectra $E^{-2}$ and $E^{-2.5}$ are tested.
Abstract: 1809.06642
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: FOREST Unbiased Galactic Plane Imaging Survey with the Nobeyama 45-m Telescope (FUGIN) V: Dense gas mass fraction of molecular gas in the Galactic plane
(Submitted on 18 Sep 2018)
Abstract: Recent observations of the nearby Galactic molecular clouds indicate that the dense gas in molecular clouds have quasi-universal properties on star formation, and observational studies of extra galaxies have shown a galactic-scale correlation between the star formation rate (SFR) and surface density of molecular gas. To reach a comprehensive understanding of both properties, it is important to quantify the fractional mass of the dense gas in molecular clouds f_DG. In particular, for the Milky Way (MW), there are no previous studies resolving the f_DG disk over a scale of several kpc. In this study, the f_DG was measured over 5kpc in the first quadrant of the MW, based on the CO J=1-0 data in l=10-50 deg obtained as part of the FOREST Unbiased Galactic Plane Imaging Survey with the Nobeyama 45-m Telescope (FUGIN) project. The total molecular mass was measured using 12CO, and the dense gas mass was estimated using C18O. The fractional masses including f_DG in the region within ~30% of the distances to the tangential points of the Galactic rotation (e.g., the Galactic Bar, Far-3kpc Arm, Norma Arm, Scutum Arm, Sagittarius Arm, and inter-arm regions) were measured. As a result, an averaged f_DG of 2.9^{+2.1}_{-0.8} % was obtained for the entirety of the target region. This low value suggests that dense gas formation is the primary factor of inefficient star formation in galaxies. It was also found that the f_DG shows large variations depending on the structures in the MW disk. The f_DG in the Galactic arms were estimated to be ~4-5%, while those in the bar and inter-arm regions were as small as ~0.1-0.4%. These results indicate that the formation/destruction processes of the dense gas and their timescales are different for different regions in the MW, leading to the differences in SFRs.
Abstract: 1809.06782
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: TeV-PeV neutrino-nucleon cross section measurement with 5 years of IceCube data
(Submitted on 18 Sep 2018)
Abstract: We present a novel analysis method for the determination of the neutrino-nucleon Deep Inelastic Scattering (DIS) cross section in the TeV - PeV energy range utilizing neutrino absorption by the Earth. We analyze five years of data collected with the complete IceCube detector from May 2011 to May 2016. This analysis focuses on electromagnetic and hadronic showers (cascades) mainly induced by electron and tau neutrinos. The applied event selection features high background rejection (< 10% background contamination below 60 TeV, background free above 60 TeV) of atmospheric muons and high signal efficiency (~ 80%). The final neutrino sample consists of 4808 events, with 402 events above 10 TeV reconstructed energy. An unfolding method was applied to enable the mapping from reconstructed cascade parameters such as energy and zenith to true neutrino variables. The analysis was performed assuming isotropic astrophysical neutrino flux, in seven energy bins, and in two zenith bins ("down-going" from the south-hemisphere and "up-going" from the north-hemisphere). The ratio of down-going to up-going events (which are absorbed by the Earth at high energies) is sensitive to the neutrino-nucleon cross section but insensitive to the astrophysical neutrino flux uncertainties.
Abstract: 1809.07227
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: A Template-based $γ$-ray Reconstruction Method for Air Shower Arrays
(Submitted on 19 Sep 2018)
Abstract: We introduce a new Monte Carlo template-based reconstruction method for air shower arrays, with a focus on shower core and energy reconstruction of $\gamma$-ray induced air showers. The algorithm fits an observed lateral amplitude distribution of an extensive air shower against an expected probability distribution using a likelihood approach. A full Monte Carlo air shower simulation in combination with the detector simulation is used to generate the expected probability distributions. The goodness of fit can be used to discriminate between $\gamma$-ray and hadron induced air showers. As an example, we apply this method to the High Altitude Water Cherenkov $\gamma$-ray Observatory and its recently installed high-energy upgrade. The performance of this method and the applicability to air shower arrays with mixed detector types makes it a promising reconstruction approach for current and future instruments.
Abstract: 1809.07194
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Fickian and non-Fickian diffusion of cosmic rays
(Submitted on 19 Sep 2018)
Abstract: Fluid approximations to cosmic ray (CR) transport are often preferred to kinetic descriptions in studies of the dynamics of the interstellar medium (ISM) of galaxies, because they allow simpler analytical and numerical treatments. Magnetohydrodynamic (MHD) simulations of the ISM usually incorporate CR dynamics as an advection-diffusion equation for CR energy density, with anisotropic, magnetic field-aligned diffusion with the diffusive flux assumed to obey Fick's law. We compare test-particle and fluid simulations of CRs in a random magnetic field. We demonstrate that a non-Fickian prescription of CR diffusion, which corresponds to the telegraph equation for the CR energy density, can be easily calibrated to match the test particle simulations with great accuracy. In particular, we consider a random magnetic field in the fluid simulation that has a lower spatial resolution than that used in the particle simulation to demonstrate that an appropriate choice of the diffusion tensor can account effectively for the unresolved (subgrid) scales of the magnetic field. We show that the characteristic time which appears in the telegraph equation can be physically interpreted as the time required for the particles to reach a diffusive regime and we stress that the Fickian description of the CR fluid is unable to describe complex boundary or initial conditions for the CR energy flux.
Abstract: 1809.07351
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: The Origins Space Telescope
(Submitted on 19 Sep 2018)
Abstract: The Origins Space Telescope, one of four large Mission Concept studies sponsored by NASA for review in the 2020 US Astrophysics Decadal Survey, will open unprecedented discovery space in the infrared, unveiling our cosmic origins. We briefly describe in this article the key science themes and architecture for OST. With a sensitivity gain of up to a factor of 1,000 over any previous or planned mission, OST will open unprecedented discovery space, allow us to peer through an infrared window teeming with possibility. OST will fundamentally change our understanding of our cosmic origins - from the growth of galaxies and black holes, to uncovering the trail of water, to life signs in nearby Earth-size planets, and discoveries never imagined. Built to be highly adaptable, while addressing key science across many areas of astrophysics, OST will usher in a new era of infrared astronomy.
Abstract: 1809.07336
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: JINGLE, a JCMT legacy survey of dust and gas for galaxy evolution studies: I. Survey overview and first results
(Submitted on 19 Sep 2018)
Abstract: JINGLE is a new JCMT legacy survey designed to systematically study the cold interstellar medium of galaxies in the local Universe. As part of the survey we perform 850um continuum measurements with SCUBA-2 for a representative sample of 193 Herschel-selected galaxies with M*>10^9Msun, as well as integrated CO(2-1) line fluxes with RxA3m for a subset of 90 of these galaxies. The sample is selected from fields covered by the Herschel-ATLAS survey that are also targeted by the MaNGA optical integral-field spectroscopic survey. The new JCMT observations combined with the multi-wavelength ancillary data will allow for the robust characterization of the properties of dust in the nearby Universe, and the benchmarking of scaling relations between dust, gas, and global galaxy properties. In this paper we give an overview of the survey objectives and details about the sample selection and JCMT observations, present a consistent 30 band UV-to-FIR photometric catalog with derived properties, and introduce the JINGLE Main Data Release (MDR). Science highlights include the non-linearity of the relation between 850um luminosity and CO line luminosity, and the serendipitous discovery of candidate z>6 galaxies.
Abstract: 1809.07164
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Resolving the X-ray obscuration in a low flux observation of the quasar PDS 456
(Submitted on 19 Sep 2018)
Abstract: Simultaneous XMM-Newton, NuSTAR and HST observations, performed in March 2017, of the nearby ($z=0.184$) luminous quasar PDS 456 are presented. PDS 456 had a low X-ray flux compared to past observations, where the first of the two new XMM-Newton observations occurred during a pronounced dip in the X-ray lightcurve. The broad-band X-ray spectrum is highly absorbed, attenuated by a soft X-ray absorber of column density $N_{\rm H}=6\times10^{22}$ cm$^{-2}$. An increase in obscuration occurs during the dip, which may be due to an X-ray eclipse. In addition, the persistent, fast Fe K outflow is present, with velocity components of $-0.25c$ and $-0.4c$. The soft absorber is less ionized ($\log\xi=3$) compared to the iron K outflow ($\log\xi=5$) and is outflowing with a velocity of approximately $-0.2c$. A soft X-ray excess is present below 1 keV against the highly absorbed continuum and can be attributed to the re-emission from a wide angle wind. The complex X-ray absorption present in PDS 456 suggests that the wind is inhomogeneous, whereby the soft X-ray absorber originates from denser clumps or filaments which may form further out along the outflow. In contrast to the X-ray observations, the simultaneous UV spectrum of PDS 456 is largely unabsorbed, where only a very weak broad absorption trough is present bluewards of Ly$\alpha$, compared to a past observation in 2000 when the trough was significantly stronger. The relative weakness of the UV absorption may be due to the soft X-ray absorber being too highly ionized and almost transparent in the UV band.
Abstract: 1809.07323
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Blazar jets as the most efficient persistent engines
(Submitted on 19 Sep 2018)
Abstract: We have not identified for sure what is the mechanism launching, accelerating and collimating relativistic jets. The two most likely possibilities are the gravitational energy of the accreting matter or the rotational energy of a spinning black hole. Even the evaluation of the jet power is not trivial, since the radiation from the jet is enhanced by relativistic beaming, and there are fundamental uncertainties concerning the matter content of the jet (electron--proton or electron--positron plasma). However, in recent years, there have been crucial advances mainly driven by the richness of data in the $\gamma$-ray band. This is the band where blazars emit most of their electromagnetic power. Furthermore, there are now large sample of $\gamma$-ray loud blazars covered by optical spectroscopy. For the blazar sub-class of flat spectrum radio quasars (FSRQ) these data provide measurements of the main emission lines and of the underlying continuum. From these data, it is relatively easy to infer the bolometric luminosity of the accretion disk. The relativistic jet emission on one hand, and the disk luminosity on the other hand, allows us to compare the jet power and the accretion luminosity. Although the inferred jet power is subject to a few assumptions and is somewhat model--dependent, it is possible to derive a lower limit to the jet power that is assumption-free and model-independent. Since this lower limit is of the order of the accretion luminosity, we infer that the true jet power is larger.
Abstract: 1809.07528
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Solenoidal improvements for the JF12 Galactic magnetic field model
(Submitted on 20 Sep 2018)
Abstract: The popular JF12 analytic model by Jansson & Farrar (2012) provides a quantitative description of the Galaxy's large-scale magnetic field that is widely used in various astrophysical applications. However, both the poloidal X-type component and the spiral disk component of JF12 exhibit regions in which the magnetic divergence constraint is severely violated. We first propose a cure for this problem, resulting in a truly solenoidal large-scale field. Second, the otherwise straight field lines of the X-type component exhibit kinks in the Galactic plane that, in addition to implying the presence of a singular current sheet, may pose difficulties for, e.g., numerical tracing of cosmic-ray particles. We propose and discuss two possible strategies to mitigate this problem. All corrections are kept as minimal as possible in order not to destroy the agreement to observational data that the unmodified JF12 field is based on. Furthermore, the performance of our improved version of the field model is quantitatively assessed by test simulations using the CRPropa Galactic cosmic-ray propagation code.
Abstract: 1809.07261
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: Search for High-Mass Protostellar Objects in Cold IRAS Sources
(Submitted on 19 Sep 2018)
Abstract: We present the results of CS J=2-1 mapping observations towards 39 massive star-forming regions selected from the previous CO line survey of cold IRAS sources with high-velocity CO flows along the Galactic plane (Yang et al. 2002). All sources are detected in CS J=2-1 showing the existence of CS clumps around the IRAS sources. However, one-third of the sources are not deeply embedded in the dense clumps by comparison of the central powering IRAS sources and the morphologies of CS clumps. Physical parameters of the dense molecular clumps are presented. We have identified 12 high-mass protostellar object (HMPO) candidates by checking the association between the dense cores and the IRAS sources, the detection of water maser, and the radio properties towards the IRAS sources. We find that the HMPO sources are characterized by low FIR luminosity to virial mass ratios since they are in very early evolutionary stages when the massive protostars have not reached their full luminosities, which are typical for zero-age main sequence stars. Large turbulent motion in the HMPO sources may be largely due to the large kinetic energy ejected by the central protostars formed in the dense clumps. However, alternative means or undetected outflows may also be responsible for the turbulence in the clumps.
Abstract: 1809.05967
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: TESS Discovery of a Transiting Super-Earth in the $Π$ Mensae System
(Submitted on 16 Sep 2018)
Abstract: We report the detection of a transiting planet around $\pi$ Mensae (HD\,39091), using data from the Transiting Exoplanet Survey Satellite (TESS). The solar-type host star is unusually bright (V=5.7) and was already known to host a Jovian planet on a highly eccentric, 5.7-year orbit. The newly discovered planet has a size of 2.14$\pm$ 0.04~$R_\oplus$ and an orbital period of 6.27 days. Radial-velocity data from the HARPS and AAT/UCLES archives also displays a 6.27-day periodicity, confirming the existence of the planet and leading to a mass determination of 4.82$\pm$ 0.85~$M_\oplus$. The star's proximity and brightness will facilitate further investigations, such as atmospheric spectroscopy, asteroseismology, the Rossiter-McLaughlin effect, astrometry, and direct imaging.
Abstract: 1809.06385
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title: How high is the neutrino floor?
(Submitted on 17 Sep 2018)
Abstract: In this paper, we compute the contribution to the coherent elastic neutrino-nucleus scattering cross section from new physics models in the neutrino sector. We use this information to calculate the maximum value of the so-called neutrino floor for direct dark matter detection experiments, which determines when these detectors are sensitive to the neutrino background. After including all relevant experimental constraints in different simplified neutrino models, we have found that the neutrino floor can increase by various orders of magnitude in the region of dark matter masses below 10 GeV in the case of scalar mediators, whereas the increase is approximately a factor of two for vector mediators. In the light of these results, future claims by direct detection experiments exploring the low-mass window must be carefully examined if a signal is found well above the expected Standard Model neutrino floor.
This page created: Tue Sep 25 10:08:11 ACST 2018 by kfeijen
For a printable title listing click here
For details on generating this page see the instructions. If there are problems with this page (and I expect there will be from time to time) contact Jose.
For previous lists of abstracts of interest click Previous abstracts of interest