Publications & Talks

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Submitted and accepted

Title Constraining the CO intensity mapping power spectrum at intermdiate redshifts
Authors Padmanabhan, H.
Publication submitted 2017
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Abstract

We compile available constraints on the carbon monoxide (CO) 1-0 luminosity functions and abundances at redshifts 0-3. This is used to develop a data driven halo model for the evolution of the CO galaxy abundances and clustering across intermediate redshifts. It is found that the recent constraints from the CO Power Spectrum Survey ($z \sim 3$; Keating et al. 2016), when combined with existing observations of local galaxies ($z \sim 0$; Keres et al. 2003), lead to predictions which are consistent with the results of smaller surveys at intermediate redshifts ($z \sim 1-2$). We provide convenient fitting forms for the evolution of the CO luminosity - halo mass relation, and estimates of the mean and uncertainties in the CO power spectrum in the context of future intensity mapping experiments.

Title Oscillations in the 45-5000 MHz Radio Spectrum of the 18 April 2014 Flare
Authors Karlicky, M.; Rybak, J.; Monstein, C.
Publication submitted to Solar Physics 2017
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Abstract

Using a new type of oscillation map, made from the radio spectra by the wavelet technique, we study the 18 April 2014 M7.3 flare (SOL2014-04-18T13:03:00L245C017). We find a quasi-periodic character of this flare with periods in the range 65-115 seconds. At the very beginning of this flare, in connection with the drifting pulsation structure (plasmoid ejection) we find the 65-115 s oscillation phase drifting slowly towards lower frequencies, which indicates an upward propagating wave initiated at the start of the magnetic reconnection. In the drifting pulsation structure many periods (1-200 seconds) are found documenting multi-scale and multi-periodic processes. On this drifting structure fiber bursts with a characteristic period of about one second are superimposed, whose frequency drift is similar to that of the drifting 65-115 s oscillation phase. We also check periods found in this flare by EUV Imaging Spectrometer (EIS)/Hinode and Interface Region Imaging Spectrograph (IRIS) observations. We recognize the type III bursts (electron beams) as proposed, but their time coincidence with the EIS and IRIS peaks is not very good. This is probably due to the radio spectrum beeing a whole-disk record consisting of all bursts from any location while the EIS and IRIS peaks are emitted only from locations of slits in the EIS and IRIS observations.

Title The redshift distribution of cosmological samples: a forward modeling approach
Authors Herbel, J.; Kacprzak, T.; Amara, A.; Refregier, A.; Bruderer, C.; Nicola, A.
Publication submitted to Journal of Cosmology and Astropartice Physics 2017
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Abstract

Determining the redshift distribution $n(z)$ of galaxy samples is essential for several cosmological probes including weak lensing. For imaging surveys, this is usually done using photometric redshifts estimated on an object-by-object basis. We present a new approach for directly measuring the global $n(z)$ of cosmological galaxy samples, including uncertainties, using forward modeling. Our method relies on image simulations produced using UFig (Ultra Fast Image Generator) and on ABC (Approximate Bayesian Computation) within the $MCCL$ (Monte-Carlo Control Loops) framework. The galaxy population is modeled using parametric forms for the luminosity functions, spectral energy distributions, sizes and radial profiles of both blue and red galaxies. We apply exactly the same analysis to the real data and to the simulated images, which also include instrumental and observational effects. By adjusting the parameters of the simulations, we derive a set of acceptable models that are statistically consistent with the data. We then apply the same cuts to the simulations that were used to construct the target galaxy sample in the real data. The redshifts of the galaxies in the resulting simulated samples yield a set of $n(z)$ distributions for the acceptable models. We demonstrate the method by determining $n(z)$ for a cosmic shear like galaxy sample from the 4-band Subaru Suprime-Cam data in the COSMOS field. We also complement this imaging data with a spectroscopic calibration sample from the VVDS survey. We compare our resulting posterior $n(z)$ distributions to the one derived from photometric redshifts estimated using 36 photometric bands in COSMOS and find good agreement. This offers good prospects for applying our approach to current and future large imaging surveys.

Title Search for Neutrinos from Dark Matter Self-Annihilations in the center of the Milky Way with 3 years of IceCube/DeepCore
Authors IceCube Collaboration et al.
Publication submitted 2017
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Abstract

We present a search for a neutrino signal from dark matter self-annihilations in the Milky Way using the IceCube Neutrino Observatory (IceCube). In 1005 days of data we found no significant excess of neutrinos over the background of neutrinos produced in atmospheric air showers from cosmic ray interactions. We derive upper limits on the velocity averaged product of the dark matter self-annihilation cross section and the relative velocity of the dark matter particles $\langle\sigma_{\text{A}}v\rangle$. Upper limits are set for dark matter particle candidate masses ranging from 10 GeV up to 1 TeV while considering annihilation through multiple channels. This work sets the most stringent limit on a neutrino signal from dark matter with mass between 10 GeV and 100 GeV, with a limit of $1.18\cdot10^{-23}\text{cm}^3\text{s}^{-1}$ for 100 GeV dark matter particles self-annihilating via $\tau^+\tau^-$ to neutrinos (assuming the Navarro-Frenk-White dark matter halo profile).

Title Search for astrophysical sources of neutrinos using cascade events in IceCube
Authors IceCube Collaboration et al.
Publication submitted 2017
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Abstract

The IceCube neutrino observatory has established the existence of a flux of high-energy astrophysical neutrinos inconsistent with the expectation from atmospheric backgrounds at a significance greater than $5\sigma$. This flux has been observed in analyses of both track events from muon neutrino interactions and cascade events from interactions of all neutrino flavors. Searches for astrophysical neutrino sources have focused on track events due to the significantly better angular resolution of track reconstructions. To date, no such sources have been confirmed. Here we present the first search for astrophysical neutrino sources using cascades interacting in IceCube with deposited energies as small as 1 TeV. No significant clustering was observed in a selection of 263 cascades collected from May 2010 to May 2012. We show that compared to the classic approach using tracks, this statistically-independent search offers improved sensitivity to sources in the southern sky, especially if the emission is spatially extended or follows a soft energy spectrum. This enhancement is due to the low background from atmospheric neutrinos forming cascade events and the additional veto of atmospheric neutrinos at declinations $\lesssim-30^\circ$.

Title "Non-cold" dark matter at small scales: a general approach
Authors Murgia, R.; Merle, A.; Viel, M.; Totzauer, M.; Schneider, A.
Publication submitted 2017
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Abstract

Structure formation at small cosmological scales provides an important frontier for dark matter (DM) research. Scenarios with small DM particle masses, large momenta or hidden interactions tend to suppress the gravitational clustering at small scales. The details of this suppression depend on the DM particle nature, allowing for a direct link between DM models and astrophysical observations. However, most of the astrophysical constraints obtained so far refer to a very specific shape of the power suppression, corresponding to thermal warm dark matter (WDM), i.e., candidates with a Fermi-Dirac or Bose-Einstein momentum distribution. In this work we introduce a new analytical fitting formula for the power spectrum, which is simple yet flexible enough to reproduce the clustering signal of large classes of non-thermal DM models, which are not at all adequately described by the oversimplified notion of WDM. We show that the formula is able to fully cover the parameter space of sterile neutrinos (whether resonantly produced or from particle decay), mixed cold and warm models, fuzzy dark matter, as well as other models suggested by effective theory of structure formation (ETHOS). Based on this fitting formula, we perform a large suite of N-body simulations and we extract important nonlinear statistics, such as the matter power spectrum and the halo mass function. Finally, we present the first preliminary astrophysical constraints from both the number of Milky Way satellites and the Lyman-{\alpha} forest. This paper is a first step towards a general and comprehensive modeling of small-scale departures from the standard cold DM model.

Title Testing the sterile neutrino dark matter paradigm with astrophysical observations
Authors Schneider A.
Publication submitted to Conference Proceedings NOW 2016 (Conference C16-09-04)
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Abstract

Sterile neutrino dark matter is expected to suppress structure formation at small astrophysical scales. The details of the suppression depend on the sterile neutrino production mechanism in the early universe. In this proceeding, we focus on the most popular cases of resonant production (via the mixing between active and sterile neutrinos) and scalar decay production (via the decay of a hypothetical scalar singlet). We first review current constraints from structure formation before discussing how the sterile neutrino dark matter hypothesis can alleviate the overabundance problem of dwarf galaxies in the local universe.

Title Cosmic Information, the Cosmological Constant and the Amplitude of primordial perturbations
Authors Padmanabhan, T.; Padmanabhan, H.
Publication submitted 2017
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Abstract

A unique feature of gravity is its ability to control the information accessible to any specific observer. We quantify the notion of cosmic information ('CosmIn') for an eternal observer in the universe. Demanding the finiteness of CosmIn requires the universe to have a late-time accelerated expansion. Combining the introduction of CosmIn with generic features of the quantum structure of spacetime (e.g., the holographic principle), we present a holistic model for cosmology. We show that (i) the numerical value of the cosmological constant, as well as (ii) the amplitude of the primordial, scale invariant, perturbation spectrum can be determined in terms of a single free parameter, which specifies the energy scale at which the universe makes a transition from a pre-geometric phase to the classical phase. For a specific value of the parameter, we obtain the correct results for both (i) and (ii). This formalism also shows that the quantum gravitational information content of spacetime can be tested using precision cosmology.

Title Core or cusps: The central dark matter profile of a redshift one strong lensing cluster with a bright central image
Authors Collett, T. E.; Buckley-Greer, E.; Lin, H. et al.
Publication submitted 2017
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Abstract

We report on SPT-CLJ2011-5228, a giant system of arcs created by a cluster at $z=1.06$. The arc system is notable for the presence of a bright central image. The source is a Lyman Break galaxy at $z_s=2.39$ and the mass enclosed within the 14 arc second radius Einstein ring is $10^{14.2}$ solar masses. We perform a full light profile reconstruction of the lensed images to precisely infer the parameters of the mass distribution. The brightness of the central image demands that the central total density profile of the lens be shallow. By fitting the dark matter as a generalized Navarro-Frenk-White profile---with a free parameter for the inner density slope---we find that the break radius is $270^{+48}_{-76}$ kpc, and that the inner density falls with radius to the power $-0.38\pm0.04$ at 68 percent confidence. Such a shallow profile is in strong tension with our understanding of relaxed cold dark matter halos; dark matter only simulations predict the inner density should fall as $r^{-1}$. The tension can be alleviated if this cluster is in fact a merger; a two halo model can also reconstruct the data, with both clumps (density going as $r^{-0.8}$ and $r^{-1.0}$) much more consistent with predictions from dark matter only simulations. At the resolution of our Dark Energy Survey imaging, we are unable to choose between these two models, but we make predictions for forthcoming Hubble Space Telescope imaging that will decisively distinguish between them.

Title Models of the strongly lensed quasar DES J0408-5354
Authors Agnello, A.; Lin, H.; Buckley-Geer, L. et al.
Publication submitted to Monthly Notices of the Royal Astronomical Society 2017
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Abstract

We present gravitational lens models of the multiply imaged quasar DES J0408-5354, recently discovered in the Dark Energy Survey (DES) footprint, with the aim of interpreting its remarkable quad-like configuration. We first model the DES single-epoch $grizY$ images as a superposition of a lens galaxy and four point-like objects, obtaining spectral energy distributions (SEDs) and relative positions for the objects. Three of the point sources (A,B,D) have SEDs compatible with the discovery quasar spectra, while the faintest point-like image (G2/C) shows significant reddening and a `grey' dimming of $\approx0.8$mag. In order to understand the lens configuration, we fit different models to the relative positions of A,B,D. Models with just a single deflector predict a fourth image at the location of G2/C but considerably brighter and bluer. The addition of a small satellite galaxy ($R_{\rm E}\approx0.2$") in the lens plane near the position of G2/C suppresses the flux of the fourth image and can explain both the reddening and grey dimming. All models predict a main deflector with Einstein radius between $1.7"$ and $2.0",$ velocity dispersion $267-280$km/s and enclosed mass $\approx 6\times10^{11}M_{\odot},$ even though higher resolution imaging data are needed to break residual degeneracies in model parameters. The longest time-delay (B-A) is estimated as $\approx 85$ (resp. $\approx125$) days by models with (resp. without) a perturber near G2/C. The configuration and predicted time-delays of J0408-5354 make it an excellent target for follow-up aimed at understanding the source quasar host galaxy and substructure in the lens, and measuring cosmological parameters. We also discuss some lessons learnt from J0408-5354 on lensed quasar finding strategies, due to its chromaticity and morphology.

Title The Einstein-Boltzmann equations revisited
Authors Nadkarni-Ghosh, S.; Refregier, A.
Publication submitted to Monthly Notices of the Royal Astronomical Society 2016
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Abstract

The linear Einstein-Boltzmann equations describe the evolution of perturbations in the universe and its numerical solutions play a central role in cosmology. We revisit this system of differential equations and present a detailed investigation of its mathematical properties. For this purpose, we focus on a simplified set of equations aimed at describing the broad features of the matter power spectrum. We first perform an eigenvalue analysis and study the onset of oscillations in the system signalled by the transition from real to complex eigenvalues. We then provide a stability criterion of different numerical schemes for this linear system and estimate the associated step-size. We show how the stiffness of the system can be characterised in terms of the eigenvalues. While the parameters of the system are time dependent making it non-autonomous, we define an adiabatic regime where the parameters vary slowly enough for the system to be quasi-autonomous. We summarise the different regimes of the system for these different criteria as function of wave number $k$ and scale factor $a$. We also provide a compendium of analytic solutions for all perturbation variables in 6 limits on the $k$-$a$ plane and express them explicitly in terms of initial conditions. These results are aimed to help the further development and testing of numerical cosmological Boltzmann solvers.

Title Integrated Cosmological Probes: Extended Analysis
Authors Nicola, A.; Refregier, A.; Amara, A.
Publication submitted to Physical Review D 2016
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Abstract

Recent progress in cosmology has relied on combining different cosmological probes. In earlier work, we implemented an integrated approach to cosmology where the probes are combined into a common framework at the map level. This has the advantage of taking full account of the correlations between the different probes, to provide a stringent test of systematics and of the validity of the cosmological model. We extend this analysis to include not only CMB temperature, galaxy clustering, weak lensing from SDSS but also CMB lensing, weak lensing from the DES SV survey, Type Ia SNe and $H_{0}$ measurements. This yields 12 auto and cross power spectra as well as background probes. Furthermore, we extend the treatment of systematic uncertainties. For $\Lambda$CDM, we find results that are consistent with our earlier work. Given our enlarged data set and systematics treatment, this confirms the robustness of our analysis and results. Furthermore, we find that our best-fit cosmological model gives a good fit to the data we consider with no signs of tensions within our analysis. We also find our constraints to be consistent with those found by WMAP9, SPT and ACT and the KiDS weak lensing survey. Comparing with the Planck Collaboration results, we see a broad agreement, but there are indications of a tension from the marginalized constraints in most pairs of cosmological parameters. Since our analysis includes CMB temperature Planck data at $10 < \ell < 610$, the tension appears to arise between the Planck high$-\ell$ and the other measurements. Furthermore, we find the constraints on the probe calibration parameters to be in agreement with expectations, showing that the data sets are mutually consistent. In particular, this yields a confirmation of the amplitude calibration of the weak lensing measurements from SDSS, DES SV and Planck CMB lensing from our integrated analysis.

Title A halo model for cosmological neutral hydrogen: abundances and clustering
Authors Padmanabhan, H.; Refregier, A.; Amara, A.
Publication submitted 2016
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Abstract

We extend the results of previous analyses towards constraining the abundance and clustering of post-reionization ($z \sim 0-5$) neutral hydrogen (HI) systems using a halo model framework. We work with a comprehensive HI dataset including the small-scale clustering, column density and mass function of HI galaxies at low redshifts, intensity mapping measurements at intermediate redshifts and the UV/optical observations of Damped Lyman Alpha (DLA) systems at higher redshifts. We use a Markov Chain Monte Carlo (MCMC) approach to constrain the parameters of the best-fitting models, both for the HI-halo mass relation and the HI radial density profile. We find that a radial exponential profile results in a good fit to the low-redshift HI observations, including the clustering and the column density distribution. The form of the profile is also found to match the high-redshift DLA observations, when used in combination with a three-parameter HI-halo mass relation and a redshift evolution in the HI concentration. The halo model predictions are in good agreement with the observed HI surface density profiles of low-redshift galaxies, and the general trends in the the impact parameter and covering fraction observations of high-redshift DLAs. We provide convenient tables summarizing the best-fit halo model predictions.

Title Hints against the cold and collisionless nature of dark matter from the galaxy velocity function
Authors Schneider, A.; Trujillo-Gomez, S. et al.
Publication submitted 2016
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Abstract

The observed number of dwarf galaxies as a function of rotation velocity is significantly smaller than predicted by the $\Lambda$CDM model. This discrepancy cannot be simply solved by assuming strong baryonic processes, since they would violate the observed relation between maximum circular velocity ($v_{\rm max}$) and baryon mass of galaxies. A speculative but tantalising possibility is that the mismatch between observation and theory points towards the existence of non-cold or non-collisionless dark matter (DM). In this paper, we investigate the effects of warm, mixed (i.e warm plus cold), and self-interacting DM scenarios on the abundance of dwarf galaxies and the relation between observed HI line-width and maximum circular velocity. Both effects have the potential to alleviate the apparent mismatch between the observed and theoretical abundance of galaxies as a function of $v_{\rm max}$. For the case of warm and mixed DM, we show that the discrepancy disappears, even for luke-warm models that evade stringent bounds from the Lyman-$\alpha$ forest. Self-interacting DM scenarios can also provide a solution as long as they lead to extended ($\gtrsim 1.5$ kpc) dark matter cores in the density profiles of dwarf galaxies. Only models with velocity-dependent cross sections can yield such cores without violating other observational constraints at larger scales.

 

Title The DESI Experiment Part I: Science, Targeting, and Survey Design
Authors DESI Collaboration, Aghamousa, A.; Aguilar, J.; Ahlen, S. et al.
Publication submitted 2016
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Abstract

DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. To trace the underlying dark matter distribution, spectroscopic targets will be selected in four classes from imaging data. We will measure luminous red galaxies up to $z=1.0$. To probe the Universe out to even higher redshift, DESI will target bright [O II] emission line galaxies up to $z=1.7$. Quasars will be targeted both as direct tracers of the underlying dark matter distribution and, at higher redshifts ($ 2.1 < z < 3.5$), for the Ly-$\alpha$ forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen. When moonlight prevents efficient observations of the faint targets of the baseline survey, DESI will conduct a magnitude-limited Bright Galaxy Survey comprising approximately 10 million galaxies with a median $z\approx 0.2$. In total, more than 30 million galaxy and quasar redshifts will be obtained to measure the BAO feature and determine the matter power spectrum, including redshift space distortions.

Title The DESI Experiment Part II: Instrument Design
Authors DESI Collaboration, Aghamousa, A.; Aguilar, J.; Ahlen, S. et al.
Publication submitted 2016
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Abstract

DESI (Dark Energy Spectropic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. The DESI instrument is a robotically-actuated, fiber-fed spectrograph capable of taking up to 5,000 simultaneous spectra over a wavelength range from 360 nm to 980 nm. The fibers feed ten three-arm spectrographs with resolution $R= \lambda/\Delta\lambda$ between 2000 and 5500, depending on wavelength. The DESI instrument will be used to conduct a five-year survey designed to cover 14,000 deg$^2$. This powerful instrument will be installed at prime focus on the 4-m Mayall telescope in Kitt Peak, Arizona, along with a new optical corrector, which will provide a three-degree diameter field of view. The DESI collaboration will also deliver a spectroscopic pipeline and data management system to reduce and archive all data for eventual public use.

Title Weak-lensing mass calibration of redMaPPer galaxy clusters in Dark Energy Survey Science Verification Data
Authors Melchior, P.; Gruen, D.; McClintok, T.; Varga, T.N.; Sheldon, E., Rozo, E.; Amara, A. et al.
Publication submitted to Monthly Notices of the Royal Astronomical Society 2016
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Abstract

We use weak-lensing shear measurements to determine the mean mass of optically selected galaxy clusters in Dark Energy Survey Science Verification data. In a blinded analysis, we split the sample of more than 8,000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter $5 \leq \lambda \leq 180$ and redshift $0.2 \leq z \leq 0.8$, and fit the averaged mass density contrast profiles with a model that accounts for seven distinct sources of systematic uncertainty: shear measurement and photometric redshift errors; cluster-member contamination; miscentering; deviations from the NFW halo profile; halo triaxiality; and line-of-sight projections. We combine the inferred cluster masses to estimate the joint scaling relation between mass, richness and redshift, $\mathcal{M}(\lambda,z) \varpropto M_0 \lambda^{F} (1+z)^{G}$. We find $M_0 \equiv \langle M_{200\mathrm{m}}\,|\,\lambda=30,z=0.5\rangle=\left[ 2.35 \pm 0.22\ \rm{(stat)} \pm 0.12\ \rm{(sys)} \right] \cdot 10^{14}\ M_\odot$, with $F = 1.12\,\pm\,0.20\ \rm{(stat)}\, \pm\, 0.06\ \rm{(sys)}$ and $G = 0.18\,\pm\, 0.75\ \rm{(stat)}\, \pm\, 0.24\ \rm{(sys)}$. The amplitude of the mass-richness relation is in excellent agreement with the weak-lensing calibration of redMaPPer clusters in SDSS by Simet et al. (2016) and with the Saro et al. (2015) calibration based on abundance matching of SPT-detected clusters. Our results extend the redshift range over which the mass-richness relation of redMaPPer clusters has been calibrated with weak lensing from $z\leq 0.3$ to $z\leq0.8$. Calibration uncertainties of shear measurements and photometric redshift estimates dominate our systematic error budget and require substantial improvements for forthcoming studies.

Title Update on BINGO 21cm intensity mapping experiment
Authors Battye, R.; Browne, I.; Chen, T.; Dickinson, C., Harper, S. et al.
Publication submitted to Proceedings of Recontres de Moriond, La Thuille, 22-29 March 2014
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Abstract

21cm intensity mapping is a novel approach aimed at measuring the power spectrum of density fluctuations and deducing cosmological information, notably from the Baryonic Acoustic Oscillations (BAO). We give an update on the progress of BAO from Integrated Neutral Gas Observations (BINGO) which is a single dish intensity mapping project. First we explain the basic ideas behind intensity mapping concept before updating the instrument design for BINGO. We also outline the survey we plan to make and its projected science output including estimates of cosmological parameters.

Title Quantitative Evaluation of Gender Bias in Astronomical Publications from Citation Counts
Authors Caplar, N.; Tachella, S.; Birrer, S.
Publication submitted to Nature Astronomy 2016
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Abstract

We analyze the role of first (leading) author gender on the number of citations that a paper receives, on the publishing frequency and on the self-citing tendency. We consider a complete sample of over 200,000 publications from 1950 to 2015 from five major astronomy journals. We determine the gender of the first author for over 70% of all publications. The fraction of papers which have a female first author has increased from less than 5% in the 1960s to about 25% today. We find that the increase of the fraction of papers authored by females is slowest in the most prestigious journals such as Science and Nature. Furthermore, female authors write 19$\pm$7% fewer papers in seven years following their first paper than their male colleagues. At all times papers with male first authors receive more citations than papers with female first authors. This difference has been decreasing with time and amounts to $\sim$6% measured over the last 30 years. To account for the fact that the properties of female and male first author papers differ intrinsically, we use a random forest algorithm to control for the non-gender specific properties of these papers which include seniority of the first author, number of references, total number of authors, year of publication, publication journal, field of study and region of the first author's institution. We show that papers authored by females receive 10.4$\pm$0.9% fewer citations than what would be expected if the papers with the same non-gender specific properties were written by the male authors. Finally, we also find that female authors in our sample tend to self-cite more, but that this effect disappears when controlled for non-gender specific variables.

Title Another baryon miracle? Testing solutions to the "missing dwarfs" problem
Authors Trujillo-Gomez, S.; Schneider, A. et al.
Publication submitted 2016
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Abstract

No explanation exists so far for the observed dearth of dwarf galaxies in the local universe compared to the large number of dark matter halos predicted by $\Lambda$CDM. Although attempts have been made to attribute the discrepancy to observational systematics, this would require an extreme modification of the density profiles of haloes through baryonic processes. In this paper we perform a systematic evaluation of the uncertainties affecting the measurement of DM halo abundance using galaxy kinematics. Including observational systematics and modelling uncertainties, we derive the abundance of galaxies as a function of maximum circular velocity --a direct probe of mass-- from the observed line-of-sight velocity function in the Local Volume. This provides a direct means of comparing the predictions of theoretical models and simulations (including nonstandard cosmologies and novel galaxy formation physics) to the observational constraints. The new "galactic $V_{max}$" function is steeper than the line-of-sight velocity function but still shallower than the theoretical CDM VF, showing that some unaccounted physical process is necessary to reduce the abundance of galaxies and/or drastically modify their density profiles compared to CDM haloes. Using this new galactic $V_{max}$ function, we investigate the viability of baryonic solutions such as photoevaporation of gas from an ionising background as well as stellar feedback. However, we find that the observed relation between baryonic mass and $V_{max}$ places tight constraints on the maximum suppression from reionisation. Neither energetic feedback nor photoevaporation are effective enough to reconcile the disagreement. This might point to the need to modify cosmological predictions at small scales.

Title Galaxy bias from galaxy-galaxy lensing in DES Science Verification Data
Authors Prat, J.; Sanchez, C.; Miguel, R.; Kwan, J.; Blazek, J., Bonnett, C.; Amara, A.
Publication submitted to Monthly Notices of the Royal Astronomical Society 2016
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Abstract

We present a measurement of galaxy-galaxy lensing around a magnitude-limited (iAB<22.5) sample of galaxies selected from the Dark Energy Survey Science Verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias b and cross-correlation coefficient between the galaxy and dark matter overdensity fields r in each bin, using scales above 4 Mpc/h comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy-galaxy lensing with those obtained from galaxy clustering (Crocce et al. 2016) and CMB lensing (Giannantonio et al. 2016) for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al. (2016), while, in the lowest redshift bin (z0.3), they show some tension with the findings in Giannantonio et al. (2016). Our results are found to be rather insensitive to a large range of systematic effects. We measure br to be 0.87±0.11, 1.12±0.16 and 1.24±0.23, respectively for the three redshift bins of width Δz=0.2 in the range 0.2<z<0.8, defined with the photometric-redshift algorithm BPZ. Using a different code to split the lens sample, TPZ, leads to changes in the measured biases at the 10-20% level, but it does not alter the main conclusion of this work: when comparing with Crocce et al. (2016) we do not find strong evidence for a cross-correlation parameter significantly below one in this galaxy sample, except possibly at the lowest redshift bin (z0.3), where we find r=0.71±0.11 when using TPZ, and 0.83±0.12 with BPZ, assuming the difference between the results from the two probes can be solely attributed to the cross-correlation parameter.

Title Constraints on the evolution of the relationship between HI mass and halo mass in the last 12 Gyr
Authors Padmanabhan, H.; Kulkarni, G.
Publication submitted to Monthly Notices of the Royal Astronomical Society 2016
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Abstract

The neutral hydrogen (HI) content of dark matter haloes forms an intermediate state in the baryon cycle that connects the hot shock-heated gas and cold star-forming gas in haloes. Measurement of the relationship between HI mass and halo mass therefore puts important constraints on galaxy formation models. We combine radio observations of HI in emission at low redshift ($z\sim 0$) with optical/UV observations of HI in absorption at high redshift ($1<z<4$) to derive constraints on the evolution of the HI-mass halo-mass (HIHM) relation from redshift $z=4$ to $z=0$. We model the evolution of the HIHM relation in a manner similar to that of the stellar-halo mass (SHM) relation. Combining this parameterisation with a redshift- and mass-dependent modified Navarro-Frenk-White (NFW) profile for the HI density within a halo, we draw constraints on the evolution of the HIHM relation from the observed HI column density, incidence rate, and clustering bias at high redshift. We find that the peak HI mass fraction moderately increases from 1% at $z=0$ to about 3.1% at $z=4$. The corresponding halo mass increases from $10^{11.7}$ M$_\odot$ to $10^{12.4}$ M$_\odot$. The data do not suggest a strong evolution in the HI density profile. Predictions of this model are in excellent agreement with the observed column density distribution and incidence rate of high-column-density HI absorption-line systems at high redshift, although the agreement is poor with the column density distribution at $z=0$. The increase in the halo mass with maximum HI mass fraction also enables the model predictions to successfully match the measured clustering bias of high column density HI systems at $z=2.3$. We discuss the resultant evolution of the HIHM relation and its consequences for HI and galaxy evolution.

Title Baryonic effects on weak-lensing two-point statistics and its cosmological implications
Authors Mohammed, I.; Martizzi, D.; Teyssier, R.; Amara, A.
Publication submitted to Monthly Notices of the Royal Astronomical Society 2014
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Abstract

We develop an extension of \textit{the Halo Model} that describes analytically the corrections to the matter power spectrum due to the physics of baryons. We extend these corrections to the weak-lensing shear angular power spectrum. Within each halo, our baryonic model accounts for: 1) a central galaxy, the major stellar component whose properties are derived from abundance matching techniques; 2) a hot plasma in hydrostatic equilibrium and 3) an adiabatically-contracted dark matter component. This analytic approach allows us to compare our model to the dark-matter-only case. Our basic assumptions are tested against the hydrodynamical simulations of Martizzi et. al. (2014), with which a remarkable agreement is found. Our baryonic model has only one free parameter, $M_{\rm crit}$, the critical halo mass that marks the transition between feedback-dominated halos, mostly devoid of gas, and gas rich halos, in which AGN feedback effects become weaker. We explore the entire cosmological parameter space, using the angular power spectrum in three redshift bins as the observable, assuming a Euclid-like survey. We derive the corresponding constraints on the cosmological parameters, as well as the possible bias introduced by neglecting the effects of baryonic physics. We find that, up to $\ell_{max}$=4000, baryonic physics plays very little role in the cosmological parameters estimation. However, if one goes up to $\ell_{max}$=8000, the marginalized errors on the cosmological parameters can be significantly reduced, but neglecting baryonic physics can lead to bias in the recovered cosmological parameters up to 10$\sigma$. These biases are removed if one takes into account the main baryonic parameter, $M_{\rm crit}$, which can also be determined up to 1-2\%, along with the other cosmological parameters.

Published

Searching for cosmic strings in CMB anisotropy maps using wavelets and curvelets
Lukas Hergt, Adam Amara, Robert Brandenberger, Tomasz Kacprzak and Alexandre Réfrégier
Journal of Cosmology and Astroparticle Physics (JCAP), 2017 (6): 004, Bristol: Institute of Physics, 2017.
Lensing substructure quantification in RXJ1131-1231: a 2 keV lower bound on dark matter thermal relic mass
Simon Birrer, Adam Amara and Alexandre Refregier
Journal of Cosmology and Astroparticle Physics, 2017 (05): 037, Bristol: Institute of Physics, 2017.
Line-of-sight effects in strong lensing: putting theory into practice
Simon Birrer, Welschen Cyril, Adam Amara and Alexandre Refregier
Journal of Cosmology and Astroparticle Physics (JCAP), 4: 49, Bristol: Institute of Physics, 2017.
Testing the lognormality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps
L. Clerkin, D. Kirk, M. Manera, O. Lahav, F. Abdalla, Adam Amara, D. Bacon, C. Chang, E. Gaztañaga, A. Hawken, B. Jain, B. Joachimi, V. Vikram, T. Abbott, S. Allam, R. Armstrong, A. Benoit-Lévy, G.M. Bernstein, R.A. Bernstein, E. Bertin, D. Brooks, D.L. Burke, A. Carnero Rosell, M. Carrasco Kind, M. Crocce, C.E. Cunha, C.B. D'Andrea, L.N. da Costa, S. Desai, H.T. Diehl, J.P. Dietrich, T.F. Eifler, A.E. Evrar, B. Flaugher, P. Fosalba, J. Frieman, D.W. Gerdes, D. Gruen, R.A. Gruendl, G. Gutierrez, K. Honscheid, D.J. James, S. Kent, K. Kuehn, N. Kuropatkin, M. Lima, P. Melchior, R. Miquel, B. Nord, A.A. Plazas, A.K. Romer, A. Roodman, E. Sanchez, M. Schubnell, I. Sevilla-Noarbe, R.C. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, M.E.C. Swanson, G. Tarle and A.R. Walker
Monthly Notices of the Royal Astronomical Society, 466 (2): 1444-1461, Oxford: Oxford University Press, 2017.
Discovery of the Lensed Quasar System DES J0408-5354
DES Collaboration, H. Lin, Adam Amara and et al.
The Astrophysical Journal Letters, 838 (2): L15, Bristol: Institute of Physics, 2017.
Updated core libraries of the ALPS project
Alexander Gaenko, Andrey E. Antipov, G. Carcassi, T. Chen, X. Chen, Qiaoyuan Dong, Lukas Gamper, Jan Gukelberger, Ryo Igarashi, Sergei N. Iskakov, Markus Könz, James P.F. LeBlanc, R. Levy, Pingnang Ma, J.E. Paki, Hiroshi Shinaoka, Synge Todo, Matthias Troyer and Emanuel Gull
Computer Physics Communications, 213: 235-251, Amsterdam: Elsevier, 2017.
Inference from the small scales of cosmic shear with current and future Dark Energy Survey data
Niall MacCrann, Jelena Aleksić, Adam Amara, Sarah L. Bridle, Claudio Bruderer, Chihway Chang, Scott Dodelson, Tim F. Eifler, Eric M. Huff, Dragan Huterer, Tomasz Kacprzak, Alexandre Réfrégier, Eric Suchyta, Risa H. Wechsler, Joe Zuntz, Timothy M.C. Abbott, Sahar Allam, James Annis, Ryan Armstrong, Aurélien Benoit-Lévy, David Brooks, David L. Burke, Aurelio Carnero Rosell, M. Carrasco Kind, Jorge Carretero, Francisco J. Castander, Martín Crocce, Carlos E. Cunha, Luis N. da Costa, Shantanu Desai, H. Thomas Diehl, Jörg P. Dietrich, Peter Doel, August E. Evrard, Brenna Flaugher, Pablo Fosalba, David W. Gerdes, Daniel A. Goldstein, Daniel Gruen, Robert A. Gruendl, Gaston Gutierrez, Klaus Honscheid, David J. James, Mike Jarvis, Elisabeth Krause, Kyler Kuehn, Nikolay Kuropatkin, Marcos Lima, Jonathon L. Marshall, Peter Melchior, F. Menanteau, Ramon Miquel, Andrés A. Plazas, A. Kathy Römer, Eli S. Rykoff, Enmanuel Sánchez, Victor Scarpine, Ignacio Sevilla-Noarbe, Erin Sheldon, Marcelle Soares-Santos, Molly E.C. Swanson, Gregory Tarlé, Daniel Thomas and Vinu Vikram
Monthly Notices of the Royal Astronomical Society, 465 (3): 2567-2583, Oxford: Oxford University Press, 2017.
Strain-Engineered Oxygen Vacancies in CaMnO3 Thin Films
Ravini U. Chandrasena, Weibing Yang, Qingyu Lei, Mario U. Delgado-Jaime, Kanishka D. Wijesekara, Maryam Golalikhani, Bruce A. Davidson, Elke Arenholz, Keisuke Kobayashi, Masaaki Kobata, Frank M.F. de Groot, Ulrich Aschauer, Nicola A. Spaldin, Xiaoxing Xi and Alexander X. Gray
Nano Letters, 17 (2): 794-799, Washington, DC: American Chemical Society, 2017.
Activation of mitochondrial protein phosphatase SLP2 by MIA40 regulates seed germination
R. Glen Uhrig, Anne-Marie Labandera, Lay-Yin Tang, Nicolas A. Sieben, Marilyn Goudreault, Edward Yeung, Anne-Claude Gingras, Marcus A. Samuel and Greg B.G. Moorhead
Plant Physiology, 173 (2): 956-969, Rockville, MD: American Society of Plant Physiologists, 2017.
Defect Chemistry as a Crystal Structure Design Parameter: Intrinsic Point Defects and Ga Substitution in InMnO3
Sinéad M. Griffin, Mari Reidulff, Sverre M. Selbach and Nicola A. Spaldin
Chemistry of Materials, 29 (6): 2425-2434, Washington, DC: American Chemical Society, 2017.
 
 
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22.07.2017
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