A novel 3D technique to study the kinematics of lensed galaxies

We present a 3D Bayesian method to model the kinematics of strongly lensed galaxies from spatially-resolved emission-line observations. This technique enables us to simultaneously recover the lens-mass distribution and the source kinematics directly from the 3D data cube. We have tested this new method with simulated OSIRIS observations for nine star-forming lensed galaxies with different kinematic properties. The simulated rotation curves span a range of shapes which are prototypes of different morphological galaxy types, from dwarf to massive spiral galaxies. We have found that the median relative accuracy on the inferred lens and kinematic parameters are at the level of 1 and 2 per cent, respectively. We have also tested the robustness of the technique against different inclination angles, signal-to-noise ratios, the presence of warps or non-circular motions and we have found that the accuracy stays within a few per cent in most cases. This technique represents a significant step forward with respect to the methods used until now, as the lens parameters and the kinematics of the source are derived from the same 3D data. This enables us to study the possible degeneracies between the two and estimate the uncertainties on all model parameters consistently.Comment: Accepted for publication in MNRA

The angular momentum-mass relation: a fundamental law from dwarf irregulars to massive spirals

In a $\Lambda$CDM Universe, the specific stellar angular momentum ($j_\ast$) and stellar mass ($M_\ast$) of a galaxy are correlated as a consequence of the scaling existing for dark matter haloes ($j_{\rm h}\propto M_{\rm h}^{2/3}$). The shape of this law is crucial to test galaxy formation models, which are currently discrepant especially at the lowest masses, allowing to constrain fundamental parameters, e.g. the retained fraction of angular momentum. In this study, we accurately determine the empirical $j_\ast-M_\ast$ relation (Fall relation) for 92 nearby spiral galaxies (from S0 to Irr) selected from the Spitzer Photometry and Accurate Rotation Curves (SPARC) sample in the unprecedented mass range $7 \lesssim \log M_\ast/M_\odot \lesssim 11.5$. We significantly improve all previous estimates of the Fall relation by determining $j_\ast$ profiles homogeneously for all galaxies, using extended HI rotation curves, and selecting only galaxies for which a robust $j_\ast$ could be measured (converged $j_\ast(<R)$ radial profile). We find the relation to be well described by a single, unbroken power-law $j_\ast\propto M_\ast^\alpha$ over the entire mass range, with $\alpha=0.55\pm 0.02$ and orthogonal intrinsic scatter of $0.17\pm 0.01$ dex. We finally discuss some implications for galaxy formation models of this fundamental scaling law and, in particular, the fact that it excludes models in which discs of all masses retain the same fraction of the halo angular momentum.Comment: A&A Letters, accepte

Laser induced modulation of the Landau level structure in single-layer graphene

We present perturbative analytical results of the Landau level quasienergy spectrum, autocorrelation function and out of plane pseudospin polarization for a single graphene sheet subject to intense circularly polarized terahertz radiation. For the quasienergy spectrum, we find a striking non trivial level-dependent dynamically induced gap structure. This photoinduced modulation of the energy band structure gives rise to shifts of the revival times in the autocorrelation function and it also leads to modulation of the oscillations in the dynamical evolution of the out of plane pseudospin polarization, which measures the angular momentum transfer between light and graphene electrons. For a coherent state, chosen as an initial pseudospin configuration, the dynamics induces additional quantum revivals of the wave function that manifest as shifts of the maxima and minima of the autocorrelation function, with additional partial revivals and beating patterns. These additional maxima and beating patterns stem from the effective dynamical coupling of the static eigenstates. We discuss the possible experimental detection schemes of our theoretical results and their relevance in new practical implementation of radiation fields in graphene physics.Comment: 12 pages, 5 figures. Accepted version for publication in Physical Review

(3D) BAROLO: a new 3D algorithm to derive rotation curves of galaxies

We present 3D3DBAROLO,† a new code that derives rotation curves of galaxies from emission-line observations. This software fits 3D tilted-ring models to spectroscopic data cubes and can be used with a variety of observations: from H I and molecular lines to optical/IR recombination lines. We describe the structure of the main algorithm and show that it performs much better than the standard 2D approach on velocity fields. A number of successful applications, from high to very low spatial resolution data are presented and discussed. 3D3DBAROLO can recover the true rotation curve and estimate the intrinsic velocity dispersion even in barely resolved galaxies (∼2 resolution elements) provided that the signal to noise of the data is larger than 2–3. It can also be run automatically thanks to its source-detection and first-estimate modules, which make it suitable for the analysis of large 3D data sets. These features make 3D3DBAROLO a uniquely useful tool to derive reliable kinematics for both local and high-redshift galaxies from a variety of different instruments including the new generation Integral Field Units, ALMA and the SKA pathfinders

The Effect of Laser Bandwidth on the Signal Detected in Two-Color, Resonant Four-Wave Mixing Spectroscopy

The effect of laser line shape and bandwidth on the signal detected in two-color, resonant four-wave mixing (TC-RFWM) spectroscopy is determined by means of an ab initio calculation of the third-order polarization based on diagrammatic perturbation theory. Modifications to the approach previously used for the case of delta-function laser line shapes are made by introducing a different treatment of the rotating wave approximation and phase-matching conditions. A three-level excitation scheme for double-resonance spectroscopy of bound and quasibound states is analyzed. In the case of Lorentzian laser line shapes, analytic expressions for the signal line profile are obtained for each excitation scheme. Analytic approximations of the signal line profile are also obtained in the case of Gaussian laser line shapes. (C) 1999 American Institute of Physics. [S0021-9606(99)01917-0]

Theoretical Treatment of Quasibound Resonances in Two-Color Resonant Four-Wave Mixing Spectroscopy

A treatment of continuum states in the application of diagrammatic perturbation theory to calculate the signal produced in two-color resonant four-wave mixing (TC-RFWM) spectroscopy is developed. The third-order susceptibility is significantly modified from that obtained when considering only discrete states. To illustrate the contribution of continuum states, the line profile of a quasibound resonance arising from the configuration interaction of bound and continuum states is derived. Analytic expressions for line profiles are presented for two specific experimental implementations of TC-RFWM used in gas-phase spectroscopic studies. While the TC-RFWM line profiles are found to be very distinct from the line profiles measured in linear spectroscopic techniques, the results demonstrate the important capability to characterize the TC-RFWM line profiles in terms of the same fundamental and physically significant parameters

The Effect of Laser Bandwidth on the Signal Detected in Two-Color, Resonant Four-Wave Mixing Spectroscopy

The effect of laser line shape and bandwidth on the signal detected in two-color, resonant four-wave mixing (TC-RFWM) spectroscopy is determined by means of an ab initio calculation of the third-order polarization based on diagrammatic perturbation theory. Modifications to the approach previously used for the case of delta-function laser line shapes are made by introducing a different treatment of the rotating wave approximation and phase-matching conditions. A three-level excitation scheme for double-resonance spectroscopy of bound and quasibound states is analyzed. In the case of Lorentzian laser line shapes, analytic expressions for the signal line profile are obtained for each excitation scheme. Analytic approximations of the signal line profile are also obtained in the case of Gaussian laser line shapes. (C) 1999 American Institute of Physics. [S0021-9606(99)01917-0]

Gas accretion from minor mergers in local spiral galaxies

We quantify the gas accretion rate from minor mergers onto star-forming galaxies in the local Universe using Hi observations of 148 nearby spiral galaxies (WHISP sample). We developed a dedicated code that iteratively analyses Hi data-cubes, finds dwarf gas-rich satellites around larger galaxies, and estimates an upper limit to the gas accretion rate. We found that 22% of the galaxies have at least one detected dwarf companion. We made the very stringent assumption that all satellites are going to merge in the shortest possible time, transferring all their gas to the main galaxies. This leads to an estimate of the maximum gas accretion rate of 0.28 M⊙ yr-1, about five times lower than the average star formation rate of the sample. Given the assumptions, our accretion rate is clearly an overestimate. Our result strongly suggests that minor mergers do not play a significant role in the total gas accretion budget in local galaxies

Theoretical Treatment of Quasibound Resonances in Two-Color Resonant Four-Wave Mixing Spectroscopy

A treatment of continuum states in the application of diagrammatic perturbation theory to calculate the signal produced in two-color resonant four-wave mixing (TC-RFWM) spectroscopy is developed. The third-order susceptibility is significantly modified from that obtained when considering only discrete states. To illustrate the contribution of continuum states, the line profile of a quasibound resonance arising from the configuration interaction of bound and continuum states is derived. Analytic expressions for line profiles are presented for two specific experimental implementations of TC-RFWM used in gas-phase spectroscopic studies. While the TC-RFWM line profiles are found to be very distinct from the line profiles measured in linear spectroscopic techniques, the results demonstrate the important capability to characterize the TC-RFWM line profiles in terms of the same fundamental and physically significant parameters