A highly-ionized region surrounding SN Refsdal revealed by MUSE

Supernova (SN) Refsdal is the first multiply-imaged, highly-magnified, and spatially-resolved SN ever observed. The SN exploded in a highly-magnified spiral galaxy at z=1.49 behind the Frontier Fields Cluster MACS1149, and provides a unique opportunity to study the environment of SNe at high z. We exploit the time delay between multiple images to determine the properties of the SN and its environment, before, during, and after the SN exploded. We use the integral-field spectrograph MUSE on the VLT to simultaneously target all observed and model-predicted positions of SN Refsdal. We find MgII emission at all positions of SN Refsdal, accompanied by weak FeII* emission at two positions. The measured ratios of [OII] to MgII emission of 10-20 indicate a high degree of ionization with low metallicity. Because the same high degree of ionization is found in all images, and our spatial resolution is too coarse to resolve the region of influence of SN Refsdal, we conclude that this high degree of ionization has been produced by previous SNe or a young and hot stellar population. We find no variability of the [OII] line over a period of 57 days. This suggests that there is no variation in the [OII] luminosity of the SN over this period, or that the SN has a small contribution to the integrated [OII] emission over the scale resolved by our observations.Comment: 5 pages, 4 figures, accepted for publication in A&

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]

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

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

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

Ricordo di Carlo Pedretti ideatore e direttore di «Achademia Leonardi Vinci» / To Carlo Pedretti creator and director of «Achademia Leonardi Vinci»

Ricordo di Carlo Pedretti, ideatore e direttore di «Achademia Leonardi Vinci. An International Journal of Leonardo Studies», in apertura della nuova serie della rivista

Flat rotation curves and low velocity dispersions in KMOS star-forming galaxies at z ~ 1

The study of the evolution of star-forming galaxies requires the determination of accurate kinematics and scaling relations out to high redshift. In this paper we select a sample of 18 galaxies at z~1, observed in the H-alpha emission-line with KMOS, to derive accurate kinematics using a novel 3D analysis technique. We use the new code 3D-Barolo, that models the galaxy emission directly in the 3D observational space, without the need to extract kinematic maps. This technique's major advantage is that it is not affected by beam smearing and thus it enables the determination of rotation velocity and intrinsic velocity dispersion, even at low spatial resolution. We find that: 1) the rotation curves of these z~1 galaxies rise very steeply within few kiloparsecs and remain flat out to the outermost radius and 2) the H-alpha velocity dispersions are low, ranging from 15 to 40 km/s, which leads to V/sigma = 3-10. These characteristics are similar to those of disc galaxies in the local Universe. Finally, we also report no significant evolution of the stellar-mass Tully-Fisher relation. Our results show that disc galaxies are kinematically mature and rotation-dominated already at z~1.Comment: Accepted for publication in A&A, 11 pages, 6 figures, 1 tabl

Dynamics of Rydberg States of Nitric Oxide Probed By Two-Color Resonant Four-Wave Mixing Spectroscopy

Two-color resonant four-wave mixing (TC-RFWM) spectroscopy has been used to probe highly excited v = 0 and v = 1 Rydberg states of nitric oxide. Transitions to n = 16-30, v = 0, Rydberg states, and the 8p, 9p, 7f, 8f, 8s, and 9s, v = 1 Rydberg states from the A (2)Sigma(+), v\u27 = 0 and 1 states have been recorded. The decay rate of the 8p and 9p, v = 1 states has been extracted from the observed line profiles by using a recently developed model for the excitation of quasibound resonances in TC-RFWM spectroscopy. Transitions from the A (2)Sigma(+), v\u27 = 1 state to the X (2)Pi(3/2), v = 10 state have also been observed, allowing an absolute calibration of the TC-RFWM signal intensity. This calibration is used to determine an excited-state absorption cross section for the 9p, v = 1 Rydberg state. (C) 1998 American Institute of Physics. [S0021-9606(98)01625-0]