Distinguishing between optical coherent states with imperfect detection

Several proposed techniques for distinguishing between optical coherent states are analyzed under a physically realistic model of photodetection. Quantum error probabilities are derived for the Kennedy receiver, the Dolinar receiver and the unitary rotation scheme proposed by Sasaki and Hirota for sub-unity detector efficiency. Monte carlo simulations are performed to assess the effects of detector dark counts, dead time, signal processing bandwidth and phase noise in the communication channel. The feedback strategy employed by the Dolinar receiver is found to achieve the Helstrom bound for sub-unity detection efficiency and to provide robustness to these other detector imperfections making it more attractive for laboratory implementation than previously believed

High-Resolution Infrared Imaging of Herschel 36 SE: A Showcase for the Influence of Massive Stars in Cluster Environments

We present high-resolution infrared imaging of the massive star-forming region around the O-star Herschel 36. Special emphasis is given to a compact infrared source at 0".25 southeast of the star. The infrared source, hereafter Her 36 SE, is extended in the broad-band images, but features spatially unresolved Br gamma line emission. The line-emission source coincides in position with the previous HST detections in H alpha and the 2 cm radio continuum emission detected by VLA interferometry. We propose that the infrared source Her 36 SE harbors an early B-type star, deeply embedded in a dusty cloud. The fan shape of the cloud with Herschel 36 at its apex, though, manifests direct and ongoing destructive influence of the O7V star on Her 36 SE

Constraints on core-collapse supernova progenitors from explosion site integral field spectroscopy

Observationally, supernovae (SNe) are divided into subclasses pertaining to their distinct characteristics. This diversity reflects the diversity in the progenitor stars. It is not entirely clear how different evolutionary paths leading massive stars to become a SN are governed by fundamental parameters such as progenitor initial mass and metallicity. This paper places constraints on progenitor initial mass and metallicity in distinct core-collapse SN subclasses, through a study of the parent stellar populations at the explosion sites. Integral field spectroscopy (IFS) of 83 nearby SN explosion sites with a median distance of 18 Mpc has been collected and analysed, enabling detection and spectral extraction of the parent stellar population of SN progenitors. From the parent stellar population spectrum, the initial mass and metallicity of the coeval progenitor are derived by means of comparison to simple stellar population models and strong-line methods. Additionally, near-infrared IFS was employed to characterise the star formation history at the explosion sites. No significant metallicity differences are observed among distinct SN types. The typical progenitor mass is found to be highest for SN Ic, followed by type Ib, then types IIb and II. SN IIn is the least associated with young stellar populations and thus massive progenitors. However, statistically significant differences in progenitor initial mass are observed only when comparing SNe IIn with other subclasses. Stripped-envelope SN progenitors with initial mass estimate lower than 25~$M_\odot$ are found; these are thought to be the result of binary progenitors. Confirming previous studies, these results support the notion that core-collapse SN progenitors cannot arise from single-star channel only, and both single and binary channels are at play in the production of core-collapse SNe. [ABRIDGED]Comment: 18 pages, 10 figures, accepted to A&

Sumo Puff: Tidal Debris or Disturbed Ultra-Diffuse Galaxy?

We report the discovery of a diffuse stellar cloud with an angular extent $\gtrsim30^{\prime\prime}$, which we term "Sumo Puff", in data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). While we do not have a redshift for this object, it is in close angular proximity to a post-merger galaxy at redshift $z=0.0431$ and is projected within a few virial radii (assuming similar redshifts) of two other ${\sim}L_\star$ galaxies, which we use to bracket a potential redshift range of $0.0055 < z < 0.0431$. The object's light distribution is flat, as characterized by a low Sersic index ($n\sim0.3$). It has a low central $g$-band surface brightness of ${\sim}26.4$ mag arcsec$^{-2}$, large effective radius of ${\sim}13^{\prime\prime}$ (${\sim}11$ kpc at $z=0.0431$ and ${\sim}1.5$ kpc at $z=0.0055$), and an elongated morphology ($b/a\sim0.4$). Its red color ($g-i\sim1$) is consistent with a passively evolving stellar population and similar to the nearby post-merger galaxy, and we may see tidal material connecting Sumo Puff with this galaxy. We offer two possible interpretations for the nature of this object: (1) it is an extreme, galaxy-size tidal feature associated with a recent merger event, or (2) it is a foreground dwarf galaxy with properties consistent with a quenched, disturbed ultra-diffuse galaxy. We present a qualitative comparison with simulations that demonstrates the feasibility of forming a structure similar to this object in a merger event. Follow-up spectroscopy and/or deeper imaging to confirm the presence of the bridge of tidal material will be necessary to reveal the true nature of this object.Comment: 10 pages, 5 figures, submitted to PASJ for the HSC-SSP special issu

The LAOG-Planet Imaging Surveys

With the development of high contrast imaging techniques and infrared detectors, vast efforts have been devoted during the past decade to detect and characterize lighter, cooler and closer companions to nearby stars, and ultimately image new planetary systems. Complementary to other observing techniques (radial velocity, transit, micro-lensing, pulsar-timing), this approach has opened a new astrophysical window to study the physical properties and the formation mechanisms of brown dwarfs and planets. I here will briefly present the observing challenge, the different observing techniques, strategies and samples of current exoplanet imaging searches that have been selected in the context of the LAOG-Planet Imaging Surveys. I will finally describe the most recent results that led to the discovery of giant planets probably formed like the ones of our solar system, offering exciting and attractive perspectives for the future generation of deep imaging instruments.Comment: 6 pages, 5 figures, Invited talk of "Exoplanets and disks: their formation and diversity" conference, 9-12 March 200

A new quadruple gravitational lens from the Hyper Suprime-Cam Survey: the puzzle of HSC~J115252+004733

We report the serendipitous discovery of a quadruply lensed source at $z_{\rm s}=3.76$, HSC~J115252+004733, from the Hyper Suprime-Cam (HSC) Survey. The source is lensed by an early-type galaxy at $z_{\rm l}=0.466$ and a satellite galaxy. Here, we investigate the properties of the source by studying its size and luminosity from the imaging and the luminosity and velocity width of the Ly-$\alpha$ line from the spectrum. Our analyses suggest that the source is most probably a low-luminosity active galactic nucleus (LLAGN) but the possibility of it being a compact bright galaxy (e.g., a Lyman-$\alpha$ emitter or Lyman Break Galaxy) cannot be excluded. The brighter pair of lensed images appears point-like except in the HSC $i$-band (with a seeing $\sim0.5"$). The extended emission in the $i$-band image could be due to the host galaxy underneath the AGN, or alternatively, due to a highly compact lensed galaxy (without AGN) which appears point-like in all bands except in $i$-band. We also find that the flux ratio of the brighter pair of images is different in the Ks-band compared to optical wavelengths. Phenomena such as differential extinction and intrinsic variability cannot explain this chromatic variation. While microlensing from stars in the foreground galaxy is less likely to be the cause, it cannot be ruled out completely. If the galaxy hosts an AGN, then this represents the highest redshift quadruply imaged AGN known to date, enabling study of a distant LLAGN. Discovery of this unusually compact and faint source demonstrates the potential of the HSC survey.Comment: 9 pages, 7 figures, 3 Tables, MNRAS accepted, text reduce

Hot and Diffuse Clouds near the Galactic Center Probed by Metastable H3+

Using an absorption line from the metastable (J, K) = (3, 3) level of H3+ together with other lines of H3+ and CO observed along several sightlines, we have discovered a vast amount of high temperature (T ~ 250 K) and low density (n ~ 100 cm-3) gas with a large velocity dispersion in the Central Molecular Zone (CMZ) of the Galaxy, i.e., within 200 pc of the center. Approximately three fourths of the H3+ along the line of sight to the brightest source we observed, the Quintuplet object GCS 3-2, is inferred to be in the CMZ, with the remaining H3+ located in intervening spiral arms. About half of H3+ in the CMZ has velocities near ~ - 100 km s-1 indicating that it is associated with the 180 pc radius Expanding Molecular Ring which approximately forms outer boundary of the CMZ. The other half, with velocities of ~ - 50 km s-1 and ~ 0 km s-1, is probably closer to the center. CO is not very abundant in those clouds. Hot and diffuse gas in which the (3, 3) level is populated was not detected toward several dense clouds and diffuse clouds in the Galactic disk where large column densities of colder H3+ have been reported previously. Thus the newly discovered environment appears to be unique to the CMZ. The large observed H3+ column densities in the CMZ suggests an ionization rate much higher than in the diffuse interstellar medium in the Galactic disk. Our finding that the H3+ in the CMZ is almost entirely in diffuse clouds indicates that the reported volume filling factor (f &#8805; 0.1) for n &#8805; 104 cm-3 clouds in the CMZ is an overestimate by at least an order of magnitude.Comment: 33 pages, 5 figures, 3 table

X-Ray Magnetic Circular Dichroism at the K edge of Mn3GaC

We theoretically investigate the origin of the x-ray magnetic circular dichroism (XMCD) spectra at the K edges of Mn and Ga in the ferromagnetic phase of Mn3GaC on the basis of an ab initio calculation. Taking account of the spin-orbit interaction in the LDA scheme, we obtain the XMCD spectra in excellent agreement with the recent experiment. We have analyzed the origin of each structure, and thus elucidated the mechanism of inducing the orbital polarization in the p symmetric states. We also discuss a simple sum rule connecting the XMCD spectra with the orbital moment in the p symmetric states.Comment: 5 pages, 5 figures, accepted for publication in Physical Review

Direct Imaging of a Cold Jovian Exoplanet in Orbit around the Sun-like Star GJ 504

Several exoplanets have recently been imaged at wide separations of >10 AU from their parent stars. These span a limited range of ages (<50 Myr) and atmospheric properties, with temperatures of 800--1800 K and very red colors (J - H > 0.5 mag), implying thick cloud covers. Furthermore, substantial model uncertainties exist at these young ages due to the unknown initial conditions at formation, which can lead to an order of magnitude of uncertainty in the modeled planet mass. Here, we report the direct imaging discovery of a Jovian exoplanet around the Sun-like star GJ 504, detected as part of the SEEDS survey. The system is older than all other known directly-imaged planets; as a result, its estimated mass remains in the planetary regime independent of uncertainties related to choices of initial conditions in the exoplanet modeling. Using the most common exoplanet cooling model, and given the system age of 160 [+350, -60] Myr, GJ 504 b has an estimated mass of 4 [+4.5, -1.0] Jupiter masses, among the lowest of directly imaged planets. Its projected separation of 43.5 AU exceeds the typical outer boundary of ~30 AU predicted for the core accretion mechanism. GJ 504 b is also significantly cooler (510 [+30, -20] K) and has a bluer color (J-H = -0.23 mag) than previously imaged exoplanets, suggesting a largely cloud-free atmosphere accessible to spectroscopic characterization. Thus, it has the potential of providing novel insights into the origins of giant planets, as well as their atmospheric properties.Comment: 20 pages, 12 figures, Accepted for publication in ApJ. Minor updates from the version