1,755 research outputs found

    IN-SYNC. VIII. Primordial Disk Frequencies in NGC 1333, IC 348, and the Orion A Molecular Cloud

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    In this paper, we address two issues related to primordial disk evolution in three clusters (NGC 1333, IC 348, and Orion A) observed by the INfrared Spectra of Young Nebulous Clusters (IN-SYNC) project. First, in each cluster, averaged over the spread of age, we investigate how disk lifetime is dependent on stellar mass. The general relation in IC 348 and Orion A is that primordial disks around intermediate mass stars (2--5MM_{\odot}) evolve faster than those around loss mass stars (0.1--1MM_{\odot}), which is consistent with previous results. However, considering only low mass stars, we do not find a significant dependence of disk frequency on stellar mass. These results can help to better constrain theories on gas giant planet formation timescales. Secondly, in the Orion A molecular cloud, in the mass range of 0.35--0.7MM_{\odot}, we provide the most robust evidence to date for disk evolution within a single cluster exhibiting modest age spread. By using surface gravity as an age indicator and employing 4.5 μm\mu m excess as a primordial disk diagnostic, we observe a trend of decreasing disk frequency for older stars. The detection of intra-cluster disk evolution in NGC 1333 and IC 348 is tentative, since the slight decrease of disk frequency for older stars is a less than 1-σ\sigma effect.Comment: 25 pages, 26 figures; submitted for publication (ApJ

    High signal-to-noise spectral characterization of the planetary-mass object HD 106906 b

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    We spectroscopically characterize the atmosphere of HD 106906b, a young low-mass companion near the deuterium burning limit. The wide separation from its host star of 7.1" makes it an ideal candidate for high S/N and high-resolution spectroscopy. We aim to derive new constraints on the spectral type, effective temperature, and luminosity of HD106906b and also to provide a high S/N template spectrum for future characterization of extrasolar planets. We obtained 1.1-2.5 μ\mum integral field spectroscopy with the VLT/SINFONI instrument with a spectral resolution of R~2000-4000. New estimates of the parameters of HD 106906b are derived by analyzing spectral features, comparing the extracted spectra to spectral catalogs of other low-mass objects, and fitting with theoretical isochrones. We identify several spectral absorption lines that are consistent with a low mass for HD 106906b. We derive a new spectral type of L1.5±\pm1.0, one subclass earlier than previous estimates. Through comparison with other young low-mass objects, this translates to a luminosity of log(L/LL/L_\odot)=3.65±0.08-3.65\pm0.08 and an effective temperature of Teff=1820±2401820\pm240 K. Our new mass estimates range between M=11.90.8+1.7MJupM=11.9^{+1.7}_{-0.8} M_{\rm Jup} (hot start) and M=14.00.5+0.2MJupM=14.0^{+0.2}_{-0.5} M_{\rm Jup} (cold start). These limits take into account a possibly finite formation time, i.e., HD 106906b is allowed to be 0--3 Myr younger than its host star. We exclude accretion onto HD 106906b at rates M˙>4.8×1010MJup\dot{M}>4.8\times10^{-10} M_{\rm Jup}yr1^{-1} based on the fact that we observe no hydrogen (Paschen-β\beta, Brackett-γ\gamma) emission. This is indicative of little or no circumplanetary gas. With our new observations, HD 106906b is the planetary-mass object with one of the highest S/N spectra yet. We make the spectrum available for future comparison with data from existing and next-generation (e.g., ELT and JWST) spectrographs.Comment: 11 pages, 5 figures. Accepted for publication in Astronomy & Astrophysics. Fully reduced spectra will be made available for download on CD

    Protoplanetary Disk Masses in the Young NGC 2024 Cluster

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    We present the results from a Submillimeter Array survey of the 887 micron continuum emission from the protoplanetary disks around 95 young stars in the young cluster NGC 2024. Emission was detected from 22 infrared sources, with flux densities from ~5 to 330 mJy; upper limits (at 3sigma) for the other 73 sources range from 3 to 24 mJy. For standard assumptions, the corresponding disk masses range from ~0.003 to 0.2Msolar, with upper limits at 0.002--0.01Msolar. The NGC 2024 sample has a slightly more populated tail at the high end of its disk mass distribution compared to other clusters, but without more information on the nature of the sample hosts it remains unclear if this difference is statistically significant or a superficial selection effect. Unlike in the Orion Trapezium, there is no evidence for a disk mass dependence on the (projected) separation from the massive star IRS2b in the NGC 2024 cluster. We suggest that this is due to either the cluster youth or a comparatively weaker photoionizing radiation field.Comment: ApJ, in pres

    Manipulation of the spontaneous emission dynamics of quantum dots in two-dimensional photonic crystals

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    We demonstrate the ability to control the spontaneous emission dynamics of self-assembled quantum dots via the local density of optical modes in 2D-photonic crystals. We show that an incomplete 2D photonic bandgap is sufficient to significantly lengthen the spontaneous emission lifetime (>2×>2\times) over a wide bandwidth (Δλ40\Delta\lambda\geq40 nm). For dots that are both \textit{spectrally} and \textit{spatially} coupled to strongly localized (Vmode1.5(λ/n)3V_{mode}\sim1.5(\lambda/n)^{3}), high Q2700Q\sim2700 optical modes, we have directly measured a strong Purcell enhanced shortening of the emission lifetime 5.6×\geq5.6\times, limited only by our temporal resolution. Analysis of the spectral dependence of the recombination dynamics shows a maximum lifetime shortening of 19±419\pm4. From the directly measured enhancement and suppression we show that the single mode coupling efficiency for quantum dots in such structures is at least β=92\beta=92% and is estimated to be as large as 97\sim97%.Comment: 11 pages, 3 figure

    The Demographics and Atmospheres of Giant Planets with the ELTs

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    Gas giants are the most readily detectable exoplanets but fundamental questions about their system architectures, formation, migration, and atmospheres have been unanswerable with the current generation of ground- and space-based facilities. The dominant techniques to detect and characterize giant planets - radial velocities, transits, direct imaging, microlensing, and astrometry - are each isolated to a limited range of planet masses, separations, ages, and temperatures. These windows into the arrangement and physical properties of giant planets have spawned new questions about the timescale and location of their assembly; the distributions of planet mass and orbital separation at young and old ages; the composition and structure of their atmospheres; and their orbital and rotational angular momentum architectures. The ELTs will address these questions by building bridges between these islands of mass, orbital distance, and age. The angular resolution, collecting area, all-sky coverage, and novel instrumentation suite of these facilities are needed to provide a complete map of the orbits and atmospheric evolution of gas giant planets (0.3-10 MJupM_\mathrm{Jup}) across space (0.1-100 AU) and time (1 Myr to 10 Gyr). This white paper highlights the scientific potential of the GMT and TMT to address these outstanding questions, with a particular focus on the role of direct imaging and spectroscopy of large samples of giant planets that will soon be made available with GaiaGaia.Comment: White paper for the Astro2020 decadal surve