scholarly journals Time variability in the bipolar scattered light nebula of L1527 IRS: a possible warped inner disk

2019 ◽  
Vol 626 ◽  
pp. A51
Author(s):  
Brian T. Cook ◽  
John J. Tobin ◽  
Michael F. Skrutskie ◽  
Matthew J. Nelson
Keyword(s):  
Surface Brightness ◽  
Near Infrared ◽  
Scattered Light ◽  
Time Variability ◽  
Time Varying ◽  
Spatially Resolved ◽  
Near Ir ◽  
Low Mass ◽  
Infrared Wavelengths ◽  
Brightness Variability

Context. The bipolar outflows associated with low-mass protostars create cavities in the infalling envelope. These cavities are illuminated by the central protostar and inner disk, creating a bipolar scattered light nebula at near-infrared and mid-infrared wavelengths. The variability of the scattered light nebula in both total intensity and intensity as a function of position in the scattered light nebula can provide important insights into the structure of the inner disk that cannot be spatially resolved. Aims. We aim to determine the likelihood that a warped inner disk is the origin of the surface brightness variability in the bipolar scattered light nebula associated with L1527 IRS. Methods. We present results from near-IR imaging conducted over the course of seven years, with periods of monthly cadence monitoring. We used Monte Carlo radiative transfer models to interpret the observations. Results. We find a time varying, asymmetrical brightness in the scattered light nebulae within the outflow cavities of the protostar. Starting in 2007, the surface brightnesses of the eastern and western outflow cavities were roughly symmetric. Then, in 2009, the surface brightnesses of the cavities were found to be asymmetric, with a substantial increase in surface brightness and a larger increase in the eastern outflow cavity. More regular monitoring was conducted from 2011 to 2014, revealing a rotating pattern of surface brightness variability in addition to a slow change of the eastern and western outflow cavities toward symmetry, but still not as symmetric as observed in 2007. We find that an inner disk warp is a feasible mechanism to produce the rotating pattern of surface brightness variability.

scholarly journals Spatial segregation of dust grains in transition disks

2019 ◽  
Vol 624 ◽  
pp. A7 ◽  
Author(s):  
M. Villenave ◽  
M. Benisty ◽  
W. R. F. Dent ◽  
F. Ménard ◽  
A. Garufi ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Near Infrared ◽  
Scattered Light ◽  
Radiative Transfer Model ◽  
Occurrence Rate ◽  
Transfer Model ◽  
Star Forming ◽  
Spatially Resolved ◽  
Wide Range ◽  
Transition Disks

Context. The mechanisms governing the opening of cavities in transition disks are not fully understood. Several processes have been proposed, but their occurrence rate is still unknown. Aims. We present spatially resolved observations of two transition disks, and aim at constraining their vertical and radial structure using multiwavelength observations that probe different regions of the disks and can help understanding the origin of the cavities. Methods. We have obtained near-infrared scattered light observations with VLT/SPHERE of the transition disks 2MASS J16083070-3828268 (J1608) and RXJ1852.3-3700 (J1852), located in the Lupus and Corona Australis star-forming regions respectively. We complement our datasets with archival ALMA observations, and with unresolved photometric observations covering a wide range of wavelengths. We performed radiative transfer modeling to analyze the morphology of the disks, and then compare the results with a sample of 20 other transition disks observed with both SPHERE and ALMA. Results. We detect scattered light in J1608 and J1852 up to a radius of 0.54′′ and 0.4′′ respectively. The image of J1608 reveals a very inclined disk (i ~ 74°), with two bright lobes and a large cavity. We also marginally detect the scattering surface from the rear-facing side of the disk. J1852 shows an inner ring extending beyond the coronagraphic radius up to 15 au, a gap and a second ring at 42 au. Our radiative transfer model of J1608 indicates that the millimeter-sized grains are less extended vertically and radially than the micron-sized grains, indicating advanced settling and radial drift. We find good agreement with the observations of J1852 with a similar model, but due to the low inclination of the system, the model remains partly degenerate. The analysis of 22 transition disks shows that, in general, the cavities observed in scattered light are smaller than the ones detected at millimeter wavelengths. Conclusions. The analysis of a sample of transition disks indicates that the small grains, well coupled to the gas, can flow inward of the region where millimeter grains are trapped. While 15 out of the 22 cavities in our sample could be explained by a planet of less than 13 Jupiter masses, the others either require the presence of a more massive companion or of several low-mass planets.

scholarly journals Optical and UV surface brightness of translucent dark nebulae

2018 ◽  
Vol 617 ◽  
pp. A42 ◽  
Author(s):  
K. Mattila ◽  
M. Haas ◽  
L. K. Haikala ◽  
Y-S. Jo ◽  
K. Lehtinen ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Near Infrared ◽  
Scattered Light ◽  
Spectral Energy Distribution ◽  
Fluorescence Emission ◽  
Infrared Emission ◽  
Line Of Sight ◽  
Spectral Energy ◽  
Optical Extinction ◽  
Fluorescent Emission

Context. Dark nebulae display a surface brightness because dust grains scatter light of the general interstellar radiation field (ISRF). High-galactic-latitudes dark nebulae are seen as bright nebulae when surrounded by transparent areas which have less scattered light from the general galactic dust layer. Aims. Photometry of the bright dark nebulae LDN 1780, LDN 1642, and LBN 406 shall be used to derive scattering properties of dust and to investigate the presence of UV fluorescence emission by molecular hydrogen and the extended red emission (ERE). Methods. We used multi-wavelength optical photometry and imaging at ground-based telescopes and archival imaging and spectroscopic UV data from the spaceborn GALEX and SPEAR/FIMS instruments. In the analysis we used Monte Carlo RT and both observational data and synthetic models for the ISRF in the solar neighbourhood. The line-of-sight extinctions through the clouds have been determined using near infrared excesses of background stars and the 200/250 μm far infrared emission by dust as measured using the ISO and Herschel space observatories. Results. The optical surface brightness of the three target clouds can be explained in terms of scattered light. The dust albedo ranges from ~0.58 at 3500 Å to ~0.72 at 7500 Å. The spectral energy distribution of LDN 1780 is explained in terms of optical depth and background scattered light effects instead of the original published suggestion in terms of ERE. The far-ultraviolet surface brightness of LDN 1780 cannot be explained by scattered light only. In LDN 1780, H2 fluorescent emission in the wavelength range 1400–1700 Å has been detected and analysed. Conclusions. Our albedo values are in good agreement with the predictions of the dust model of Weingartner and Draine and with the THEMIS CMM model for evolved core-mantle grains. The distribution of H2 fluorescent emission in LDN 1780 shows a pronounced dichotomy with a strong preference for its southern side where enhanced illumination is impinging from the Sco OB2 association and the O star ζ Oph. A good correlation is found between the H2 fluorescence and a previously mapped 21-cm excess emission. The H2 fluorescence emission in LDN 1780 has been modelled using a PDR code; the resulting values for H2 column density and the total gas density are consistent with the estimates derived from CO observations and optical extinction along the line of sight.

Heat Generation in Laser Irradiated Tissue

1989 ◽  
Vol 111 (1) ◽  
pp. 62-68 ◽  
Author(s):  
A. J. Welch ◽  
J. A. Pearce ◽  
K. R. Diller ◽  
G. Yoon ◽  
W. F. Cheong
Keyword(s):  
Heat Source ◽  
Heat Generation ◽  
Near Infrared ◽  
Scattered Light ◽  
Incident Beam ◽  
Accurate Estimation ◽  
Optical Parameters ◽  
Infrared Wavelengths ◽  
Improved Model

Many medical applications involving lasers rely upon the generation of heat within the tissue for the desired therapeutic effect. Determination of the absorbed light energy in tissue is difficult in many cases. Although UV wavelengths of the excimer laser and 10.6 μm wavelength of the CO2 laser are absorbed within the first 20 μm of soft tissue, visible and near infrared wavelengths are scattered as well as absorbed. Typically, multiple scattering is a significant factor in the distribution of light in tissue and the resulting heat source term. An improved model is presented for estimating heat generation due to the absorption of a collimated (axisymmetric) laser beam and scattered light at each point r and z in tissue. Heat generated within tissue is a function of the laser power, the shape and size of the incident beam and the optical properties of the tissue at the irradiation wavelength. Key to the calculation of heat source strength is accurate estimation of the light distribution. Methods for experimentally determining the optical parameters of tissue are discussed in the context of the improved model.

scholarly journals New disk discovered with VLT/SPHERE around the M star GSC 07396−00759

2018 ◽  
Vol 613 ◽  
pp. L6 ◽  
Author(s):  
E. Sissa ◽  
J. Olofsson ◽  
A. Vigan ◽  
J. C. Augereau ◽  
V. D’Orazi ◽  
...  
Keyword(s):  
Near Infrared ◽  
Scattered Light ◽  
Debris Disks ◽  
M Dwarfs ◽  
Infrared Excess ◽  
Asymmetric Structures ◽  
High Resolution Imagery ◽  
Low Mass ◽  
Dust Dynamics ◽  
M Dwarf

Debris disks are usually detected through the infrared excess over the photospheric level of their host star. The most favorable stars for disk detection are those with spectral types between A and K, while the statistics for debris disks detected around low-mass M-type stars is very low, either because they are rare or because they are more difficult to detect. Terrestrial planets, on the other hand, may be common around M-type stars. Here, we report on the discovery of an extended (likely) debris disk around the M-dwarf GSC 07396−00759. The star is a wide companion of the close accreting binary V4046 Sgr. The system probably is a member of the β Pictoris Moving Group. We resolve the disk in scattered light, exploiting high-contrast, high-resolution imagery with the two near-infrared subsystems of the VLT/SPHERE instrument, operating in the Y J bands and the H2H3 doublet. The disk is clearly detected up to 1.5′′ (~110 au) from the star and appears as a ring, with an inclination i ~ 83°, and a peak density position at ~70 au. The spatial extension of the disk suggests that the dust dynamics is affected by a strong stellar wind, showing similarities with the AU Mic system that has also been resolved with SPHERE. The images show faint asymmetric structures at the widest separation in the northwest side. We also set an upper limit for the presence of giant planets to 2 MJ. Finally, we note that the 2 resolved disks around M-type stars of 30 such stars observed with SPHERE are viewed close to edge-on, suggesting that a significant population of debris disks around M dwarfs could remain undetected because of an unfavorable orientation.

scholarly journals High-resolution mapping of interstellar clouds with near-infrared scattered light

2006 ◽  
Vol 2 (S237) ◽  
pp. 430-430
Author(s):  
M. Juvela ◽  
V.-M. Pelkonen ◽  
P. Padoan ◽  
K. Mattila
Keyword(s):  
Column Density ◽  
Surface Brightness ◽  
Near Infrared ◽  
Scattered Light ◽  
Interstellar Clouds ◽  
Nir Light ◽  
High Resolution Mapping ◽  
Colour Excess ◽  
Resolution Mapping ◽  
Transfer Modelling

AbstractWe examine the intensity of scattered near-infrared (NIR) light in the case of interstellar clouds illuminated by the normal interstellar radiation field. We have developed a way to convert the observed surface brightness into estimates of the column density and have estimated the accuracy of the new method. The NIR intensities can be converted into reliable estimates of the column density in regions with AV up to almost 20 magnitudes. The errors can be further reduced with detailed radiative transfer modelling and by using the lower resolution information that is provided by the colour excess data of background stars. Therefore, NIR scattered light is a promising new way to map quiescent interstellar clouds at a high, even sub-arcsecond resolution.

scholarly journals Scaling relations of early-type galaxies in the 6dF Galaxy Survey

2009 ◽  
Vol 5 (H15) ◽  
pp. 84-84
Author(s):  
C. Magoulas ◽  
M. Colless ◽  
H. Jones ◽  
J. Mould ◽  
C. Springob
Keyword(s):  
Surface Brightness ◽  
Near Infrared ◽  
Velocity Dispersion ◽  
Three Dimensional ◽  
Gaussian Model ◽  
Early Type ◽  
Fundamental Plane ◽  
Infrared Wavelengths ◽  
Observational Errors ◽  
Intrinsic Scatter

Over 10,000 early-type galaxies from the 6dF Galaxy Survey (6dFGS) (Jones, D. H. et al. (2009), Jones et al. (2004)) have been used to determine the Fundamental Plane at optical and near-infrared wavelengths. We find that a maximum likelihood fit to an explicit three-dimensional Gaussian model for the distribution of galaxies in size, surface brightness and velocity dispersion can precisely account for selection effects, censoring and observational errors, leading to precise and unbiased parameters for the Fundamental Plane and its intrinsic scatter.

scholarly journals A Comparative Anatomy of Dusty Disks Imaged by NICMOS

2004 ◽  
Vol 202 ◽  
pp. 308-315
Author(s):  
Glenn Schneider ◽  
Dean C. Hines ◽  
Murray Silverstone ◽  
Alycia J. Weinberger ◽  
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Comparative Anatomy ◽  
Scattered Light ◽  
Infrared Camera ◽  
Main Sequence Stars ◽  
Spatially Resolved ◽  
T Tauri ◽  
Dusty Disks

Using the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope we have conducted a coronagraphic imaging survey of 18 main sequence stars with large infrared excesses, searching for circumstellar dust (debris) in scattered light. Dusty disks with radial and hemispheric brightness anisotropies and complex morphologies, both possibly indicative of dynamical interactions with unseen planetary mass companions, were spatially resolved and imaged around three young (≲ 10Myr old) stars. From these observations we describe the debris systems around: a) HR 4796A (A0V), a 70 AU radius ring less than 14 AU wide with unequal ansal flux densities; b) HD 141569A (Herbig Ae/Be), a 400 AU radius disk with a 40 AU wide gap; and c) TW Hya (K7 T-Tauri), a pole-on circularly symmetric disk with a radial break in its surface density of scattering particles. Additionally, our non-detection of scattered light and high precision photometry of a fourth system of similar age, HD 98800 A/B, coupled with mid and thermal IR measurements, greatly constrain a likely model for the debris about the B component.

scholarly journals Surface waves in protoplanetary disks induced by outbursts: Concentric rings in scattered light

2018 ◽  
Vol 617 ◽  
pp. L7
Author(s):  
A. D. Schneider ◽  
C. P. Dullemond ◽  
B. Bitsch
Keyword(s):  
Radiative Transfer ◽  
Surface Waves ◽  
Vertical Structure ◽  
Near Infrared ◽  
Scattered Light ◽  
Protoplanetary Disks ◽  
Protoplanetary Disk ◽  
Diffusion Method ◽  
Disk Structure ◽  
Infrared Wavelengths

Context. Vertically hydrostatic protoplanetary disk models are based on the assumption that the main heating source, stellar irradiation, does not vary much with time. However, it is known that accreting young stars are variable sources of radiation. This is particularly evident for outbursting sources such as EX Lupi and FU Orionis stars. Aims. We investigate how such outbursts affect the vertical structure of the outer regions of the protoplanetary disk, in particular their appearance in scattered light at optical and near-infrared wavelengths. Methods. We employ the 3D FARGOCA radiation-hydrodynamics code, in polar coordinates, to compute the time-dependent behavior of the axisymmetric disk structure. The temperature is computed self-consistently and time-dependently from the irradiation flux using a two-stage radiative transfer method: first the direct illumination is computed; then the diffuse radiation is treated with the flux-limited diffusion method. The outbursting inner disk region is not included explicitly. Instead, its luminosity is added to the stellar luminosity and is thus included in the irradiation of the outer disk regions. For time snapshots of interest we insert the density structure into the RADMC-3D radiative transfer code and compute the appearance of the disk at optical/near-infrared wavelengths, where we observe stellar light that is scattered off the surface of the disk. Results. We find that, depending on the amplitude of the outbursts, the vertical structure of the disk can become highly dynamic, featuring circular surface waves of considerable amplitude. These “hills” and “valleys” on the disk’s surface show up in the scattered light images as bright and dark concentric rings. Initially these rings are small and act as standing waves, but they subsequently lead to outward propagating waves, like the waves produced by a stone thrown into a pond. These waves continue long after the actual outburst has died out. Conclusions. Single, periodic, or quasiperiodic outbursts of the innermost regions of protoplanetary disks will necessarily lead to wavy structures on the surface of these disks at all radii. We propose that some of the multi-ringed structures seen in optical/infrared images of several protoplanetary disks may have their origin in outbursts that occurred decades or centuries ago. However, the multiple rings seen at (sub-)millimeter wavelengths in HL Tau and several other disks are not expected to be related to such waves.

scholarly journals Polarimetric and radiative transfer modelling of HD 172555

2020 ◽  
Vol 499 (4) ◽  
pp. 5915-5931
Author(s):  
Jonathan P Marshall ◽  
Daniel V Cotton ◽  
Peter Scicluna ◽  
Jeremy Bailey ◽  
Lucyna Kedziora-Chudczer ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Near Infrared ◽  
Scattered Light ◽  
Position Angle ◽  
Polarization Measurement ◽  
Continuum Emission ◽  
Dust Grains ◽  
Spatially Resolved ◽  
Optical Aperture ◽  
Transfer Modelling

ABSTRACT The debris disc around HD 172555 was recently imaged in near-infrared polarized scattered light by the Very Large Telescope’s Spectro-Polarimetric High-contrast Exoplanet REsearch instrument. Here we present optical aperture polarization measurements of HD 172555 by the HIgh Precision Polarimetric Instrument (HIPPI), and its successor HIPPI-2 on the Anglo-Australian Telescope. We seek to refine constraints on the disc’s constituent dust grains by combining our polarimetric measurements with available infrared and millimetre photometry to model the scattered light and continuum emission from the disc. We model the disc using the 3D radiative transfer code hyperion, assuming the orientation and extent of the disc as obtained from the SPHERE observation. After correction for the interstellar medium contribution, our multiwavelength HIPPI/-2 observations (both magnitude and orientation) are consistent with the recent SPHERE polarization measurement with a fractional polarization p = 62.4  ±  5.2 ppm at 722.3 nm, and a position angle θ = 67°  ±  3°. The multiwavelength polarization can be adequately replicated by compact, spherical dust grains (i.e. from Mie theory) that are around 1.2 μm in size, assuming astronomical silicate composition, or 3.9 μm, assuming a composition derived from radiative transfer modelling of the disc. We were thus able to reproduce both the spatially resolved disc emission and polarization with a single grain composition model and size distribution.

scholarly journals Time Variation of the Solar Dust Cloud

1996 ◽  
Vol 150 ◽  
pp. 353-356 ◽  
Author(s):  
H. Kimura
Keyword(s):  
Temporal Variation ◽  
Size Distribution ◽  
Near Infrared ◽  
Thermal Emission ◽  
Scattered Light ◽  
Dust Cloud ◽  
Line Of Sight ◽  
Dust Grains ◽  
Infrared Wavelengths ◽  
Potential Origin

AbstractWe have found from line-of-sight integration of scattered light and thermal emission that the appearance of a hump in the F-corona, which was observed in the near-infrared wavelengths by Peterson (1969) and MacQueen (1968), is very sensitive to the change of size distribution of circumsolar dust grains. Namely, the size distribution affects the balance of scattered sunlight and thermal emission. We suggest that a temporal variation in the size distribution of circumsolar dust grains is a potential origin of the temporal variation of the hump structure observed in the F-corona.

Sign in / Sign up

Export Citation Format

Share Document