The near-infrared continuum emission of visual reflection nebulae

1984 ◽  
Vol 277 ◽  
pp. 623 ◽  
Author(s):  
K. Sellgren
Keyword(s):  
Near Infrared ◽  
Continuum Emission ◽  
Infrared Continuum ◽  
Reflection Nebulae

scholarly journals Principal component analysis tomography in near-infrared integral field spectroscopy of young stellar objects – I. Revisiting the high-mass protostar W33A

2021 ◽  
Vol 503 (1) ◽  
pp. 270-291
Author(s):  
F Navarete ◽  
A Damineli ◽  
J E Steiner ◽  
R D Blum
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Rotation Axis ◽  
Principal Component ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
Rotating Disc ◽  
Stellar Objects ◽  
K Band

ABSTRACT W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the K-band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position–velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0.1 arcsec (∼250 au) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0$^{+4.1}_{-2.2}$ $\rm {M}_\odot$ for the ‘disc + protostar’ system, about ∼33 per cent smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H2 wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of ∼63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of ∼7000 au from W33A, powering extended K-band continuum emission detected in the same field. Another source (Source C) is driving a bipolar $\rm {H}_2$ jet aligned perpendicular to the rotation axis of W33A.

scholarly journals High gas-to-dust size ratio indicating efficient radial drift in the mm-faint CX Tauri disk

2019 ◽  
Vol 626 ◽  
pp. L2 ◽  
Author(s):  
S. Facchini ◽  
E. F. van Dishoeck ◽  
C. F. Manara ◽  
M. Tazzari ◽  
L. Maud ◽  
...  
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
Spectral Energy Distribution ◽  
Theoretical Models ◽  
Intensity Profile ◽  
Continuum Emission ◽  
Spectral Energy ◽  
High Angular Resolution ◽  
Sharp Drop ◽  
Large Program

The large majority of protoplanetary disks have very compact continuum emission (≲15 AU) at millimeter wavelengths. However, high angular resolution observations that resolve these small disks are still lacking, due to their intrinsically fainter emission compared with large bright disks. In this Letter we present 1.3 mm ALMA data of the faint disk (∼10 mJy) orbiting the TTauri star CX Tau at a resolution of ∼40 mas, ∼5 AU in diameter. The millimeter dust disk is compact, with a 68% enclosing flux radius of 14 AU, and the intensity profile exhibits a sharp drop between 10 and 20 AU, and a shallow tail between 20 and 40 AU. No clear signatures of substructure in the dust continuum are observed, down to the same sensitivity level of the DSHARP large program. However, the angular resolution does not allow us to detect substructures on the scale of the disk aspect ratio in the inner regions. The radial intensity profile closely resembles the inner regions of more extended disks imaged at the same resolution in DSHARP, but with no rings present in the outer disk. No inner cavity is detected, even though the disk has been classified as a transition disk from the spectral energy distribution in the near-infrared. The emission of 12CO is much more extended, with a 68% enclosing flux radius of 75 AU. The large difference of the millimeter dust and gas extents (> 5) strongly points to radial drift, and closely matches the predictions of theoretical models.

scholarly journals The Origin of Continuum Emission in Active Galactic Nuclei

1994 ◽  
Vol 159 ◽  
pp. 5-16 ◽  
Author(s):  
Joel N. Bregman
Keyword(s):  
Accretion Disk ◽  
Near Infrared ◽  
Galactic Nuclei ◽  
Black Body ◽  
Continuum Emission ◽  
Radiation Mechanism ◽  
X Ray ◽  
Pair Plasma ◽  
Inverse Compton ◽  
The Continuum

The general understanding of the continuum emission from AGN has changed from the picture where nonthermal processes were responsible for all of the emission. The current body of observation indicates that there are two types of objects, one being the blazar class (or blazar component), where nearly all of the emission is nonthermal, due primarily to synchrotron and inverse Compton emission. Variability studies indicate that the emitting region decreases with size from the radio through the X-ray region, where the size of the X-ray region is of order a light hour. More than two dozen of these radio-loud AGNs have been detected at GeV energies (one source at TeV energies), for which the radiation mechanism may be inverse Compton mechanism.In the other class, the radio-quiet AGN (component), the emission is almost entirely thermal, with radiation from dust dominating the near infrared to submillimeter region. The optical to soft X-ray emission is often ascribed to black body emission from an opaque accretion disk, but variability studies may not be consistent with expectations. Another attractive model has free-free emission being responsible for the optical to soft X-ray emission. The highest frequencies at which these AGN are detected is the MeV range, and these data should help to determine if this emission is produced in a scattering atmosphere, such as that around an accretion disk, or by another model involving an opaque pair plasma.

scholarly journals A Search for Disks around Massive Young Stellar Objects

2004 ◽  
Vol 221 ◽  
pp. 425-430 ◽  
Author(s):  
A. G. Gibb ◽  
M. G. Hoare ◽  
L. G. Mundy ◽  
F. Wyrowski
Keyword(s):  
Near Infrared ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Circumstellar Disk ◽  
Mass Yield ◽  
Stellar Objects ◽  
Strong Emission ◽  
Yield Values ◽  
Infrared Data ◽  
The Continuum

We present subarcsecond observations at 2.7 and 1.4 mm of a sample of massive young stellar objects made with the BIMA millimetre array. For most sources the continuum emission on the smallest scales at 2.7 mm is dominated by free-free emission from the stellar wind or jet. Strong emission at 1.4 mm shows the presence of significant dust associated with Cep A and GL 490 but our resolution is not sufficient to resolve any structure. The 2.7-mm emission from GL 490 is resolved but it is not clear whether we are seeing a single circumstellar disk or a secondary companion, although near-infrared data support the disk hypothesis. Estimates of the dust mass yield values of ∼1–4 M⊙ within radii of 150 to 1000 AU.

scholarly journals Near-infrared monitoring of the accretion outburst in the massive young stellar object S255-NIRS3

2019 ◽  
Vol 72 (1) ◽  
Author(s):  
Mizuho Uchiyama ◽  
Takuya Yamashita ◽  
Koichiro Sugiyama ◽  
Tatsuya Nakaoka ◽  
Miho Kawabata ◽  
...  
Keyword(s):  
Light Curve ◽  
Near Infrared ◽  
Stellar Object ◽  
Young Stellar Objects ◽  
Infrared Light ◽  
Continuum Emission ◽  
Sudden Increase ◽  
Maser Emission ◽  
Young Stellar Object ◽  
Band Emission

Abstract We followed up the massive young stellar object S255-NIRS3 (= S255-IRS1b) during its recent accretion outburst event in the $K_{\rm s}$ band with Kanata/HONIR for four years after its burst and obtained a long-term light curve. This is the most complete near-infrared light curve of the S255-NIRS3 burst event that has ever been presented. The light curve showed a steep increase reaching a peak flux that was 3.4 mag brighter than the quiescent phase and then a relatively moderate year-scale fading until the last observation, similar to that of the accretion burst events such as EXors found in lower-mass young stellar objects. The behavior of the $K_{\rm s}$-band light curve is similar to that observed in 6.7 GHz class II methanol maser emission, with a sudden increase followed by moderate year-scale fading. However, the maser emission peaks appear 30–50 d earlier than that of the $K_{\rm s}$ band emission. The similarities confirmed that the origins of the maser emission and the $K_{\rm s}$-band continuum emission are common, as previously shown from other infrared and radio observations by Stecklum et al. (2016, Astronomer’s Telegram, 8732), Caratti o Garatti et al. (2017b, Nature Phys., 13, 276), and Moscadelli et al. (2017, A&A, 600, L8). However, the differences in energy transfer paths, such as the exciting/emitting/scattering structures, may cause the delay in the flux-peak dates.

scholarly journals Nature of the Dusty S-cluster Object (DSO/G2): Pre-main-sequence star with non-spherical dusty envelope

2016 ◽  
Vol 11 (S322) ◽  
pp. 231-232
Author(s):  
M. Zajaček ◽  
M. Valencia-S. ◽  
B. Shahzamanian ◽  
F. Peissker ◽  
A. Eckart ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Main Sequence ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Main Sequence Star ◽  
Continuum Emission ◽  
Spectral Energy ◽  
Galactic Centre ◽  
Infrared Excess ◽  
Sgr A

AbstractNear-infrared observations reveal several infrared-excess sources near the Galactic Centre with emission lines present in their spectra. One of these objects, DSO/G2, which moves around the supermassive black hole (Sgr A*) on a highly eccentric orbit, passed the pericentre at approximately 160 AU in 2014. It remained compact, which implies that at least in this case it is a star embedded in a dusty envelope. The spectral energy distribution and the detection of polarized continuum emission indicate that it is probably a pre-main-sequence star surrounded by a dense envelope with bipolar cavities. In addition, the star associated with DSO/G2 plausibly develops a bow shock due to its supersonic motion. The model of the star surrounded by the non-spherical dusty envelope can reproduce the main characteristics of the DSO/G2 source: 1. spectral energy distribution in near-infrared bands; 2. linear polarization in Ks band; and 3. the overall compact behaviour.

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