scholarly journals Modeling the Unresolved NIR–MIR SEDs of Local (z < 0.1) QSOs

2021 ◽  
Vol 922 (2) ◽  
pp. 157
Author(s):  
M. Martínez-Paredes ◽  
O. González-Martín ◽  
K. HyeongHan ◽  
S. Geier ◽  
I. García-Bernete ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Near Infrared ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Two Phase ◽  
Stellar Objects ◽  
Mid Infrared ◽  
Disk Wind ◽  
Quasi Stellar Objects ◽  
Nir Emission

Abstract To study the nuclear (≲1 kpc) dust of nearby (z < 0.1) quasi-stellar objects (QSOs), we obtained new near-infrared (NIR) high angular resolution (∼0.″3) photometry in the H and Ks bands for 13 QSOs with available mid-infrared (MIR) high angular resolution spectroscopy (∼7.5–13.5 μm). We find that in most QSOs, the NIR emission is unresolved. We subtract the contribution from the accretion disk, which decreases from NIR (∼35%) to MIR (∼2.4%). We also estimate these percentages assuming a bluer accretion disk and find that the contribution in the MIR is nearly seven times larger. We find that the majority of objects (64%, 9/13) are better fitted by the disk+wind H17 model, while others can be fitted by the smooth F06 (14%, 2/13), clumpy N08 (7%, 1/13), clumpy H10 (7%, 1/13), and two-phase media S16 (7%, 1/13) models. However, if we assume the bluer accretion disk, the models fit only 2/13 objects. We measured two NIR-to-MIR spectral indexes, α NIR−MIR(1.6–8.7 μm) and α NIR−MIR(2.2–8.7 μm), and two MIR spectral indexes, α MIR(7.8–9.8 μm) and α MIR(9.8–11.7 μm), from models and observations. From observations, we find that the NIR-to-MIR spectral indexes are ∼−1.1, and the MIR spectral indexes are ∼−0.3. Comparing the synthetic and observed values, we find that none of the models simultaneously match the measured NIR-to-MIR and 7.8–9.8 μm slopes. However, we note that measuring α MIR(7.8–9.8 μm) on the starburst-subtracted Spitzer/IRS spectrum gives values of the slopes (∼−2) that are similar to the synthetic values obtained from the models.

scholarly journals High Angular Resolution Observations of Protostellar Disks

1994 ◽  
Vol 158 ◽  
pp. 387-390
Author(s):  
J.-L. Monin ◽  
J. Bouvier ◽  
F. Malbet
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
Circumstellar Disks ◽  
Physical Structure ◽  
Young Stellar Objects ◽  
High Angular Resolution ◽  
Stellar Objects ◽  
Star Forming ◽  
T Tauri ◽  
Chromatic Properties

The existence of circumstellar disks around young stellar objects like T Tauri stars is now well accepted. Such disks would have solar system sizes and, at the distance of the nearest star forming cloud, an angular diameter of 0.01 to 1 arcsecond at most, requiring very high angular resolution to be detected. Due to the nature of the emission process in circumstellar disks and to chromatic properties of ground based observations, disk imaging is expected to be more efficient in the near infrared. Also, multi-aperture interferometry in this wavelength range (1 – 10 μm) is expected to bring considerable insight into the disks properties and evolution in revealing their inner physical structure.In this paper, we present synthetic images of circumstellar accretion disks. The images have been computed from a complete disk vertical structure model.

scholarly journals Influence of the input-stage architecture on the in-laboratory test of a mid-infrared interferometer: application to the ALOHA up-conversion interferometer in the L band

2020 ◽  
Vol 501 (1) ◽  
pp. 531-540
Author(s):  
Julie Magri ◽  
Lucien Lehmann ◽  
Ludovic Grossard ◽  
Laurent Delage ◽  
François Reynaud ◽  
...  
Keyword(s):  
Laboratory Test ◽  
Near Infrared ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
High Flux ◽  
Hybrid Analysis ◽  
Mid Infrared ◽  
Input Stage ◽  
L Band ◽  
Set Up

ABSTRACT In the framework of the Astronomical Light Optical Hybrid Analysis (ALOHA) laboratory mid-infrared (MIR) up-conversion fibred interferometer in the L band, we report on the influence of the input-stage architecture. Using an amplitude division set-up in the visible or near-infrared is a straightforward choice in most cases. In the MIR context, the results are slightly different and we show that a wavefront division set-up is needed. These in-laboratory principle experiments allow us to measure a reliable 88 per cent instrumental contrast with high flux and to obtain fringes from faint sources at 3.5 μm with a spectral bandwith of 37 nm converted to 817 nm. An equivalent limiting L-band magnitude around 3.9, equivalent to 3.0 fW nm−1, could be demonstrated on 1 m class telescopes. This opens the possibility of planning future on-sky tests at the Center for High Angular Resolution Astronomy (CHARA) array and of predicting the performance attained.

Zooming into the complex dusty envelopes of C-rich AGB stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 456-457
Author(s):  
Foteini Lykou ◽  
Josef Hron ◽  
Daniela Klotz
Keyword(s):  
Temperature Distribution ◽  
Near Infrared ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Dust Formation ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Recent Advances ◽  
Multi Wavelength

AbstractRecent advances in high-angular resolution instruments (VLT and VLTI, ALMA) have enabled us to delve deep into the circumstellar envelopes of AGB stars from the optical to the sub-mm wavelengths, thus allowing us to study in detail the gas and dust formation zones (e.g., their geometry, chemistry and kinematics). This work focuses on four (4) C-rich AGB stars observed with a high-angular resolution technique in the near-infrared: a multi-wavelength tomographic study of the dusty layers of the circumstellar envelopes of these C-rich stars, i.e. the variations in the morphology and temperature distribution.

scholarly journals THE HIGH A V Quasar Survey: Reddened Quasi-Stellar Objects selected from optical/near-infrared photometry. II.

2015 ◽  
Vol 217 (1) ◽  
pp. 5 ◽  
Author(s):  
J.-K. Krogager ◽  
S. Geier ◽  
J. P. U. Fynbo ◽  
B. P. Venemans ◽  
C. Ledoux ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Photometry ◽  
Stellar Objects ◽  
Quasi Stellar Objects

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 complex evolutionary paths of local infrared bright galaxies: a high-angular resolution mid-infrared view

2016 ◽  
Vol 463 (3) ◽  
pp. 2405-2424 ◽  
Author(s):  
A. Alonso-Herrero ◽  
R. Poulton ◽  
P. F. Roche ◽  
A. Hernán-Caballero ◽  
I. Aretxaga ◽  
...  
Keyword(s):  
Angular Resolution ◽  
High Angular Resolution ◽  
Mid Infrared ◽  
Evolutionary Paths

scholarly journals Quasi-stellar object redshift estimates from optical, near-infrared, and ultraviolet colours

2019 ◽  
Vol 629 ◽  
pp. A56 ◽  
Author(s):  
S. J. Curran ◽  
J. P. Moss
Keyword(s):  
Active Galactic Nuclei ◽  
Rest Frame ◽  
Near Infrared ◽  
Galactic Nuclei ◽  
Additional Contribution ◽  
Stellar Objects ◽  
Simple Estimate ◽  
Photometric Redshift ◽  
Wide Range ◽  
Quasi Stellar Objects

A simple estimate of the photometric redshift would prove invaluable to forthcoming continuum surveys on the next generation of large radio telescopes, as well as mitigating the existing bias towards the most optically bright sources. While there is a well-known correlation between the near-infrared K-band magnitude and redshift for galaxies, we find the K − z relation to break down for samples dominated by quasi-stellar objects. We hypothesise that this is due to the additional contribution to the near-infrared flux by the active galactic nucleus, and, as such, the K-band magnitude can only provide a lower limit to the redshift in the case of active galactic nuclei, which will dominate the radio surveys. From a large optical dataset, we find a tight relationship between the rest-frame (U − K)/(W2 − FUV) colour ratio and spectroscopic redshift over a sample of 17 000 sources, spanning z ≈ 0.1−5. Using the observed-frame ratios of (U − K)/(W2 − FUV) for redshifts of z ≲ 1, (I − W2)/(W3 − U) for 1 ≲ z ≲ 3, and (I − W2.5)/(W4 − R) for z ≳ 3, where W2.5 is the λ = 8.0 μm magnitude and the appropriate redshift ranges are estimated from the W2 (4.5 μm) magnitude, we find this to be a robust photometric redshift estimator for quasars. We suggest that the rest-frame U − K colour traces the excess flux from the AGN over this wide range of redshifts, although the W2 − FUV colour is required to break the degeneracy.

Near Infrared High Angular Resolution Observations of Stars and Circumstellar Regions by the Technique of Lunar Occultations

1994 ◽  
Vol 158 ◽  
pp. 376-378
Author(s):  
T. Chandrasekhar ◽  
N. M. Ashok ◽  
Sam Ragland
Keyword(s):  
High Speed ◽  
Near Infrared ◽  
Angular Resolution ◽  
Infrared Region ◽  
High Angular Resolution ◽  
Filter Bandwidth ◽  
One Dimensional ◽  
Near Infrared Region ◽  
System Frequency ◽  
Source Structure

A program of High Angular Resolution observations of stars and their circumstellar regions using the technique of lunar occultations has been initiated at the 1.2 m telescope at Gurushikhar (24°39′ N, 72°47′ E), India. A liquid nitrogen cooled InSb detector based high speed Infrared photometer with millisecond data acquisition capabilities has been developed for the near Infrared region (1–5 μm) and eight occultations have been successfully observed in the K band (2.2 μm). The sources are (IRC No. -10578, +10013, +20034, +30094, +20190, +20200, +20073 and +00198. The diffraction pattern is clearly seen in all the observations. A convolution analysis involving the system frequency response, filter bandwidth and one dimensional source structure has been carried out to fit the data. System capability has been determined to be ~ 6 milliarcseconds.

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