scholarly journals The infrared view of dust and molecules around V4334 Sgr (Sakurai’s object): a 20-yr retrospective

2020 ◽  
Vol 493 (1) ◽  
pp. 1277-1291 ◽  
Author(s):  
A Evans ◽  
R D Gehrz ◽  
C E Woodward ◽  
D P K Banerjee ◽  
T R Geballe ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Near Infrared ◽  
Dust Emission ◽  
Infrared Excess ◽  
Object A ◽  
Bolometric Luminosity ◽  
Dust Mass ◽  
Mass Ejection ◽  
Lower Limits ◽  
Hydrogenated Amorphous

ABSTRACT We present an analysis of the evolution of circumstellar dust and molecules in the environment of the very late thermal pulse object V4334 Sgr (Sakurai’s object) over an ∼20-yr period, drawing on ground-, airborne-, and space-based infrared photometry and spectroscopy. The dust emission, which started in 1997, resembles a blackbody that cooled from ∼1200 K in 1998 August to ∼180 K in 2016 July. The dust mass, assuming amorphous carbon, was ∼5 × 10−10 M⊙ in 1998 August, and we estimate that the total dust mass was ∼2 × 10−5 M⊙ by ∼2016. The appearance of a near-infrared excess in 2008 suggests that a new episode of (or renewed) mass-loss began then. We infer lower limits on the bolometric luminosity of the embedded star from that of the dust shell, which rose to ∼16 000 L⊙ before declining to ∼3000 L⊙. There is evidence for weak 6–7 μm absorption, which we attribute to hydrogenated amorphous carbon formed in material ejected by Sakurai’s object during a mass ejection phase that preceded the 1997 event. We detect small hydrocarbon and other molecules in the spectra, and trace the column densities in hydrogen cyanide (HCN) and acetylene (C2H2). We use the former to determine the 12C/13C ratio to be 6.4 ± 0.7, 14 times smaller than the Solar system value.

scholarly journals A Gas and Dust Rich Giant Elliptical Galaxy

2005 ◽  
Vol 13 ◽  
pp. 872-874
Author(s):  
O. Krause ◽  
U. Lisenfeld ◽  
U. Klaas ◽  
D. Lemke ◽  
M. Haas ◽  
...  
Keyword(s):  
Elliptical Galaxy ◽  
Dust Emission ◽  
Optical Spectra ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Bolometric Luminosity ◽  
Thermal Radio ◽  
Visual Extinction ◽  
Dust Mass ◽  
Ir Emission

AbstractThe bolometric luminosity of LFIR = 2×1012 L⊙ makes ISOSS J 15079+7247 one of the most luminous and unusual galaxies detected by the 170 μm ISOPHOT Serendipity Survey (ISOSS). The detection of CO (1-0) emission identifies a giant elliptical galaxy at redshift z = 0.2136 as the counterpart of the FIR source. The derived high gas mass of 3 × 1010 M⊙ favours the picture that the dust emission is associated with this elliptical galaxy. The ultraluminous IR emission can be explained by a hidden starburst in the center of the elliptical. This is supported by the strength of non-thermal radio continuum emission. The huge dust mass of 5×108 M⊙ corresponds to a visual extinction of AV ~ 1000 mag, being consistent with the non-detection of any signatures of a strong starburst in ISOSS J 15079+7247 in optical spectra.

scholarly journals The dust content of the Crab Nebula

2019 ◽  
Vol 488 (1) ◽  
pp. 164-182 ◽  
Author(s):  
I De Looze ◽  
M J Barlow ◽  
R Bandiera ◽  
A Bevan ◽  
M F Bietenholz ◽  
...  
Keyword(s):  
Spectral Index ◽  
Near Infrared ◽  
Crab Nebula ◽  
Dust Emission ◽  
Infrared Emission ◽  
Small Contribution ◽  
Dust Extinction ◽  
Dust Mass ◽  
The Crab Nebula ◽  
Dust Condensation

ABSTRACT We have modelled the near-infrared to radio images of the Crab Nebula with a Bayesian SED model to simultaneously fit its synchrotron, interstellar (IS), and supernova dust emission. We infer an IS dust extinction map with an average AV = 1.08 ± 0.38 mag, consistent with a small contribution (${\lesssim }22{{\ \rm per\ cent}}$) to the Crab’s overall infrared emission. The Crab’s supernova dust mass is estimated to be between 0.032 and 0.049 M⊙ (for amorphous carbon grains) with an average dust temperature Tdust = 41 ± 3 K, corresponding to a dust condensation efficiency of 8–12 ${{\ \rm per\ cent}}$. This revised dust mass is up to an order of magnitude lower than some previous estimates, which can be attributed to our different IS dust corrections, lower SPIRE flux densities, and higher dust temperatures than were used in previous studies. The dust within the Crab is predominantly found in dense filaments south of the pulsar, with an average V-band dust extinction of AV = 0.20–0.39 mag, consistent with recent optical dust extinction studies. The modelled synchrotron power-law spectrum is consistent with a radio spectral index αradio = 0.297 ± 0.009 and an infrared spectral index αIR = 0.429 ± 0.021. We have identified a millimetre excess emission in the Crab’s central regions, and argue that it most likely results from two distinct populations of synchrotron emitting particles. We conclude that the Crab’s efficient dust condensation (8–12 ${{\ \rm per\ cent}}$) provides further evidence for a scenario where supernovae can provide substantial contributions to the IS dust budgets in galaxies.

scholarly journals New evidence for the ubiquity of prominent polar dust emission in AGN on tens of parsec scales

2019 ◽  
Vol 489 (2) ◽  
pp. 2177-2188 ◽  
Author(s):  
D Asmus
Keyword(s):  
Active Galactic Nuclei ◽  
Dust Emission ◽  
Galactic Nuclei ◽  
Large Telescope ◽  
Mid Infrared ◽  
Bolometric Luminosity ◽  
Very Large Telescope ◽  
Lower Limits ◽  
New Evidence ◽  
Small Dispersion

ABSTRACT The key ingredient of active galactic nuclei (AGN) unification, the dusty obscuring torus was so far held responsible for the observed mid-infrared (MIR) emission of AGN. However, the best studied objects with Very Large Telescope Interferometer (VLTI)/MID-infrared Interferometric instrument (MIDI) show that instead a polar dusty wind is dominating these wavelengths, leaving little room for a torus contribution. But is this wind a ubiquitous part of the AGN? To test this, we conducted a straightforward detection experiment, using the upgraded Very Large Telescope (VLT)/VLT Imager and Spectrometer for mid-InfraRed (VISIR) for deep subarcsecond resolution MIR imaging of a sample of nine [O iv]-bright, obscured AGN, all of which were predicted to have detectable polar emission. Indeed, the new data reveal such emission in all objects but one. We further estimate lower limits on the extent of the polar dust and show that the polar dust emission is dominating the total MIR emission of the AGN. These findings support the scenario that polar dust is not only ubiquitous in AGN but also an integral part of its structure, processing a significant part of the primary radiation. The polar dust has to be optically thin on average, which explains e.g. the small dispersion in the observed MIR–X-ray luminosity correlation. At the same time, it has to be taken into account when deriving covering factors of obscuring material from MIR to bolometric luminosity ratios. Finally, we find a new tentative trend of increasing MIR emission size with increasing Eddington ratio.

scholarly journals The IR Emission Features and Hydrogenated Amorphous Carbon (HAC) Particles

1989 ◽  
Vol 135 ◽  
pp. 141-146
Author(s):  
W. W. Duley
Keyword(s):  
Amorphous Carbon ◽  
Interstellar Dust ◽  
Near Infrared ◽  
High Energy ◽  
Radiative Relaxation ◽  
Hydrogenated Amorphous Carbon ◽  
Nir Emission ◽  
Extended Red Emission ◽  
Ir Emission ◽  
Hydrogenated Amorphous

Various sources of non-equilibrium radiation from interstellar dust are discussed. It is shown that the existence of cirrus emission at 12 and 25 μm is consistent with the presence of amorphous carbon dust and arises from thermal spikes within ≃ 10å subvolumes of normal (0.01-0.1 μm radius) dust grains. The 3.28 μm unidentified infrared (UIR) feature also arises in this way, as the radiative relaxation of high energy vibrational modes accompanying a thermal spike in hydrogenated amorphous carbon. Extended red emission (ERE) and near-infrared (NIR) emission are also discussed and are postulated to originate as edge and defect luminescence from HAC solids with bandgaps Eg ≲ 2.5eV.

scholarly journals Infrared Emission from AGN

1999 ◽  
Vol 194 ◽  
pp. 25-38
Author(s):  
D. B. Sanders
Keyword(s):  
Near Infrared ◽  
High Redshift ◽  
Dust Emission ◽  
Far Infrared ◽  
Infrared Emission ◽  
Substantial Fraction ◽  
Bolometric Luminosity ◽  
Submillimeter Wavelengths ◽  
Infrared Background ◽  
X Ray Background

Infrared observations of complete samples of active galactic nuclei (AGN) have shown that a substantial fraction of their bolometric luminosity is emitted at wavelengths ˜8–1000μm. In radio-loud and Blazar-like objects much of this emission appears to be direct non-thermal synchrotron radiation. However, in the much larger numbers of radio-quiet AGN it is now clear that thermal dust emission is responsible for the bulk of radiation from the near-infrared through submillimeter wavelengths. Luminous infrared-selected AGN are often surrounded by powerful nuclear starbursts, both of which appear to be fueled by enormous supplies of molecular gas and dust funneled into the nuclear region during the strong interaction/merger of gas rich disks. All-sky surveys in the infrared show that luminous infrared AGN are at least as numerous as optically-selected AGN of comparable bolometric luminosity, suggesting that AGN may spend a substantial fraction of their lifetime in a dust-enshrouded phase. The space density of luminous infrared AGN at high redshift may be sufficient to account for much of the X-Ray background, and for a substantial fraction of the far-infrared background as well. These objects plausibly represent a major epoch in the formation of spheroids and massive black holes (MBH).

NITROGEN INCORPORATED HYDROGENATED AMORPHOUS CARBON THIN FILMS DEPOSITED BY MICROWAVE SURFACE-WAVE PLASMA CHEMICAL VAPOR DEPOSITION

2009 ◽  
Vol 23 (09) ◽  
pp. 2159-2165 ◽  
Author(s):  
SUDIP ADHIKARI ◽  
MASAYOSHI UMENO
Keyword(s):  
Thin Films ◽  
Chemical Vapor Deposition ◽  
Surface Wave ◽  
Amorphous Carbon ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Plasma Chemical ◽  
Hydrogenated Amorphous Carbon ◽  
Plasma Chemical Vapor Deposition ◽  
Hydrogenated Amorphous

Nitrogen incorporated hydrogenated amorphous carbon (a-C:N:H) thin films have been deposited by microwave surface-wave plasma chemical vapor deposition on silicon and quartz substrates, using helium, methane and nitrogen ( N 2) as plasma source. The deposited a-C:N:H films were characterized by their optical, structural and electrical properties through UV/VIS/NIR spectroscopy, Raman spectroscopy, atomic force microscope and current-voltage characteristics. The optical band gap decreased gently from 3.0 eV to 2.5 eV with increasing N 2 concentration in the films. The a-C:N:H film shows significantly higher electrical conductivity compared to that of N 2-free a-C:H film.

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