scholarly journals Dust evolution across the Horsehead nebula

2020 ◽  
Vol 639 ◽  
pp. A144
Author(s):  
T. Schirmer ◽  
A. Abergel ◽  
L. Verstraete ◽  
N. Ysard ◽  
M. Juvela ◽  
...  
Keyword(s):  
Interstellar Dust ◽  
Dust Emission ◽  
Outer Part ◽  
Minimum Size ◽  
Gas Temperature ◽  
Physical Conditions ◽  
Power Law Exponent ◽  
Dust Composition ◽  
Dust Evolution ◽  
Diffuse Medium

Context. Micro-physical processes on interstellar dust surfaces are tightly connected to dust properties (i.e. dust composition, size, and shape) and play a key role in numerous phenomena in the interstellar medium (ISM). The large disparity in physical conditions (i.e. density and gas temperature) in the ISM triggers an evolution of dust properties. The analysis of how dust evolves with the physical conditions is a stepping stone towards a more thorough understanding of interstellar dust. Aims. We highlight dust evolution in the Horsehead nebula photon-dominated region. Methods. We used Spitzer/IRAC (3.6, 4.5, 5.8 and 8 μm) and Spitzer/MIPS (24 μm) together with Herschel/PACS (70 and 160 μm) and Herschel/SPIRE (250, 350 and 500 μm) to map the spatial distribution of dust in the Horsehead nebula over the entire emission spectral range. We modelled dust emission and scattering using the THEMIS interstellar dust model together with the 3D radiative transfer code SOC. Results. We find that the nano-grain dust-to-gas ratio in the irradiated outer part of the Horsehead is 6–10 times lower than in the diffuse ISM. The minimum size of these grains is 2–2.25 times larger than in the diffuse ISM, and the power-law exponent of their size distribution is 1.1–1.4 times lower than in the diffuse ISM. In the denser part of the Horsehead nebula, it is necessary to use evolved grains (i.e. aggregates, with or without an ice mantle). Conclusions. It is not possible to explain the observations using grains from the diffuse medium. We therefore propose the following scenario to explain our results. In the outer part of the Horsehead nebula, all the nano-grain have not yet had time to re-form completely through photo-fragmentation of aggregates and the smallest of the nano-grain that are sensitive to the radiation field are photo-destroyed. In the inner part of the Horsehead nebula, grains most likely consist of multi-compositional mantled aggregates.

scholarly journals Resolved spectral variations of the centimetre-wavelength continuum from the ρ Oph W photo-dissociation-region

2021 ◽  
Author(s):  
Simon Casassus ◽  
Matías Vidal ◽  
Carla Arce-Tord ◽  
Clive Dickinson ◽  
Glenn J White ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Dust Emission ◽  
Image Synthesis ◽  
Microwave Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Parametric Image ◽  
Physical Conditions ◽  
Morphological Differences ◽  
Dust Grain

Abstract Cm-wavelength radio continuum emission in excess of free-free, synchrotron and Rayleigh-Jeans dust emission (excess microwave emission, EME), and often called ‘anomalous microwave emission’, is bright in molecular cloud regions exposed to UV radiation, i.e. in photo-dissociation regions (PDRs). The EME correlates with IR dust emission on degree angular scales. Resolved observations of well-studied PDRs are needed to compare the spectral variations of the cm-continuum with tracers of physical conditions and of the dust grain population. The EME is particularly bright in the regions of the ρ Ophiuchi molecular cloud (ρ Oph) that surround the earliest type star in the complex, HD 147889, where the peak signal stems from the filament known as the ρ Oph-W PDR. Here we report on ATCA observations of ρ Oph-W that resolve the width of the filament. We recover extended emission using a variant of non-parametric image synthesis performed in the sky plane. The multi-frequency 17 GHz to 39 GHz mosaics reveal spectral variations in the cm-wavelength continuum. At ∼30 arcsec resolutions, the 17-20 GHz intensities follow tightly the mid-IR, Icm∝I(8 μm), despite the breakdown of this correlation on larger scales. However, while the 33-39 GHz filament is parallel to IRAC 8 μm, it is offset by 15–20 arcsec towards the UV source. Such morphological differences in frequency reflect spectral variations, which we quantify spectroscopically as a sharp and steepening high-frequency cutoff, interpreted in terms of the spinning dust emission mechanism as a minimum grain size acutoff ∼ 6 ± 1 Å that increases deeper into the PDR.

scholarly journals Spitzer IRS Observations of Low-Mass Seyfert Galaxies

2009 ◽  
Vol 5 (S267) ◽  
pp. 268-268
Author(s):  
Carol E. Thornton ◽  
Aaron J. Barth ◽  
Luis C. Ho ◽  
Jenny E. Greene
Keyword(s):  
Dust Emission ◽  
Seyfert Galaxies ◽  
Sloan Digital Sky Survey ◽  
Physical Conditions ◽  
Sky Survey ◽  
Low Mass ◽  
Ngc 4395 ◽  
Black Hole Masses

The Sloan Digital Sky Survey has made it possible to identify the first samples of active galaxies with estimated black hole masses below ~ 106M⊙. We have obtained Spitzer IRS low-resolution spectra, covering 5–38 μm, of a sample of 41 Seyfert galaxies with low-mass black holes. Our sample includes SDSS-selected objects from the low-mass Seyfert 1 sample of Greene & Ho (2004) and the low-mass Seyfert 2 sample of Barth et al. (2008), as well as NGC 4395 and POX 52. The goals of this work are to examine the dust emission properties of these objects and investigate the relationship between type 1 and type 2 AGNs at low luminosities and low masses, to search for evidence of star formation, and to use emission-line diagnostics to constrain physical conditions within the narrow-line regions. Here we present preliminary results from this project.

scholarly journals SEDIGISM: the kinematics of ATLASGAL filaments

2018 ◽  
Vol 619 ◽  
pp. A166 ◽  
Author(s):  
M. Mattern ◽  
J. Kauffmann ◽  
T. Csengeri ◽  
J. S. Urquhart ◽  
S. Leurini ◽  
...  
Keyword(s):  
Unit Length ◽  
Dust Emission ◽  
Free Fall ◽  
Outer Radius ◽  
Line Of Sight ◽  
Fall Velocity ◽  
Automated Algorithm ◽  
Power Law Exponent ◽  
Continuum Data ◽  
Self Gravity

Analyzing the kinematics of filamentary molecular clouds is a crucial step toward understanding their role in the star formation process. Therefore, we study the kinematics of 283 filament candidates in the inner Galaxy, that were previously identified in the ATLASGAL dust continuum data. The 13CO(2 – 1) and C18O(2 – 1) data of the SEDIGISM survey (Structure, Excitation, and Dynamics of the Inner Galactic Inter Stellar Medium) allows us to analyze the kinematics of these targets and to determine their physical properties at a resolution of 30′′ and 0.25 km s−1. To do so, we developed an automated algorithm to identify all velocity components along the line-of-sight correlated with the ATLASGAL dust emission, and derive size, mass, and kinematic properties for all velocity components. We find two-third of the filament candidates are coherent structures in position-position-velocity space. The remaining candidates appear to be the result of a superposition of two or three filamentary structures along the line-of-sight. At the resolution of the data, on average the filaments are in agreement with Plummer-like radial density profiles with a power-law exponent of p ≈ 1.5 ± 0.5, indicating that they are typically embedded in a molecular cloud and do not have a well-defined outer radius. Also, we find a correlation between the observed mass per unit length and the velocity dispersion of the filament of m ∝ σv2. We show that this relation can be explained by a virial balance between self-gravity and pressure. Another possible explanation could be radial collapse of the filament, where we can exclude infall motions close to the free-fall velocity.

scholarly journals New Millimetre Measurements and the Radio to X-ray Continua of Active Galactic Nuclei

1989 ◽  
Vol 134 ◽  
pp. 393-395
Author(s):  
A. Lawrence
Keyword(s):  
Energy Distribution ◽  
Power Law ◽  
Interstellar Dust ◽  
Dust Emission ◽  
Good Argument ◽  
X Ray ◽  
Near Ir ◽  
Superluminal Motion ◽  
Order Of Magnitude ◽  
Phd Thesis

I am one of a large team studying an X-ray flux limited sample of 35 AGN, at radio (Unger et al 1987 MNRAS 228 521), IR (Ward et al 1987 ApJ 315 74 and Carleton et al 1987 ApJ 318 595), optical-UV (Boisson et al in preparation), and X-ray (Turner PhD thesis, Leicester) wavelengths. A gap in the data which we have just started to fill is the millimetre region. (Lawrence, Ward, Elvis, Robson, Smith, Duncan, and Rowan-Robinson). In Jan/Feb 1988 we made measurements of twelve objects at 800 and 1100 micron, using the ROE/QMC bolometer, UKT14, on the new UK/Dutch/Canadian facility on Mauna Kea, the James Clerk Maxwell Telescope, reaching 1 sigma sensitivity of ∼15–20 mJy, an order of magnitude improvement over previous data. The four radio loud objects measured were easily detected, as expected. These all have a strong blazar component, showing smooth but curved spectra over many decades, possibly log-Gaussian in form (Landau et al 1986 ApJ 308 78), or alternatively explicable by a small number of power-law components (Robson et al 1988 MNRAS in press). In any case, other evidence points to non-thermal radiation by a relativistically moving feature (high polarization, strong variability, superluminal motion). Eight radio quiet objects were measured, and upper limits only found, except for a possible four sigma detection of N2992. In all cases, the mm limits are far below the 100 micron IRAS fluxes. In four of the nearest objects, this is not too surprising, as fluxes are rising steeply throughout 12 to 100 micron, a sign that the IRAS data is dominated by cool interstellar dust emission (“cirrus”) from the discs of the parent galaxies. However we can also say that any postulated power law component of spectral index ∼1 dominating the near-IR, must become self-absorbed around ∼200 micron if the mm limits are not to be exceeded. Four rather more interesting objects are shown in Fig. 1. Again, any underlying power-law component must be self-absorbed by ∼100 micron, but is not clear that such a power-law is needed. N5506 and IC4329A have falling optical energy distributions, and large H α/Hβ ratios; on the other hand, the IR continuum lies well above the X-ray level, so there is good argument for absorption and re-radiation by dust. N4151, while flat through the near-IR-optical, has a large hump centred at ∼25 micron. Particularly important here are further new measurements by Engargiola et al (1987, ApJ in press),and Edelson et al (1988, preprint) which show the energy distribution to be falling so steeply from 155 to 438 micron that self-absorbed synchrotron is ruled out in this region. In fact, the whole energy distribution from mm to UV can be modelled without a power law at all, as shown in Fig 2. This uses a starburst component (from Rowan-Robinson and Crawford 1988, MNRAS in press), hot dust represented by three greybodies at 200K, 500K, and 1000K, starlight from a nuclear cusp, and a blackbody at 30,000K. Even MKN590, which at first sight looks like a power-law, can be modelled by similar components (Fig. 3).

scholarly journals The Interstellar Dust Emission Seen by ISO

1998 ◽  
Vol 11 (2) ◽  
pp. 1142-1144 ◽  
Author(s):  
J.L. Puget
Keyword(s):  
Interstellar Medium ◽  
Small Molecules ◽  
Interstellar Dust ◽  
Solid Phase ◽  
Dust Emission ◽  
Atom Clusters ◽  
Interstellar Grains ◽  
Small Atom

Among the important contributions of ISO to the physics of the interstellar medium, this paper concentrates only on the emission from the solid phase (the interstellar grains) and the small atom clusters which are the bridge between the grains and the small molecules with less than about 10 atoms.

scholarly journals Three-dimensional maps of interstellar dust in the Local Arm: using Gaia, 2MASS, and APOGEE-DR14

2018 ◽  
Vol 616 ◽  
pp. A132 ◽  
Author(s):  
R. Lallement ◽  
L. Capitanio ◽  
L. Ruiz-Dern ◽  
C. Danielski ◽  
C. Babusiaux ◽  
...  
Keyword(s):  
Interstellar Dust ◽  
Large Scale ◽  
Galactic Plane ◽  
Large Fraction ◽  
Complex Structure ◽  
Dust Emission ◽  
Three Dimensional ◽  
Red Giants ◽  
Photometric Calibration ◽  
The One

Context. Gaia data and stellar surveys open the way to the construction of detailed 3D maps of the Galactic interstellar (IS) dust based on the synthesis of star distances and extinctions. Dust maps are tools of broad use, also for Gaia-related Milky Way studies. Aims. Reliable extinction measurements require very accurate photometric calibrations. We show the first step of an iterative process linking 3D dust maps and photometric calibrations, and improving them simultaneously. Methods. Our previous 3D map of nearby IS dust was used to select low-reddening SDSS/APOGEE-DR14 red giants, and this database served for an empirical effective temperature- and metallicity-dependent photometric calibration in the Gaia G and 2MASS Ks bands. This calibration has been combined with Gaia G-band empirical extinction coefficients recently published, G, J, and Ks photometry and APOGEE atmospheric parameters to derive the extinction of a large fraction of the survey targets. Distances were estimated independently using isochrones and the magnitude-independent extinction KJ−Ks. This new dataset has been merged with the one used for the earlier version of dust map. A new Bayesian inversion of distance-extinction pairs has been performed to produce an updated 3D map. Results. We present several properties of the new map. A comparison with 2D dust emission reveals that all large dust shells seen in emission at middle and high latitudes are closer than 300 pc. The updated distribution constrains the well-debated, X-ray bright North Polar Spur to originate beyond 800 pc. We use the Orion region to illustrate additional details and distant clouds. On the large scale the map reveals a complex structure of the Local Arm. Chains of clouds of 2–3 kpc in length appear in planes tilted by ≃15° with respect to the Galactic plane. A series of cavities oriented along a l ≃ 60–240° axis crosses the Arm. Conclusions. The results illustrate the ongoing synergy between 3D mapping of IS dust and stellar calibrations in the context of Gaia. Dust maps provide prior foregrounds for future calibrations appropriate to different target characteristics or ranges of extinction, allowing us in turn to increase extinction data and produce more detailed and extended maps.

scholarly journals Dust evolution in pre-stellar cores

2020 ◽  
Vol 228 ◽  
pp. 00013
Author(s):  
Charlène Lefèvre ◽  
Laurent Pagani ◽  
Bilal Ladjelate ◽  
Michiel Min ◽  
Hiroyuki Hirashita ◽  
...  
Keyword(s):  
Life Cycle ◽  
Open Access ◽  
Interstellar Medium ◽  
Building Blocks ◽  
Dust Grains ◽  
Multi Wavelength ◽  
Dust Evolution ◽  
Diffuse Medium

Dust grains are the building blocks of future planets. They evolve in size, shape and composition during the life cycle of the interstellar medium. We seek to understand the process which leads from diffuse medium grains to dust grains in the vicinity of protostars inside disks. As a first step, we propose to characterize the dust evolution inside pre-stellar cores thanks to multi-wavelength observations. We will present how NIKA2 maps are crucial to better constrain dust properties and we will introduce SIGMA: a new flexible dust model in open access.

scholarly journals Determining the fraction of dust heating from young and old stellar populations with 3D dust radiative transfer

2015 ◽  
Vol 11 (A29B) ◽  
pp. 178-179
Author(s):  
Giovanni Natale ◽  
Cristina C. Popescu ◽  
Richard. J. Tuffs ◽  
Victor P. Debattista ◽  
Jörg Fischera ◽  
...  
Keyword(s):  
Star Formation ◽  
Radiative Transfer ◽  
Interstellar Dust ◽  
Star Formation Rate ◽  
Local Heating ◽  
Formation Rate ◽  
Dust Emission ◽  
Stellar Populations ◽  
Galaxy Model ◽  
Different Response

AbstractA major difficulty hampering the accuracy of UV/optical star formation rate tracers is the effect of interstellar dust, absorbing and scattering light produced by both young and old stellar populations (SPs). Although empirically calibrated corrections or energy balance SED fitting are often used for fast de-reddening of galaxy stellar emission, eventually only radiative transfer calculations can provide self-consistent predictions of galaxy model spectra, taking into account important factors such as galaxy inclination, different morphological components, non-local heating of the dust and scattered radiation. In addition, dust radiative transfer can be used to determine the fraction of monochromatic dust emission powered by either young or old SPs. This calculation needs to take into account the different response of the dust grains to the UV and optical radiation field, depending on the grain size and composition. We determined the dust heating fractions, on both global and local scales, for a high-resolution galaxy model by using our 3D ray-tracing dust radiative transfer code “DART-Ray”. We show the results obtained using this method and discuss the consequences for star formation rate indicators.

scholarly journals 7.6. Dust composition, energetics, and morphology of the Galactic center

1998 ◽  
Vol 184 ◽  
pp. 303-304
Author(s):  
Kin-Wing Chan ◽  
S. H. Moseley ◽  
S. Casey ◽  
J. P. Harrington ◽  
E. Dwek ◽  
...  
Keyword(s):  
Galactic Center ◽  
Broad Band ◽  
Dust Emission ◽  
Emission Feature ◽  
Elemental Abundances ◽  
Evolved Stars ◽  
The Galaxy ◽  
Dust Composition ◽  
Circumnuclear Disk ◽  
Theoretical Results

Spectra at 16 - 45 μm of several regions within the central 80″ of the Galaxy have been obtained at 20″ resolution using the Goddard Cryogenic Grating Spectrometer No. 2 on the Kuiper Airborne Observatory. A broad band of excess emission extending from 24 to 45 μm is present in the spectra at positions covering the “tongue” and the inner edge of the circumnuclear disk. A similar dust emission feature has been observed in some carbon-rich evolved stars and in a nitrogen-rich evolved massive star. The observations reported here are the first detection of this dust emission feature in the interstellar medium. After considering several possible candidates of the carrier for this 30 μm dust feature, we find that MgS is the best owing to its good fit to the observed spectra. The origin of this ~ 30 μm feature in the Galactic center is unknown. Based on the theoretical results of dust condensation and elemental abundances in a supernova, we find that the supernovae in the central 500 pc could provide the amount of MgS dust, which we proposed as the carrier of the 30 μm dust feature, observed in the central 3 pc.

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