We present high angular resolution (∼80 mas) ALMA continuum images of the SN 1987A system, together with CO J = 2 1, J = 6 5, and SiO J = 5 4 to J = 7 6 images, which clearly resolve the ejecta (dust ...continuum and molecules) and ring (synchrotron continuum) components. Dust in the ejecta is asymmetric and clumpy, and overall the dust fills the spatial void seen in H images, filling that region with material from heavier elements. The dust clumps generally fill the space where CO J = 6 5 is fainter, tentatively indicating that these dust clumps and CO are locationally and chemically linked. In these regions, carbonaceous dust grains might have formed after dissociation of CO. The dust grains would have cooled by radiation, and subsequent collisions of grains with gas would also cool the gas, suppressing the CO J = 6 5 intensity. The data show a dust peak spatially coincident with the molecular hole seen in previous ALMA CO J = 2 1 and SiO J = 5 4 images. That dust peak, combined with CO and SiO line spectra, suggests that the dust and gas could be at higher temperatures than the surrounding material, though higher density cannot be totally excluded. One of the possibilities is that a compact source provides additional heat at that location. Fits to the far-infrared-millimeter spectral energy distribution give ejecta dust temperatures of 18-23 K. We revise the ejecta dust mass to Mdust = 0.2-0.4 for carbon or silicate grains, or a maximum of <0.7 for a mixture of grain species, using the predicted nucleosynthesis yields as an upper limit.
Abstract
JWST Near Infrared Camera (NIRCam) observations at 1.5–4.5
μ
m have provided broadband and narrowband imaging of the evolving remnant of SN 1987A with unparalleled sensitivity and spatial ...resolution. Comparing with previous marginally spatially resolved Spitzer Infrared Array Camera (IRAC) observations from 2004 to 2019 confirms that the emission arises from the circumstellar equatorial ring (ER), and the current brightness at 3.6 and 4.5
μ
m was accurately predicted by extrapolation of the declining brightness tracked by IRAC. Despite the regular light curve, the NIRCam observations clearly reveal that much of this emission is from a newly developing outer portion of the ER. Spots in the outer ER tend to lie at position angles in between the well-known ER hotspots. We show that the bulk of the emission in the field can be represented by five standard spectral energy distributions, each with a distinct origin and spatial distribution. This spectral decomposition provides a powerful technique for distinguishing overlapping emission from the circumstellar medium and the supernova ejecta, excited by the forward and reverse shocks, respectively.
The equatorial ring of Supernova (SN) 1987A has been exposed to forward shocks from the SN blast wave, and it has been suggested that these forward shocks have been causing ongoing destruction of ...dust in the ring. We obtained Stratospheric Observatory For Infrared Astronomy The Faint Object InfraRed CAmera for the SOFIA Telescope (FORCAST) 11.1, 19.7, and 31.5 |$\mu \rm m$| photometry of SN 1987A in 2016. Compared with Spitzer measurements 10 yr earlier, the 31.5 |$\mu \rm m$| flux has significantly increased. The excess at 31.5 |$\mu \rm m$| appears to be related to the Herschel 70 |$\mu \rm m$| excess, which was detected 5 yr earlier. The dust mass needed to account for the 31.5–70 |$\mu \rm m$| excess is 3–7 × 10^−4 M_⊙, more than 10 times larger than the ring dust mass (∼1 × 10^−5 M_⊙) estimate from the data 10 yr earlier. We argue that dust grains are re-formed or grown in the post-shock regions in the ring after forward shocks have destroyed pre-existing dust grains in the ring and released refractory elements into gas. In the post-shock region, atoms can stick to surviving dust grains, and the dust mass may have increased (grain growth), or dust grains might have condensed directly from the gas. An alternative possibility is that the outer part of the expanding ejecta dust might have been heated by X-ray emission from the circumstellar ring. The future development of this excess could reveal whether grains are reformed in the post-shocked region of the ring or eject dust is heated by X-ray.
ABSTRACT
We present polarization observations of the young supernova remnant (SNR) Cas A using the High-resolution Airborne Wideband Camera-Plus (HAWC +) instrument onboard the Stratospheric ...Observatory for Infrared Astronomy (SOFIA). The polarization map at 154 $\mu$m reveals dust grains with strong polarization fractions (5–30 per cent), supporting previous measurements made over a smaller region of the remnant at 850 $\mu$m. The 154-$\mu$m emission and the polarization signal is coincident with a region of cold dust observed in the southeastern shell and in the unshocked central ejecta. The highly polarized far-IR emission implies the grains are large (>0.14 $\mu$m) and silicate-dominated. The polarization level varies across the SNR, with an inverse correlation between the polarization degree and the intensity and smaller polarization angle dispersion for brighter SNR emission. Stronger polarization is detected between the bright structures. This may result from a higher collision rate between the gas and dust producing a lower grain alignment efficiency where the gas density is higher. We use the dust emission to provide an estimate of the magnetic field strength in Cas A using the Davis–Chandrasekhar–Fermi method. The high polarization level is direct evidence that grains are highly elongated and strongly aligned with the magnetic field of the SNR. The dust mass from the polarized region is 0.14 ± 0.04 M⊙, a lower limit of the amount of dust present within the ejecta of Cas A. This result strengthens the hypothesis that core-collapse SNe are an important contributor to the dust mass in high redshift galaxies.
Abstract
We present here far-infrared photometry of galaxies in a sample that is relatively unexplored at these wavelengths: low-metallicity dwarf galaxies with moderate star formation rates. Four ...dwarf irregular galaxies from the
Little Things
survey are considered, with deep Herschel PACS and SPIRE observations at 100, 160, 250, 350, and 500
μ
m. Results from modified blackbody fits indicate that these galaxies have low dust masses and cooler dust temperatures than more actively star-forming dwarfs, occupying the lowest
L
TIR
and
M
dust
regimes seen among these samples. Dust-to-gas mass ratios of ∼10
−5
are lower, overall, than in more massive and active galaxies but are roughly consistent with the broken power-law relation between the dust-to-gas ratio and metallicity found for other low-metallicity systems. Chemical evolution modeling suggests that these dwarf galaxies are likely forming very little dust via stars or grain growth and have very high dust destruction rates.
The amount of dust estimated from infrared to sub-millimetre (submm) observations strongly depends on assumptions of different grain sizes, compositions and optical properties. Here we use a simple ...model of thermal emission from cold silicate/carbon dust at a range of dust grain temperatures and fit the spectral energy distribution (SED) of the Crab nebula as a test. This can lower the derived dust mass for the Crab by ∼50 per cent and 30–40 per cent for astronomical silicates and amorphous carbon grains compared to recently published values (0.25 M⊙ → 0.12 M⊙ and 0.12 M⊙ → 0.072 M⊙, respectively), but the implied dust mass can also increase by as much as almost a factor of 6 (0.25 M⊙ → 1.14 M⊙ and 0.12 M⊙ → 0.71 M⊙) depending on assumptions regarding the sizes/temperatures of the coldest grains. The latter values are clearly unrealistic due to the expected metal budget, though. Furthermore, we show by a simple numerical experiment that if a cold-dust component does have a grain-temperature distribution, it is almost unavoidable that a two-temperature fit will yield an incorrect dust mass estimate. But we conclude that grain temperatures is not a greater uncertainty than the often poorly constrained emissivities (i.e. material properties) of cosmic dust, although there is clearly a need for improved dust emission models. The greatest complication associated with deriving dust masses still arises in the uncertainty in the dust composition.
ABSTRACT
We investigate the evolution in galactic dust mass over cosmic time through (i) empirically derived dust masses using stacked submillimetre fluxes at 850 μm in the COSMOS field and (ii) dust ...masses derived using a robust post-processing method on the results from the cosmological hydrodynamical simulation IllustrisTNG. We effectively perform a ‘self-calibration’ of the dust mass absorption coefficient by forcing the model and observations to agree at low redshift and then compare the evolution shown by the observations with that predicted by the model. We create dust mass functions (DMFs) based on the IllustrisTNG simulations from 0 < z < 0.5 and compare these with previously observed DMFs. We find a lack of evolution in the DMFs derived from the simulations, in conflict with the rapid evolution seen in empirically derived estimates of the low-redshift DMF. Furthermore, we observe a strong evolution in the observed mean ratio of dust mass to stellar mass of galaxies over the redshift range 0 < z < 5, whereas the corresponding dust masses from IllustrisTNG show relatively little evolution, even after splitting the sample into satellites and centrals. The large discrepancy between the strong observed evolution and the weak evolution predicted by IllustrisTNG plus post-processing may be explained by either strong cosmic evolution in the properties of the dust grains or limitations in the model. In the latter case, the limitation may be connected to previous claims that the neutral gas content of galaxies does not evolve fast enough in IllustrisTNG.
Mid-Infrared Imaging of Supernova 1987A Matsuura, Mikako; Wesson, Roger; Arendt, Richard G ...
Monthly notices of the Royal Astronomical Society,
11/2022, Volume:
517, Issue:
3
Journal Article
Peer reviewed
Open access
At a distance of 50 kpc, Supernova 1987A is an ideal target to study how a young supernova (SN) evolves in time. Its equatorial ring, filled with material expelled from the progenitor star about 20 ...000 yr ago, has been engulfed with SN blast waves. Shocks heat dust grains in the ring, emitting their energy at mid-infrared (IR) wavelengths We present ground-based 10–18 μm monitoring of the ring of SN 1987A from day 6067 to 12814 at a resolution of 0.5 arcsec, together with SOFIA photometry at 10–30 μm. The IR images in the 2000’s (day 6067–7242) showed that the shocks first began brightening the east side of the ring. Later, our mid-IR images from 2017 to 2022 (day 10952–12714) show that dust emission is now fading in the east, while it has brightened on the west side of the ring. Because dust grains are heated in the shocked plasma, which can emit X-rays, the IR and X-ray brightness ratio represent shock diagnostics. Until 2007 the IR to X-ray brightness ratio remained constant over time, and during this time shocks seemed to be largely influencing the east side of the ring. However, since then, the IR to X-ray ratio has been declining, due to increased X-ray brightness. Whether the declining IR brightness is because of dust grains being destroyed or being cooled in the post-shock regions will require more detailed modelling.
Far-reaching dust distribution in galaxy discs Smith, Matthew W. L.; Eales, Stephen A.; De Looze, Ilse ...
Monthly Notices of the Royal Astronomical Society,
10/2016, Volume:
462, Issue:
1
Journal Article
Peer reviewed
Open access
In most studies of dust in galaxies, dust is only detected from its emission to approximately the optical radius of the galaxy. By combining the signal of 110 spiral galaxies observed as part of the ...Herschel Reference Survey, we are able to improve our sensitivity by an order of magnitude over that for a single object. Here we report the direct detection of dust from its emission that extends out to at least twice the optical radius. We find that the distribution of dust is consistent with an exponential at all radii with a gradient of ∼−1.7 dex
$R_{25}^{-1}$
. Our dust temperature declines linearly from ∼25 K in the centre to 15 K at R
25 from where it remains constant out to ∼2.0 R
25. The surface density of dust declines with radius at a similar rate to the surface density of stars but more slowly than the surface density of the star-formation rate. Studies based on dust extinction and reddening of high-redshift quasars have concluded that there are substantial amounts of dust in intergalactic space. By combining our results with the number counts and angular correlation function from the SDSS, we show that with Milky Way-type dust we can explain the reddening of the quasars by the dust within galactic discs alone. Given the uncertainties in the properties of any intergalactic dust, we cannot rule out its existence, but our results show that statistical investigations of the dust in galactic haloes that use the reddening of high-redshift objects must take account of the dust in galactic discs.
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