457 research outputs found
A decade of ejecta dust formation in the Type IIn SN 2005ip
In order to understand the contribution of core-collapse supernovae to the
dust budget of the early universe, it is important to understand not only the
mass of dust that can form in core-collapse supernovae but also the location
and rate of dust formation. SN 2005ip is of particular interest since dust has
been inferred to have formed in both the ejecta and the post-shock region
behind the radiative reverse shock. We have collated eight optical archival
spectra that span the lifetime of SN 2005ip and we additionally present a new
X-shooter optical-near-IR spectrum of SN 2005ip at 4075d post-discovery. Using
the Monte Carlo line transfer code DAMOCLES, we have modelled the blueshifted
broad and intermediate width H, H and He I lines from 48d to
4075d post-discovery using an ejecta dust model. We find that dust in the
ejecta can account for the asymmetries observed in the broad and intermediate
width H, H and He I line profiles at all epochs and that it is
not necessary to invoke post-shock dust formation to explain the blueshifting
observed in the intermediate width post-shock lines. Using a Bayesian approach,
we have determined the evolution of the ejecta dust mass in SN 2005ip over 10
years presuming an ejecta dust model, with an increasing dust mass from
~10 M at 48d to a current dust mass of 0.1 M.Comment: Accepted by MNRAS, 17 pages, 11 figures. Author accepted manuscript.
Accepted on 04/03/19. Deposited on 07/03/1
Constraining early-time dust formation in core-collapse supernovae
There is currently a severe discrepancy between theoretical models of dust
formation in core-collapse supernovae (CCSNe), which predict
M of ejecta dust forming within days, and observations at
these epochs, which infer much lower masses. We demonstrate that, in the
optically thin case, these low dust masses are robust despite significant
observational and model uncertainties. For a sample of 11 well-observed CCSNe,
no plausible model reaches carbon dust masses above M, or
silicate masses above M. Optically thick models can
accommodate larger dust masses, but the dust must be clumped and have a low
() covering fraction to avoid conflict with data at optical wavelengths.
These values are insufficient to reproduce the observed infrared fluxes, and
the required covering fraction varies not only between SNe but between epochs
for the same object. The difficulty in reconciling large dust masses with
early-time observations of CCSNe, combined with well-established detections of
comparably large dust masses in supernova remnants, suggests that a mechanism
for late-time dust formation is necessary.Comment: 14 pages, 13 figures. MNRAS accepted 10/07/2
The Herschel exploitation of local galaxy Andromeda (HELGA) V: Strengthening the case for substantial interstellar grain growth
In this paper we consider the implications of the distributions of dust and
metals in the disc of M31. We derive mean radial dust distributions using a
dust map created from Herschel images of M31 sampling the entire far-infrared
(FIR) peak. Modified blackbodies are fit to approximately 4000 pixels with a
varying, as well as a fixed, dust emissivity index (beta). An overall metal
distribution is also derived using data collected from the literature. We use a
simple analytical model of the evolution of the dust in a galaxy with dust
contributed by stellar sources and interstellar grain growth, and fit this
model to the radial dust-to-metals distribution across the galaxy. Our analysis
shows that the dust-to-gas gradient in M31 is steeper than the metallicity
gradient, suggesting interstellar dust growth is (or has been) important in
M31. We argue that M31 helps build a case for cosmic dust in galaxies being the
result of substantial interstellar grain growth, while the net dust production
from stars may be limited. We note, however, that the efficiency of dust
production in stars, e.g., in supernovae (SNe) ejecta and/or stellar
atmospheres, and grain destruction in the interstellar medium (ISM) may be
degenerate in our simple model. We can conclude that interstellar grain growth
by accretion is likely at least as important as stellar dust production
channels in building the cosmic dust component in M31.Comment: 12 pages, 7 figures. Published in MNRAS 444, 797. This version is
updated to match the published versio
H-ATLAS/GAMA and HeViCS – dusty early-type galaxies in different environments
The Herschel Space Observatory has had a tremendous impact on the study of extragalactic dust. Specifically, early-type galaxies (ETG) have been the focus of several studies. In this paper, we combine results from two Herschel studies – a Virgo cluster study Herschel Virgo Cluster Survey (HeViCS) and a broader, low-redshift Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS)/Galaxy and Mass Assembly (GAMA) study – and contrast the dust and associated properties for similar mass galaxies. This comparison is motivated by differences in results exhibited between multiple Herschel studies of ETG. A comparison between consistent modified blackbody derived dust mass is carried out, revealing strong differences between the two samples in both dust mass and dust-to-stellar mass ratio. In particular, the HeViCS sample lacks massive ETG with as high a specific dust content as found in H-ATLAS. This is most likely connected with the difference in environment for the two samples. We calculate nearest neighbour environment densities in a consistent way, showing that H-ATLAS ETG occupy sparser regions of the local Universe, whereas HeViCS ETG occupy dense regions. This is also true for ETG that are not Herschel-detected but are in the Virgo and GAMA parent samples. Spectral energy distributions are fit to the panchromatic data. From these, we find that in H-ATLAS the specific star formation rate anticorrelates with stellar mass and reaches values as high as in our Galaxy. On the other hand HeViCS ETG appear to have little star formation. Based on the trends found here, H-ATLAS ETG are thought to have more extended star formation histories and a younger stellar population than HeViCS ETG
The selective effect of environment on the atomic and molecular gas-to-dust ratio of nearby galaxies in the Herschel Reference Survey
We combine dust, atomic (HI) and molecular (H) hydrogen mass
measurements for 176 galaxies in the Herschel Reference Survey to investigate
the effect of environment on the gas-to-dust mass ()
ratio of nearby galaxies. We find that, at fixed stellar mass, the average
ratio varies by no more than a factor of 2
when moving from field to cluster galaxies, with Virgo galaxies being slightly
more dust rich (per unit of gas) than isolated systems. Remarkably, once the
molecular and atomic hydrogen phases are investigated separately, we find that
\hi-deficient galaxies have at the same time lower
ratio but higher ratio than \hi-normal systems. In
other words, they are poorer in atomic but richer in molecular hydrogen if
normalized to their dust content. By comparing our findings with the
predictions of theoretical models, we show that the opposite behavior observed
in the and ratios is
fully consistent with outside-in stripping of the interstellar medium (ISM),
and is simply a consequence of the different distribution of dust, \hi\ and
H across the disk. Our results demonstrate that the small environmental
variations in the total ratio, as well as in the
gas-phase metallicity, do not automatically imply that environmental mechanisms
are not able to affect the dust and metal content of the ISM in galaxies.Comment: 11 pages, 6 figures, 2 tables. Accepted for publication in MNRA
Evidence for late-time dust formation in the ejecta of supernova SN~1995N from emission-line asymmetries
We present a study of the dust associated with the core-collapse supernova
SN~1995N. Infrared emission detected 14--15 years after the explosion was
previously attributed to thermally echoing circumstellar material associated
with the SN progenitor. We argue that this late-time emission is unlikely to be
an echo, and is more plausibly explained by newly formed dust in the supernova
ejecta, indirectly heated by the interaction between the ejecta and the CSM.
Further evidence in support of this scenario comes from emission line profiles
in spectra obtained 22 years after the explosion; these are asymmetric, showing
greater attenuation on the red wing, consistent with absorption by dust within
the expanding ejecta. The spectral energy distribution and emission line
profiles at epochs later than 5000 days are both consistent with the
presence of about 0.4~M of amorphous carbon dust. The onset of dust
formation is apparent in archival optical spectra, taken between 700 and 1700
days after the assumed explosion date. As this is considerably later than most
other instances where the onset of dust formation has been detected, we argue
that the explosion date must be later than previously assumed.Comment: 14 pages, 16 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
The bolometric and UV attenuation in normal spiral galaxies of the Herschel Reference Survey
The dust in nearby galaxies absorbs a fraction of the
UV-optical-near-infrared radiation produced by stars. This energy is
consequently re-emitted in the infrared. We investigate the portion of the
stellar radiation absorbed by spiral galaxies from the HRS by modelling their
UV-to-submillimetre spectral energy distributions. Our models provide an
attenuated and intrinsic SED from which we find that on average 32 % of all
starlight is absorbed by dust. We define the UV heating fraction as the
percentage of dust luminosity that comes from absorbed UV photons and find that
this is 56 %, on average. This percentage varies with morphological type, with
later types having significantly higher UV heating fractions. We find a strong
correlation between the UV heating fraction and specific star formation rate
and provide a power-law fit. Our models allow us to revisit the IRX-AFUV
relations, and derive these quantities directly within a self-consistent
framework. We calibrate this relation for different bins of NUV-r colour and
provide simple relations to relate these parameters. We investigated the
robustness of our method and we conclude that the derived parameters are
reliable within the uncertainties which are inherent to the adopted SED model.
This calls for a deeper investigation on how well extinction and attenuation
can be determined through panchromatic SED modelling.Comment: 14 pages, 7 figures. Accepted for publication in Astronomy &
Astrophysic
Towards understanding the relation between the gas and the attenuation in galaxies at kpc scales
[abridged]
Aims. The aim of the present paper is to provide new and more detailed
relations at the kpc scale between the gas surface density and the face-on
optical depth directly calibrated on galaxies, in order to compute the
attenuation not only for semi-analytic models but also observationally as new
and upcoming radio observatories are able to trace gas ever farther in the
Universe.
Methods. We have selected a sample of 4 nearby resolved galaxies and a sample
of 27 unresolved galaxies from the Herschel Reference Survey and the Very
Nearby Galaxies Survey, for which we have a large set of multi-wavelength data
from the FUV to the FIR including metallicity gradients for resolved galaxies,
along with radio HI and CO observations. For each pixel in resolved galaxies
and for each galaxy in the unresolved sample, we compute the face-on optical
depth from the attenuation determined with the CIGALE SED fitting code and an
assumed geometry. We determine the gas surface density from HI and CO
observations with a metallicity-dependent XCO factor.
Results. We provide new, simple to use, relations to determine the face-on
optical depth from the gas surface density, taking the metallicity into
account, which proves to be crucial for a proper estimate. The method used to
determine the gas surface density or the face-on optical depth has little
impact on the relations except for galaxies that have an inclination over 50d.
Finally, we provide detailed instructions on how to compute the attenuation
practically from the gas surface density taking into account possible
information on the metallicity.
Conclusions. Examination of the influence of these new relations on simulated
FUV and IR luminosity functions shows a clear impact compared to older oft-used
relations, which in turn could affect the conclusions drawn from studies based
on large scale cosmological simulations.Comment: 24 pages, 21 figures, accepted for publication in A&
HERschel Observations of Edge-on Spirals (HEROES). I: Far-infrared morphology and dust mass determination
Context. Edge-on spiral galaxies with prominent dust lanes provide us with an
excellent opportunity to study the distribution and properties of the dust
within them. The HEROES project was set up to observe a sample of seven large
edge-on galaxies across various wavelengths for this investigation.
Aims. Within this first paper, we present the Herschel observations and
perform a qualitative and quantitative analysis on them, and we derive some
global properties of the far infrared and submillimetre emission.
Methods. We determine horizontal and vertical profiles from the Herschel
observations of the galaxies in the sample and describe the morphology.
Modified black-body fits to the global fluxes, measured using aperture
photometry, result in dust temperatures and dust masses. The latter values are
compared to those that are derived from radiative transfer models taken from
the literature.
Results. On the whole, our Herschel flux measurements agree well with
archival values. We find that the exponential horizontal dust distribution
model often used in the literature generally provides a good description of the
observed horizontal profiles. Three out of the seven galaxies show signatures
of extended vertical emission at 100 and 160 {\mu}m at the 5{\sigma} level, but
in two of these it is probably due to deviations from an exactly edge-on
orientation. Only for NGC 4013, a galaxy in which vertically extended dust has
already been detected in optical images, we can detect vertically extended
dust, and the derived scaleheight agrees with the value estimated through
radiative transfer modelling. Our analysis hints at a correlation between the
dust scaleheight and its degree of clumpiness, which we infer from the
difference between the dust masses as calculated from modelling of optical data
and from fitting the spectral energy distribution of Herschel datapoints.Comment: 21 pages, 12 figures. Accepted for publication in Astronomy &
Astrophysic
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