91 research outputs found
DustKING, the story continues : dust attenuation in NGC 628
Dust attenuation is a crucial but highly uncertain parameter that hampers the determination of in- trinsic galaxy properties, such as stellar masses, star formation rates and star formation histories. The shape of the dust attenuation law is not expected to be uniform between galaxies, nor within a galaxy. Our DustKING project was introduced at the first BINA workshop in 2016 and aims to study the variations of dust attenuation curves in nearby galaxies. At the second BINA workshop in 2018, I presented the results of our pilot study for the spiral galaxy NGC 628. We find that the average attenuation law of this galaxy is characterised by a MW-like bump and a steep UV slope. Furthermore, we observe intriguing variations within the galaxy, with regions of high AV exhibiting a shallower attenuation curve. Finally, we discuss how our work might benefit from data taken with the UVIT from the Indian AstroSat mission
The recent star formation history of NGC 628 on resolved scales
Star formation histories (SFHs) are integral to our understanding of galaxy evolution. We can study recent SFHs by comparing the star formation rate (SFR) calculated using different tracers, as each probes a different timescale. We aim to calibrate a proxy for the present-day rate of change in SFR, dSFR/dt, which does not require full spectral energy distribution (SED) modeling and depends on as few observables as possible, to guarantee its broad applicability. To achieve this, we create a set of models in CIGALE and define a SFR change diagnostic as the ratio of the SFR averaged over the past 5 and 200 Myr, ⟨SFR5⟩/⟨SFR200⟩, probed by the Hα −FUV colour. We apply ⟨SFR5⟩/⟨SFR200⟩ to the nearby spiral NGC 628 and find that its star formation activity has overall been declining in the recent past, with the spiral arms, however, maintaining a higher level of activity. The impact of the spiral arm structure is observed to be stronger on ⟨SFR5⟩/⟨SFR200⟩ than on the star formation efficiency (SFEH2). In addition, increasing disk pressure tends to increase recent star formation, and consequently ⟨SFR5⟩/⟨SFR200⟩. We conclude that ⟨SFR5⟩/⟨SFR200⟩ is sensitive to the molecular gas content, spiral arm structure, and disk pressure. The ⟨SFR5⟩/⟨SFR200⟩ indicator is general and can be used to reconstruct the recent SFH of any star-forming galaxy for which Hα, FUV, and either mid- or far-IR photometry is available, without the need of detailed modeling
The distribution of interstellar dust in CALIFA edge-on galaxies via oligochromatic radiative transfer fitting
We investigate the amount and spatial distribution of interstellar dust in
edge-on spiral galaxies, using detailed radiative transfer modeling of a
homogeneous sample of 12 galaxies selected from the CALIFA survey. Our
automated fitting routine, FitSKIRT, was first validated against artificial
data. This is done by simultaneously reproducing the SDSS -, -, - and
-band observations of a toy model in order to combine the information
present in the different bands. We show that this combined, oligochromatic
fitting, has clear advantages over standard monochromatic fitting especially
regarding constraints on the dust properties. We model all galaxies in our
sample using a three-component model, consisting of a double exponential disc
to describe the stellar and dust discs and using a S\'ersic profile to describe
the central bulge. The full model contains 19 free parameters, and we are able
to constrain all these parameters to a satisfactory level of accuracy without
human intervention or strong boundary conditions. Apart from two galaxies, the
entire sample can be accurately reproduced by our model. We find that the dust
disc is about 75% more extended but only half as high as the stellar disc. The
average face-on optical depth in the V-band is and the spread of
within our sample is quite substantial, which indicates that some spiral
galaxies are relatively opaque even when seen face-on.Comment: 18 pages, 6 figures, 4 tables, Accepted for publication in MNRA
The dust mass in Cassiopeia A from infrared and optical line flux differences
The large quantities of dust that have been found in a number of high
redshift galaxies have led to suggestions that core-collapse supernovae (CCSNe)
are the main sources of their dust and have motivated the measurement of the
dust masses formed by local CCSNe. For Cassiopeia~A, an oxygen-rich remnant of
a Type~IIb CCSN, a dust mass of 0.6-1.1~M has already been determined
by two different methods, namely (a) from its far-infrared spectral energy
distribution and (b) from analysis of the red-blue emission line asymmetries in
its integrated optical spectrum. We present a third, independent, method for
determining the mass of dust contained within Cas~A. This compares the relative
fluxes measured in similar apertures from [O~{\sc iii}] far-infrared and
visual-region emission lines, taking into account foreground dust extinction,
in order to determine internal dust optical depths, from which corresponding
dust masses can be obtained. Using this method we determine a dust mass within
Cas~A of at least 0.99~M.Comment: Accepted by MNRAS, 17 pages, 12 figures. Author accepted manuscript.
Accepted on 21/03/2021. Deposited on 22/03/202
Dust survival rates in clumps passing through the Cas A reverse shock -- II. The impact of magnetic fields
Dust grains form in the clumpy ejecta of core-collapse supernovae where they
are subject to the reverse shock, which is able to disrupt the clumps and
destroy the grains. Important dust destruction processes include thermal and
kinetic sputtering as well as fragmentation and grain vaporization. In the
present study, we focus on the effect of magnetic fields on the destruction
processes. We have performed magneto-hydrodynamical simulations using AstroBEAR
to model a shock wave interacting with an ejecta clump. The dust transport and
destruction fractions are computed using our post-processing code Paperboats in
which the acceleration of grains due to the magnetic field and a procedure that
allows partial grain vaporization have been newly implemented. For the
oxygen-rich supernova remnant Cassiopeia A we found a significantly lower dust
survival rate when magnetic fields are aligned perpendicular to the shock
direction compared to the non-magnetic case. For a parallel field alignment,
the destruction is also enhanced but at a lower level. The survival fractions
depend sensitively on the gas density contrast between the clump and the
ambient medium and on the grain sizes. For a low-density contrast of ,
e.g., nm silicate grains are completely destroyed while the survival
fraction of m grains is per cent. For a high-density contrast of
, per cent of the nm grains survive while the survival
fraction of m grains is per cent. Alternative clump sizes or dust
materials (carbon) have non-negligible effects on the survival rate but have a
lower impact compared to density contrast, magnetic field strength, and grain
size.Comment: Accepted by MNRAS. Author accepted manuscript. Accepted on
23/01/2023. 24 pages, 21 Figure
High-resolution radiative transfer modelling of M33
The authors thank the anonymous reviewer, whose comments
have certainly improved the manuscript. The authors also thank
Peter Camps for valuable technical advice, along with all of
the participants at the recent SKIRT meeting for comments and
discussions. I.D.L. gratefully acknowledges the supports of the
Research Foundation – Flanders (FWO). M.W.L.S acknowledges
funding from the UK Science and Technology Facilities Council
consolidated grant ST/K000926/1. M.R. acknowledges support by
the research projects AYA2014-53506-P and AYA2017-84897P
from the Spanish Ministerio de Econom´ıa y Competitividad. This
research made use of MONTAGE (http://montage.ipac.caltech.edu/),
which is funded by the National Science Foundation under Grant
Number ACI-1440620, and was previously funded by the National
Aeronautics and Space Administration’s Earth Science Technology
Office, Computation Technologies Project, under Cooperative
Agreement Number NCC5-626 between NASA and the California
Institute of Technology. This research has made use of Astropy, a community-developed core PYTHON package for Astronomy (http:
//www.astropy.org/; Astropy Collaboration et al. 2013, 2018). This
research has made use of NumPy (http://www.numpy.org/; van der
Walt, Colbert & Varoquaux 2011), SciPy (http://www.scipy.org/),
andMatPlotLib (http://matplotlib.org/; Hunter 2007). This research
made use of APLpy, an open-source plotting package for PYTHON
(https://aplpy.github.io/; Robitaille & Bressert 2012).In this work, we characterize the contributions from both ongoing star formation and the
ambient radiation field in Local Group galaxy M33, as well as estimate the scale of the local
dust-energy balance (i.e. the scale at which the dust is re-emitting starlight generated in that
same region) in this galaxy through high-resolution radiative transfer (RT) modelling, with
defined stellar and dust geometries. We have characterized the spectral energy distribution
(SED) of M33 from UV to sub-mm wavelengths, at a spatial scale of 100 pc. We constructed
input maps of the various stellar and dust geometries for use in the RTmodelling. By modifying
our dust mix (fewer very small carbon grains and a lower silicate-to-carbon ratio as compared
to the Milky Way), we can much better fit the sub-mm dust continuum. Using this new dust
composition, we find that we are able to well reproduce the observed SED of M33 using our
adopted model. In terms of stellar attenuation by dust, we find a reasonably strong, broad
UV bump, as well as significant systematic differences in the amount of dust attenuation
when compared to standard SED modelling.We also find discrepancies in the residuals of the
spiral arms versus the diffuse interstellar medium (ISM), indicating a difference in properties
between these two regimes. The dust emission is dominated by heating due to the young stellar
populations at all wavelengths (∼80 per cent at 10 μm to ∼50 per cent at 1 mm). We find that
the local dust-energy balance is restored at spatial scales greater than around 1.5 kpc.Funding from the UK Science and Technology Facilities Council consolidated grant ST/K000926/1. M.R. acknowledges support by the research projects AYA2014-53506-P and AYA2017-84897P from the Spanish Ministerio de Economía y Competitividad. This research made use of MONTAGE (http://montage.ipac.caltech.edu/), which is funded by the National Science Foundation under Grant Number ACI-1440620, and was previously funded by the National Aeronautics and Space Administration’s Earth Science Technology Office, Computation Technologies Project, under Cooperative Agreement Number NCC5-626 between NASA and the California Institute of Technolog
From total destruction to complete survival: dust processing at different evolutionary stages in the supernova remnant Cassiopeia A
The expanding ejecta of supernova remnants (SNRs) are believed to form dust in dense clumps of gas. Before the dust can be expelled into the interstellar medium and contribute to the interstellar dust budget, it has to survive the reverse shock that is generated through the interaction of the preceding supernova blast wave with the surrounding medium. The conditions under which the reverse shock hits the clumps change with remnant age and define the dust survival rate. To study the dust destruction in the SNR Cassiopeia A, we conduct magnetohydrodynamical simulations of the evolution of a supernova blast wave and of the reverse shock. In a second step, we use these evolving conditions to model clumps that are disrupted by the reverse shock at different remnant ages. Finally, we compute the amount of dust that is destroyed by the impact of the reverse shock. We find that most of the dust in the SNR is hit by the reverse shock within the first 350 yr after the SN explosion. While the dust destruction in the first 200 yr is almost complete, we expect greater dust survival rates at later times and almost total survival for clumps that are first impacted at ages beyond 1000 yr. Integrated over the entire evolution of the SNR, the dust mass shows the lowest survival fraction (17 per cent) for the smallest grains (1 nm) and the highest survival fraction (28 per cent) for the largest grains (1000 nm)
Herschel SPIRE-FTS Observations of Excited CO and [CI] in the Antennae (NGC 4038/39): Warm and Cold Molecular Gas
We present Herschel SPIRE-FTS observations of the Antennae (NGC 4038/39), a
well studied, nearby ( Mpc) ongoing merger between two gas rich spiral
galaxies. We detect 5 CO transitions ( to ), both [CI]
transitions and the [NII] transition across the entire system, which
we supplement with ground based observations of the CO , and
transitions, and Herschel PACS observations of [CII] and [OI].
Using the CO and [CI] transitions, we perform both a LTE analysis of [CI], and
a non-LTE radiative transfer analysis of CO and [CI] using the radiative
transfer code RADEX along with a Bayesian likelihood analysis. We find that
there are two components to the molecular gas: a cold ( K)
and a warm ( K) component. By comparing the warm gas mass
to previously observed values, we determine a CO abundance in the warm gas of
. If the CO abundance is the same in the warm and
cold gas phases, this abundance corresponds to a CO luminosity-to-mass
conversion factor of $\alpha_{CO} \sim 7 \ M_{\odot}{pc^{-2} \ (K \ km \
s^{-1})^{-1}}_263\mu m\sim 0.01 L_{\odot}/M_{\odot}G_0\sim 1000$. Finally, we find
that a combination of turbulent heating, due to the ongoing merger, and
supernova and stellar winds are sufficient to heat the molecular gas.Comment: 50 pages, 15 figures, 8 tables, Accepted for publication in The
Astrophysical Journa
The applicability of FIR fine-structure lines as Star Formation Rate tracers over wide ranges of metallicities and galaxy types
We analyze the applicability of far-infrared fine-structure lines [CII] 158
micron, [OI] 63 micron and [OIII] 88 micron to reliably trace the star
formation rate (SFR) in a sample of low-metallicity dwarf galaxies from the
Herschel Dwarf Galaxy Survey and compare with a broad sample of galaxies of
various types and metallicities in the literature. We study the trends and
scatter in the relation between the SFR (as traced by GALEX FUV and MIPS 24
micron) and far-infrared line emission, on spatially resolved and global galaxy
scales, in dwarf galaxies. We assemble far-infrared line measurements from the
literature and infer whether the far-infrared lines can probe the SFR (as
traced by the total-infrared luminosity) in a variety of galaxy populations. In
metal-poor dwarfs, the [OI] and [OIII] lines show the strongest correlation
with the SFR with an uncertainty on the SFR estimates better than a factor of
2, while the link between [CII] emission and the SFR is more dispersed
(uncertainty factor of 2.6). The increased scatter in the SFR-L([CII]) relation
towards low metal abundances, warm dust temperatures, large filling factors of
diffuse, highly ionized gas suggests that other cooling lines start to dominate
depending on the density and ionization state of the gas. For the literature
sample, we evaluate the correlations for a number of different galaxy
populations. The [CII] and [OI] lines are considered to be reliable SFR tracers
in starburst galaxies, recovering the star formation activity within an
uncertainty of factor 2. [Abridged]Comment: 35 pages, 13 figures, accepted for publication in A&A on May 7th 201
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