A&A 654, A128 (2021) We characterize the ionized gas outflows in 15 low-redshift star-forming
galaxies, a Valpara\'iso ALMA Line Emission Survey (VALES) subsample, using
MUSE integral field ...spectroscopy and GAMA photometric broadband data. We
measure the emission-line spectra by fitting a double-component profile, with
the second and broader component being related to the outflowing gas. This
interpretation is in agreement with the correlation between the observed
star-formation rate surface density ($\Sigma_{\mathrm{SFR}}$) and the
second-component velocity dispersion ($\sigma_{\mathrm{2nd}}$), expected when
tracing the feedback component. By modelling the broadband spectra with spectra
energy distribution (SED) fitting and obtaining the star-formation histories of
the sample, we observe a small decrease in SFR between 100 and 10 Myr in
galaxies when the outflow H$\alpha$ luminosity contribution is increased,
indicating that the feedback somewhat inhibits the star formation within these
timescales. The observed emission-line ratios are best reproduced by
photoionization models when compared to shock-ionization, indicating that
radiation from young stellar population is dominant, and seems to be a
consequence of a continuous star-formation activity instead of a bursty event.
The outflow properties such as mass outflow rate ($\sim 0.1\,$M$_\odot$
yr$^{-1}$), outflow kinetic power ($\sim 5.2 \times 10^{-4}\%
L_{\mathrm{bol}}$) and mass loading factor ($\sim 0.12$) point towards a
scenario where the measured feedback is not strong and has a low impact on the
evolution of galaxies in general.
We investigate the dust energy balance for the edge-on galaxy IC2531, one of the seven galaxies in the HEROES sample. We perform a state-of-the-art radiative transfer modelling based, for the first ...time, on a set of optical and near-infrared galaxy images. We show that by taking into account near-infrared imaging in the modelling significantly improves the constraints on the retrieved parameters of the dust content. We confirm the result from previous studies that including a young stellar population in the modelling is important to explain the observed stellar energy distribution. However, the discrepancy between the observed and modelled thermal emission at far-infrared wavelengths, the so-called dust energy balance problem, is still present: the model underestimates the observed fluxes by a factor of about two. We compare two different dust models, and find that dust parameters, and thus the spectral energy distribution in the infrared domain, are sensitive to the adopted dust model. In general, the THEMIS model reproduces the observed emission in the infrared wavelength domain better than the popular BARE-GR-S model. Our study of IC2531 is a pilot case for detailed and uniform radiative transfer modelling of the entire HEROES sample, which will shed more light on the strength and origins of the dust energy balance problem.
We present simultaneous measurements of emission from dust continuum at 230 GHz and the J=2-1 \(^{12}\)CO, \(^{13}\)CO and C\(^{18}\)O isotopologues at \(\sim\) 15 pc resolution from individual Giant ...Molecular Clouds (GMCs) in the Andromeda galaxy (M31). These observations were obtained in an ongoing survey of this galaxy being conducted with the Submillimeter Array (SMA). Initial results describing the continuum and \(^{12}\)CO emission were published earlier. Here we primarily analyze the observations of \(^{13}\)CO and C\(^{18}\)O emission and compare them to the measurements of dust continuum and \(^{12}\)CO emission. We also report additional dust continuum and CO measurements from newly added GMCs to the M31 sample. We detect spatially resolved \(^{13}\)CO emission with high signal-to-noise in 31 objects. We find the extent of the \(^{13}\)CO emission to be nearly comparable to that of \(^{12}\)CO, typically covering 75\% of the area of the \(^{12}\)CO emission. We derive \(^{13}\)CO and C\(^{18}\)O abundances of 2.9 \(\times 10^{-6}\) and 4.4 \(\times 10^{-7}\) relative to H\(_2\), respectively, by comparison with hydrogen column densities of the same regions derived from the dust continuum observations assuming a Milky Way gas-to-dust ratio. We find the isotopic abundance ratio \(^{13}\)CO/C\(^{18}\)O = 6.7\(\pm\)2.9 to be consistent with the Milky Way value (8.1). Finally, we derive the mass-to-light conversion factors for all three CO species to be \(\alpha_{12} = 8.7 \pm 3.9\), \(\alpha_{13} = 48.9 \pm 20.4\) and \(\alpha_{18} = 345^{+25}_{-31}\) M\(_\odot\) (K km s\(^{-1}\)pc\(^2\))\(^{-1}\) for the J=2-1 transitions of \(^{12}\)CO, \(^{13}\)CO and C\(^{18}\)O, respectively.
The Herschel Virgo Cluster Survey Pappalardo, Ciro; Bizzocchi, Luca; Fritz, Jacopo ...
Astronomy and astrophysics (Berlin),
2016, Letnik:
589
Journal Article
Recenzirano
Context. The star formation rate is a crucial parameter for the investigation galaxy evolution. At low redshift the cosmic star formation rate density declines smoothly, and massive active galaxies ...become passive, reducing their star formation activity. This implies that the bulk of the star formation rate density at low redshift is mainly driven by low mass objects. Aims. We investigate the properties of a sample of low luminosity far-infrared sources selected at 250 μm. We have collected data from ultraviolet to far-infrared in order to perform a multiwavelengths analysis. The main goal is to investigate the correlation between star formation rate, stellar mass, and dust mass for a galaxy population with a wide range in dust content and stellar mass, including the low mass regime that most probably dominates the star formation rate density at low redshift. Methods. We define a main sample of ~800 sources with full spectral energy distribution coverage between 0.15 <λ< 500 μm and an extended sample with ~5000 sources in which we remove the constraints on the ultraviolet and near-infrared bands. We analyze both samples with two different spectral energy distribution fitting methods: MAGPHYS and CIGALE, which interpret a galaxy spectral energy distribution as a combination of different simple stellar population libraries and dust emission templates. Results. In the star formation rate versus stellar mass plane our samples occupy a region included between local spirals and higher redshift star forming galaxies. These galaxies represent the population that at z< 0.5 quenches their star formation activity and reduces their contribution to the cosmic star formation rate density. The subsample of galaxies with the higher masses (M∗> 3 × 1010 M⊙) do not lie on the main sequence, but show a small offset as a consequence of the decreased star formation. Low mass galaxies (M∗< 1 × 1010 M⊙) settle in the main sequence with star formation rate and stellar mass consistent with local spirals. Conclusions. Deep Herschel data allow the identification of a mixed galaxy population with galaxies still in an assembly phase or galaxies at the beginning of their passive evolution. We find that the dust luminosity is the parameter that allow us to discriminate between these two galaxy populations. The median spectral energy distribution shows that even at low star formation rate our galaxy sample has a higher mid-infrared emission than previously predicted.
In our local Galactic neighborhood, molecular clouds are best studied using a combination of dust measurements, to determine robust masses, sizes and internal structures of the clouds, and ...molecular-line observations to determine cloud kinematics and chemistry. We present here the first results of a program designed to extend such studies to nearby galaxies beyond the Magellanic Clouds. Utilizing the wideband upgrade of the Submillimeter Array (SMA) at 230 GHz we have obtained the first continuum detections of the thermal dust emission on sub-GMC scales (\(\sim\) 15 pc) within the Andromeda galaxy (M31). These include the first resolved continuum detections of dust emission from individual GMCs beyond the Magellanic Clouds. Utilizing a powerful capability of the SMA, we simultaneously recorded CO(2-1) emission with identical \((u,\,v)\) coverage, astrometry and calibration, enabling the first measurements of the CO conversion factor, \(\alpha_{\rm\,CO(2-1)}\), toward individual GMCs across an external galaxy. Our direct measurement yields an average CO--to--dust mass conversion factor of \(\alpha^\prime_{\rm CO-dust} = 0.042\pm0.018\) \(M_\odot\) (K km s\(^{-1}\) pc\(^2\))\(^{-1}\) for the \(J= 2-1\) transition. This value does not appear to vary with galactocentric radius. Assuming a constant gas-to-dust ratio of 136, the resulting \(\alpha_{\rm CO}\) \(=\) 5.7 \(\pm\) 2.4 \(M_\odot\) (K km s\(^{-1}\) pc\(^2\))\(^{-1}\) for the 2-1 transition is in excellent agreement with that of Milky Way GMCs, given the uncertainties. Finally, using the same analysis techniques, we compare our results with observations of the local Orion molecular clouds, placed at the distance of M31 and simulated to appear as they would if observed by the SMA.
The Herschel Virgo Cluster Survey Pappalardo, Ciro; Bendo, George J.; Bianchi, Simone ...
Astronomy and astrophysics (Berlin),
01/2015, Letnik:
573
Journal Article
Recenzirano
Aims. We present three independent catalogs of point-sources extracted from SPIRE images at 250, 350, and 500 μm, acquired with the Herschel Space Observatory as a part of the Herschel Virgo Cluster ...Survey (HeViCS). The catalogs have been cross-correlated to consistently extract the photometry at SPIRE wavelengths for each object. Methods. Sources have been detected using an iterative loop. The source positions are determined by estimating the likelihood to be a real source for each peak on the maps, according to the criterion defined in the sourceExtractorSussextractor task. The flux densities are estimated using the sourceExtractorTimeline, a timeline-based point source fitter that also determines the fitting procedure with the width of the Gaussian that best reproduces the source considered. Afterwards, each source is subtracted from the maps, removing a Gaussian function in every position with the full width half maximum equal to that estimated in sourceExtractorTimeline. This procedure improves the robustness of our algorithm in terms of source identification. We calculate the completeness and the flux accuracy by injecting artificial sources in the timeline and estimate the reliability of the catalog using a permutation method. Results. The HeViCS catalogs contain about 52 000, 42 200, and 18 700 sources selected at 250, 350, and 500 μm above 3σ and are ~75%, 62%, and 50% complete at flux densities of 20 mJy at 250, 350, 500 μm, respectively. We then measured source number counts at 250, 350, and 500 μm and compare them with previous data and semi-analytical models. We also cross-correlated the catalogs with the Sloan Digital Sky Survey to investigate the redshift distribution of the nearby sources. From this cross-correlation, we select ~2000 sources with reliable fluxes and a high signal-to-noise ratio, finding an average redshift z ~ 0.3 ± 0.22 and 0.25 (16–84 percentile). Conclusions. The number counts at 250, 350, and 500 μm show an increase in the slope below 200 mJy, indicating a strong evolution in number of density for galaxies at these fluxes. In general, models tend to overpredict the counts at brighter flux densities, underlying the importance of studying the Rayleigh-Jeans part of the spectral energy distribution to refine the theoretical recipes of the models. Our iterative method for source identification allowed the detection of a family of 500 μm sources that are not foreground objects belonging to Virgo and not found in other catalogs.
One of the most important properties of a galaxy is the total stellar mass, or equivalently the stellar mass-to-light ratio (M/L). It is not directly observable, but can be estimated from stellar ...population synthesis. Currently, a galaxy's M/L is typically estimated from global fluxes. For example, a single global g - i colour correlates well with the stellar M/L. Spectral energy distribution (SED) fitting can make use of all available fluxes and their errors to make a Bayesian estimate of the M/L. We want to investigate the possibility of using morphology information to assist predictions of M/L. Our first goal is to develop and train a method that only requires a g-band image and redshift as input. This will allows us to study the correlation between M/L and morphology. Next, we can also include the i-band flux, and determine if morphology provides additional constraints compared to a method that only uses g- and i-band fluxes. We used a machine learning pipeline that can be split in two steps. First, we detected morphology features with a convolutional neural network. These are then combined with redshift, pixel size and g-band luminosity features in a gradient boosting machine. Our training target was the M/L acquired from the GALEX-SDSS-WISE Legacy Catalog, which uses global SED fitting and contains galaxies with z ~ 0.1. Morphology is a useful attribute when no colour information is available, but can not outperform colour methods on its own. When we combine the morphology features with global g- and i-band luminosities, we find an improved estimate compared to a model which does not make use of morphology. While our method was trained to reproduce global SED fitted M/L, galaxy morphology gives us an important additional constraint when using one or two bands. Our framework can be extended to other problems to make use of morphological information.
In this work, we characterise 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 characterised 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 RT modelling. 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 (\(\sim\)80% at 10 \(\mu\)m to \(\sim\)50% at 1 mm). We find that the local dust-energy balance is restored at spatial scales greater than around 1.5 kpc.
We characterize the ionized gas outflows in 15 low-redshift star-forming galaxies, a Valparaíso ALMA Line Emission Survey (VALES) subsample, using MUSE integral field spectroscopy and GAMA ...photometric broadband data. We measure the emission-line spectra by fitting a double-component profile, with the second and broader component being related to the outflowing gas. This interpretation is in agreement with the correlation between the observed star-formation rate surface density (\(\Sigma_{\mathrm{SFR}}\)) and the second-component velocity dispersion (\(\sigma_{\mathrm{2nd}}\)), expected when tracing the feedback component. By modelling the broadband spectra with spectra energy distribution (SED) fitting and obtaining the star-formation histories of the sample, we observe a small decrease in SFR between 100 and 10 Myr in galaxies when the outflow H\(\alpha\) luminosity contribution is increased, indicating that the feedback somewhat inhibits the star formation within these timescales. The observed emission-line ratios are best reproduced by photoionization models when compared to shock-ionization, indicating that radiation from young stellar population is dominant, and seems to be a consequence of a continuous star-formation activity instead of a bursty event. The outflow properties such as mass outflow rate (\(\sim 0.1\,\)M\(_\odot\) yr\(^{-1}\)), outflow kinetic power (\(\sim 5.2 \times 10^{-4}\% L_{\mathrm{bol}}\)) and mass loading factor (\(\sim 0.12\)) point towards a scenario where the measured feedback is not strong and has a low impact on the evolution of galaxies in general.
We present the first nonparametric morphological analysis of a set of spiral galaxies from UV to submm wavelengths. Our study is based on high-quality multi-wavelength imaging for nine well-resolved ...spiral galaxies from the DustPedia database, combined with nonparametric morphology indicators calculated in a consistent way using the {\tt{StatMorph}} package. We measure the half-light radius, the concentration index, the asymmetry index, the smoothness index, the Gini coefficient and the \(M_{20}\) indicator in various wavebands from UV to submm wavelengths, as well as in stellar mass, dust mass and star formation rate maps. We find that the interstellar dust in galaxies is distributed in a more extended, less centrally concentrated, more asymmetric, and more clumpy way than the stars. This is particularly evident when comparing morphological indicators based on the stellar mass and dust mass maps. This should serve as a warning sign against treating the dust in galaxies as a simple smooth component. We argue that the nonparametric galaxy morphology of galaxies from UV to submm wavelengths is an interesting test for cosmological hydrodynamics simulations.
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