ABSTRACT Molecular snow lines in protoplanetary disks have been studied theoretically for decades because of their importance in shaping planetary architectures and compositions. The water snow line ...lies in the planet formation region at 10 AU, and so far its location has been estimated only indirectly from spatially unresolved spectroscopy. This work presents a proof-of-concept method to directly image the water snow line in protoplanetary disks through its physical and chemical imprint on the local dust properties. We adopt a physical disk model that includes dust coagulation, fragmentation, drift, and a change in fragmentation velocities of a factor of 10 between dry silicates and icy grains as found by laboratory work. We find that the presence of a water snow line leads to a sharp discontinuity in the radial profile of the dust emission spectral index mm due to replenishment of small grains through fragmentation. We use the ALMA simulator to demonstrate that this effect can be observed in protoplanetary disks using spatially resolved ALMA images in two continuum bands. We explore the model dependence on the disk viscosity and find that the spectral index reveals the water snow line for a wide range of conditions, with opposite trends when the emission is optically thin rather than thick. If the disk viscosity is low ( visc < 10−3), the snow line produces a ringlike structure with a minimum at mm ∼ 2 in the optically thick regime, possibly similar to what has been measured with ALMA in the innermost region of the HL Tau disk.
We have fit the far-ultraviolet (FUV) to sub-millimeter (850 μm) spectral energy distributions (SEDs) of the 61 galaxies from the Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel ...(KINGFISH). The fitting has been performed using three models: the Code for Investigating GALaxy Evolution (CIGALE), the GRAphite-SILicate approach (GRASIL), and the Multiwavelength Analysis of Galaxy PHYSical properties (MAGPHYS). We have analyzed the results of the three codes in terms of the SED shapes, and by comparing the derived quantities with simple “recipes” for stellar mass (Mstar), star-formation rate (SFR), dust mass (Mdust), and monochromatic luminosities. Although the algorithms rely on different assumptions for star-formation history, dust attenuation and dust reprocessing, they all well approximate the observed SEDs and are in generally good agreement for the associated quantities. However, the three codes show very different behavior in the mid-infrared regime: in the 5–10 μm region dominated by PAH emission, and also between 25 and 70 μm where there are no observational constraints for the KINGFISH sample. We find that different algorithms give discordant SFR estimates for galaxies with low specific SFR, and that the standard recipes for calculating FUV absorption overestimate the extinction compared to the SED-fitting results. Results also suggest that assuming a “standard” constant stellar mass-to-light ratio overestimates Mstar relative to the SED fitting, and we provide new SED-based formulations for estimating Mstar from WISE W1 (3.4 μm) luminosities and colors. From a principal component analysis of Mstar, SFR, Mdust, and O/H, we reproduce previous scaling relations among Mstar, SFR, and O/H, and find that Mdust can be predicted to within ∼0.3 dex using only Mstar and SFR.
The acyclic nucleoside phosphonate cidofovir (CDV) and its closely related analogue (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)-adenine (S-HPMPA) have been reported to have activity against many ...adenovirus (AdV) serotypes. A new series of orally active ether lipid-ester prodrugs of CDV and of (S)-HPMPA that have slight differences in the structure of their lipid esters were evaluated, in tissue-culture cells, for activity against 5 AdV serotypes. The results indicated that, against several AdV serotypes, the most active compounds were 15-2500-fold more active than the unmodified parent compounds and should be evaluated further for their potential to treat AdV infections in humans.
Context. Measuring how the physical properties of galaxies change across cosmic times is essential to understand galaxy formation and evolution. With the advent of numerous ground-based and ...space-borne instruments launched over the past few decades we now have exquisite multi-wavelength observations of galaxies from the far-ultraviolet (FUV) to the radio domain. To tap into this mine of data and obtain new insight into the formation and evolution of galaxies, it is essential that we are able to extract information from their spectral energy distribution (SED). Aims. We present a completely new implementation of Code Investigating GALaxy Emission (CIGALE). Written in python, its main aims are to easily and efficiently model the FUV to radio spectrum of galaxies and estimate their physical properties such as star formation rate, attenuation, dust luminosity, stellar mass, and many other physical quantities. Methods. To compute the spectral models, CIGALE builds composite stellar populations from simple stellar populations combined with highly flexible star formation histories, calculates the emission from gas ionised by massive stars, and attenuates both the stars and the ionised gas with a highly flexible attenuation curve. Based on an energy balance principle, the absorbed energy is then re-emitted by the dust in the mid- and far-infrared domains while thermal and non-thermal components are also included, extending the spectrum far into the radio range. A large grid of models is then fitted to the data and the physical properties are estimated through the analysis of the likelihood distribution. Results. CIGALE is a versatile and easy-to-use tool that makes full use of the architecture of multi-core computers, building grids of millions of models and analysing samples of thousands of galaxies, both at high speed. Beyond fitting the SEDs of galaxies and parameter estimations, it can also be used as a model-generation tool or serve as a library to build new applications.
Context. Over the past few years the Atacama Large Millimeter Array (ALMA) has detected dust-rich galaxies whose cold dust emission is spatially disconnected from the ultraviolet (UV) rest-frame ...emission. This represents a challenge for modeling their spectral energy distributions (SED) with codes based on an energy budget between the stellar and dust components. This could potentially weaken the solidity of the physical parameters measured with these modeling tools. Aims. We want to verify the validity of energy balance modeling on a sample of galaxies observed from the UV to the sub-millimeter rest frame with ALMA and decipher what information can be reliably retrieved from the analysis of the full SED and from subsets of wavelengths. Methods. We select 17 sources at z ≃ 2 in the Hubble Ultra-Deep Field (HUDF) and in the GOODS-South field detected with ALMA and Herschel and for which UV to near-infrared rest-frame ancillary data are available. We fit the data with CIGALE exploring different configurations for dust attenuation and star formation histories, considering either the full dataset or one that is reduced to the stellar and dust emission. We compare estimates of the dust luminosities, star formation rates, and stellar masses. Results. The fit of the stellar continuum alone with the starburst attenuation law can only reproduce up to 50% of the total dust luminosity observed by Herschel and ALMA. This deficit is found to be marginally consistent with similar quantities estimated in the COSMOS field and is found to increase with the specific star formation rate. The combined stellar and dust SEDs are well fitted when different attenuation laws are introduced. Shallow attenuation curves are needed for the galaxies whose cold dust distribution is very compact compared to starlight. The stellar mass estimates are affected by the choice of the attenuation law. The star formation rates are robustly estimated as long as dust luminosities are available. The large majority of the galaxies are above the average main sequence of star forming galaxies and one source is a strong starburst.
Aims. We use high-resolution continuum images obtained with the Atacama Large Millimeter Array (ALMA) to probe the surface density of star formation in z ~ 2 galaxies and study the different physical ...properties between galaxies within and above the star-formation main sequence of galaxies. Methods. We use ALMA images at 870 μm with 0.2 arcsec resolution in order to resolve star formation in a sample of eight star-forming galaxies at z ~ 2 selected among the most massive Herschel galaxies in the GOODS-South field. This sample is supplemented with eleven galaxies from the public data of the 1.3 mm survey of the Hubble Ultra-Deep Field, HUDF. We derive dust and gas masses for the galaxies, compute their depletion times and gas fractions, and study the relative distributions of rest-frame ultraviolet (UV) and far-infrared (FIR) light. Results. ALMA reveals systematically dense concentrations of dusty star formation close to the center of the stellar component of the galaxies. We identify two different starburst regimes: (i) the classical population of starbursts located above the SFR-M⋆ main sequence, with enhanced gas fractions and short depletion times and (ii) a sub-population of galaxies located within the scatter of the main sequence that experience compact star formation with depletion timescales typical of starbursts of ~150 Myr. In both starburst populations, the FIR and UV are distributed in distinct regions and dust-corrected star formation rates (SFRs) estimated using UV-optical-near-infrared data alone underestimate the total SFR. Starbursts hidden in the main sequence show instead the lowest gas fractions of our sample and could represent the last stage of star formation prior to passivization. Being Herschel-selected, these main sequence galaxies are located in the high-mass end of the main sequence, hence we do not know whether these “starbursts hidden in the main sequence” also exist below 1011 M⊙. Active galactic nuclei (AGNs) are found to be ubiquitous in these compact starbursts, suggesting that the triggering mechanism also feeds the central black hole or that the active nucleus triggers star formation.
We use X-ray active galactic nuclei (AGN) observed by the
Chandra
X-ray Observatory within the 9.3 deg
2
Boötes field of the NDWFS to study whether there is a correlation between X-ray luminosity (
L
...X
) and star formation rate (SFR) of the host galaxy, at 0.5 <
z
< 2.0, with respect to the position of the galaxy to the main sequence (SFR
norm
). About half of the sources in the X-ray sample have spectroscopic redshifts. We also construct a reference galaxy catalogue. For both datasets we use photometric data from the optical to the far-infrared compiled by the HELP project, and apply spectral energy distribution fitting, using the X-CIGALE code. We exclude quiescent sources from both the X-ray and the reference samples. We also account for the mass completeness of our dataset, in different redshifts bins. Our analysis highlights the importance of studying the SFR–
L
X
relation in a uniform manner, taking into account systematics and selection effects. Our results suggest, in less massive galaxies (log
M
*
(
M
⊙
) ∼ 11), that an AGN enhances the SFR of the host galaxy by ∼50% compared to non-AGN systems. A flat relation is observed for the most massive galaxies. The SFR
norm
does not evolve with redshift. The results, although tentative, are consistent with a scenario where, in less massive systems, both AGN and star formation are fed by cold gas supplied by a merger event. In more massive galaxies the flat relation could be explained by a different supermasssive black hole fuelling mechanism that is decoupled from the star formation of the host galaxy (e.g., hot diffuse gas). Finally, we compare the host galaxy properties of X-ray absorbed and unabsorbed sources. Our results show no difference, which suggests that X-ray absorption is not linked with the properties of the galaxy.
Submillimeter/millimeter observations of dusty star-forming galaxies with the Atacama Large Millimeter/submillimeter Array (ALMA) have shown that dust continuum emission generally occurs in compact ...regions smaller than the stellar distribution. However, it remains to be understood how systematic these findings are. Studies often lack homogeneity in the sample selection, target discontinuous areas with inhomogeneous sensitivities, and suffer from modest
u
v
coverage coming from single array configurations. GOODS-ALMA is a 1.1 mm galaxy survey over a continuous area of 72.42 arcmin
2
at a homogeneous sensitivity. In this version 2.0, we present a new low resolution dataset and its combination with the previous high resolution dataset from the survey, improving the
u
v
coverage and sensitivity reaching an average of
σ
= 68.4 μJy beam
−1
. A total of 88 galaxies are detected in a blind search (compared to 35 in the high resolution dataset alone), 50% at
S
/
N
peak
≥ 5 and 50% at 3.5 ≤
S
/
N
peak
≤ 5 aided by priors. Among them, 13 out of the 88 are optically dark or faint sources (
H
- or
K
-band dropouts). The sample dust continuum sizes at 1.1 mm are generally compact, with a median effective radius of
R
e
= 0
.
″
10 ± 0
.
″
05 (a physical size of
R
e
= 0.73 ± 0.29 kpc at the redshift of each source). Dust continuum sizes evolve with redshift and stellar mass resembling the trends of the stellar sizes measured at optical wavelengths, albeit a lower normalization compared to those of late-type galaxies. We conclude that for sources with flux densities
S
1.1 mm
> 1 mJy, compact dust continuum emission at 1.1 mm prevails, and sizes as extended as typical star-forming stellar disks are rare. The
S
1.1 mm
< 1 mJy sources appear slightly more extended at 1.1 mm, although they are still generally compact below the sizes of typical star-forming stellar disks.
Abstract
We search for passive galaxies at z > 3 in the GOODS-South field, using different techniques based on photometric data, and paying attention to develop methods that are sensitive to objects ...that have become passive shortly before the epoch of observation. We use CANDELS HST catalogues, ultra-deep Ks data and new IRAC photometry, performing spectral energy distribution fitting using models with abruptly quenched star formation histories. We then single out galaxies which are best fitted by a passively evolving model, and having only low probability (<5 per cent) star-forming solutions. We verify the effects of including nebular lines emission, and we consider possible solutions at different redshifts. The number of selected sources dramatically depends on the models used in the spectral energy distribution (SED) fitting. Without including emission lines and with photometric redshifts fixed at the CANDELS estimate, we single out 30 candidates; the inclusion of nebular lines emission reduces the sample to 10 objects; allowing for solutions at different redshifts, only two galaxies survive as robust candidates. Most of the candidates are not far-infrared emitters, corroborating their association with passive galaxies. Our results translate into an upper limit in the number density of ∼0.173 arcmin2 above the detection limit. However, we conclude that the selection of passive galaxies at z > 3 is still subject to significant uncertainties, being sensitive to assumptions in the SED modelling adopted and to the relatively low S/N of the objects. By means of dedicated simulations, we show that JWST will greatly enhance the accuracy, allowing for a much more robust classification.
We investigate the properties of a sample of 35 galaxies, detected with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 1.1 mm in the GOODS-ALMA field (area of 69 arcmin
2
, resolution = ...0.60″, rms ≃ 0.18 mJy beam
−1
). Using the ultraviolet-to-radio deep multiwavelength coverage of the GOODS–South field, we fit the spectral energy distributions of these galaxies to derive their key physical properties. The galaxies detected by ALMA are among the most massive at
z
= 2−4 (
M
⋆, med
= 8.5 × 10
10
M
⊙
) and they are either starburst or located in the upper part of the galaxy star-forming main sequence. A significant portion of our galaxy population (∼40%), located at
z
∼ 2.5 − 3, exhibits abnormally low gas fractions. The sizes of these galaxies, measured with ALMA, are compatible with the trend between the rest-frame 5000 Å size and stellar mass observed for
z
∼ 2 elliptical galaxies, suggesting that they are building compact bulges. We show that there is a strong link between star formation surface density (at 1.1 mm) and gas depletion time: The more compact a galaxy’s star-forming region is, the shorter its lifetime will be (without gas replenishment). The identified compact sources associated with relatively short depletion timescales (∼100 Myr) are the ideal candidates to be the progenitors of compact elliptical galaxies at
z
∼ 2.
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