arXiv subjects

F. van der Tak

Publications and source records attributed to F. van der Tak.

At least 19 recordsLinked to original sources

arXiv2026

ALMAGAL IX. The chemical complexity of AG318.9477-00.1960: A line-identification template for ALMAGAL

We present a detailed molecular line analysis of one of the most chemically rich cores in the ALMAGAL sample, the high-mass core~9 in the AG318.9477-00.1960 clump (AG318-c9), located at a heliocentric distance of \sim 10.4\,\rm kpc. We further assessed whether the emission of selected COMs, that is, ethylene glycol ((CH_2OH)_2; EG), glycolaldehyde (CH_2(OH)CHO; GA), and methyl formate (CH_3OCHO; MF), can be used to trace the innermost regions of hot molecular cores (HMCs). We analysed ALMA Band~6 observations (\sim 217-221GHz). Spectral line identification and local thermodynamic equilibrium modelling were performed using the software MADCUBA. We derived the physical parameters, including the column density (N), excitation temperature (Tex), velocity, line width, and molecular abundances relative to H_2, for all detected species. The chemical inventory of AG318-c9 was compared with that of the HMC G31.41+0.31 (G31). In addition, we performed a pixel-by-pixel analysis of EG, GA, and MF to generate spatially resolved N and Tex maps and corresponding radial profiles.

astro-ph.GA↗

arXiv2026

ALMAGAL VI. The spatial distribution of dense cores during the evolution of cluster-forming massive clump

High-mass stars and star clusters form from the fragmentation of massive dense clumps driven by gravity, turbulence, and magnetic fields. The ALMAGAL project observed $\sim1000$ clumps at $\sim$1000\,au resolution, enabling a statistically significant characterization of this process across a large range of clump physical parameters and evolutionary stages. In this work, we investigated the spatial distribution of dense cores in the 514 massive, potentially cluster-forming, clumps hosting at least 4 cores, to trace fragmentation's initial conditions and early evolution. We used quantitative descriptors, evaluated against the clump bolometric luminosity-to-mass ratio as an indicator of evolution. Core separations were measured with the minimum spanning tree method (MST) and compared with the Jeans gravitational fragmentation theory. We used the $Q$ parameter and the mass segregation ratio, $Λ_{MSR}$, to evaluate whether cores have specific arrangements or differences depending on their masses. ALMAGAL cores are usually arranged in elliptical groups with an axis ratio $e\sim2.2$, but $e\geq$5 is also observed. A single characteristic core separation per clump is found in $\sim76$% of cases, but signatures of multiple fragmentation lengths not rare. Typical core separations are compatible with the clump-averaged thermal Jeans length, $λ^{th}_{J}$, though a population, typical of low-fragmented/young clumps, has wider separations with $l\approx3\timesλ^{th}_{J}$. The core separation decreases on average from $l\sim22000$ au in younger systems to $l\sim7000$ au in more evolved ones. Cores are typically distributed in fractal-type subclusters, with centrally concentrated patterns appearing only at later stages, but without a progressive evolutionary transition. Finally, mass segregation is found in 110 systems, with its occurrence increasing with evolution.

astro-ph.GA↗

arXiv2025

ALMAGAL V. Relations between the core populations and the parent clump physical properties

Context. The fragmentation of massive molecular clumps into smaller, potentially star-forming cores plays a key role in the processes of high-mass star formation. The ALMAGAL project offers high-resolution data to investigate these processes across various evolutionary stages in the Galactic plane. Aims. This study aims at correlating the fragmentation properties of massive clumps, obtained from ALMA observations, with their global physical parameters (e.g., mass, surface density, and temperature) and evolutionary indicators (such as luminosity-to-mass ratio and bolometric temperature) obtained from Herschel observations. It seeks to assess whether the cores evolve in number and mass in tandem with their host clumps, and to determine the possible factors influencing the formation of massive cores (M > 24M_\odot). Methods. We analyzed the masses of 6348 fragments, estimated from 1.4 mm continuum data for 1007 ALMAGAL clumps. Leveraging this unprecedentedly large data set, we evaluated statistical relationships between clump parameters, estimated over about 0.1 pc scales, and fragment properties, corresponding to scales of a few 1000 au, while accounting for potential biases related to distance and observational resolution. Our results were further compared with predictions from numerical simulations. Results. The fragmentation level correlates preferentially with clump surface density, supporting a scenario of density-driven fragmentation, whereas it does not show any clear dependence on total clump mass. Both the mass of the most massive core and the core formation efficiency show a broad range and increase on average by an order of magnitude in the intervals spanned by evolutionary indicators such as clump dust temperature and the luminosity-to-mass ratio. This suggests that core growth continues throughout the clump evolution, favoring clump-fed over core-fed theoretical scenarios.

astro-ph.GA↗

arXiv2025

ALMAGAL I. The ALMA evolutionary study of high-mass protocluster formation in the Galaxy. Presentation of the survey and early results

Fundamental questions about the physics responsible for fragmenting molecular parsec-scale clumps into cores of ~1000 au are still open, that only a statistically significant investigation with ALMA is able to address: what are the dominant agents that determine the core demographics, mass, and spatial distribution as a function of the physical properties of the hosting clumps, their evolutionary stage and the different Galactic environments in which they reside? To what extent extent is fragmentation driven by clumps dynamics or mass transport in filaments? With ALMAGAL we observed the 1.38 mm continuum and lines toward more than 1000 dense clumps in our Galaxy, with M>500M_sun, surface density > 0.1 g/cm2 and d<7.5 kpc. The ACA and two 12-m array setups were used to deliver a minimum resolution of ~1000 au over the entire sample distance range. The sample covers all evolutionary stages from infrared dark clouds (IRDCs) to HII regions from the tip of the Galactic bar to the outskirts of the Galaxy. The spectral setup includes several molecular lines to trace the multiscale physics and dynamics of gas, notably CH3CN, H2CO, SiO, CH3OH, DCN, HC3N, SO etc. We present an initial overview of the observations and the early science product and results, with a first characterization of the morphological properties of the continuum emission. We use "perimeter-versus-area" and convex hull-versus-area metrics to classify the different morphologies. More extended and morphologically complex shapes are found toward clumps that are relatively more evolved and have higher surface densities.

astro-ph.GA↗

arXiv2025

ALMAGAL III. Compact source catalog: Fragmentation statistics and physical evolution of the core population

The mechanisms behind the fragmentation of high-mass dense clumps into compact star-forming cores are fundamental topics in current astrophysical research. The ALMAGAL survey provides the opportunity to study this process at an unprecedented level of detail and statistical significance, featuring high-angular resolution $1.38$ mm ALMA observations of $1013$ massive dense clumps at various Galactic locations. These clumps cover a wide range of distances, masses, surface densities, and evolutionary stages. Here, we present the catalog of compact sources obtained with the CuTEx algorithm from continuum images of the full ALMAGAL clump sample combining ACA-$7$m and $12$m ALMA arrays, reaching a uniform high median spatial resolution of $\sim1400$ au. We discuss the fragmentation properties and the estimated physical parameters of the core population. The ALMAGAL compact source catalog includes $6348$ cores detected in $844$ clumps ($83\%$ of the total), with a number of cores per clump between $1$ and $49$ (median of $5$). The estimated core diameters are mostly within $\sim800-3000$ au (median of $1700$ au). We obtained core masses from $0.002$ to $345\,\mathrm{M_{\odot}}$. We evaluated the variation in the core mass function (CMF) with evolution as traced by the clump $L/M$, finding a clear, robust shift and change in slope among CMFs within subsamples at different stages. This finding suggests that the CMF shape is not constant throughout the star formation process, but rather it builds (and flattens) with evolution, with higher core masses reached at later stages. We found that all cores within a clump grow in mass on average with evolution, and the number of cores increases with the core masses. Our results favor a clump-fed scenario for high-mass star formation, in which cores form as low-mass seeds, and then gain mass while further fragmentation occurs in the clump.

astro-ph.GA↗

arXiv2024

Dynamical Accretion Flows -- ALMAGAL: Flows along filamentary structures in high-mass star-forming clusters

We use data from the ALMA Evolutionary Study of High Mass Protocluster Formation in the Galaxy (ALMAGAL) survey to study 100 ALMAGAL regions at $\sim$ 1 arsecond resolution located between $\sim$ 2 and 6 kpc distance. Using ALMAGAL $\sim$ 1.3mm line and continuum data we estimate flow rates onto individual cores. We focus specifically on flow rates along filamentary structures associated with these cores. Our primary analysis is centered around position velocity cuts in H$_2$CO (3$_{0,3}$ - 2$_{0,2}$) which allow us to measure the velocity fields, surrounding these cores. Combining this work with column density estimates we derive the flow rates along the extended filamentary structures associated with cores in these regions. We select a sample of 100 ALMAGAL regions covering four evolutionary stages from quiescent to protostellar, Young Stellar Objects (YSOs), and HII regions (25 each). Using dendrogram and line analysis, we identify a final sample of 182 cores in 87 regions. In this paper, we present 728 flow rates for our sample (4 per core), analysed in the context of evolutionary stage, distance from the core, and core mass. On average, for the whole sample, we derive flow rates on the order of $\sim$10$^{-4}$ M$_{sun}$yr$^{-1}$ with estimated uncertainties of $\pm$50%. We see increasing differences in the values among evolutionary stages, most notably between the less evolved (quiescent/protostellar) and more evolved (YSO/HII region) sources. We also see an increasing trend as we move further away from the centre of these cores. We also find a clear relationship between the flow rates and core masses $\sim$M$^{2/3}$ which is in line with the result expected from the tidal-lobe accretion mechanism. Overall, we see increasing trends in the relationships between the flow rate and the three investigated parameters; evolutionary stage, distance from the core, and core mass.

astro-ph.GA↗

arXiv2023

Tracing Evolution in Massive Protostellar Objects (TEMPO) -- I: Fragmentation and emission properties of massive star-forming clumps in a luminosity limited ALMA sample

The role of massive ($\geq$ 8M$_{\odot}$) stars in defining the energy budget and chemical enrichment of the interstellar medium in their host galaxy is significant. In this first paper from the Tracing Evolution in Massive Protostellar Objects (TEMPO) project we introduce a colour-luminosity selected (L$_*$ $\sim$ 3$\times10^3$ to 1$\times10^5$ L$_{\odot}$) sample of 38 massive star forming regions observed with ALMA at 1.3mm and explore the fragmentation, clustering and flux density properties of the sample. The TEMPO sample fields are each found to contain multiple fragments (between 2-15 per field). The flux density budget is split evenly (53%-47%) between fields where emission is dominated by a single high flux density fragment and those in which the combined flux density of fainter objects dominates. The fragmentation scales observed in most fields are not comparable with the thermal Jeans length, $λ_J$, being larger in the majority of cases, suggestive of some non-thermal mechanism. A tentative evolutionary trend is seen between luminosity of the clump and the `spectral line richness' of the TEMPO fields; with 6.7GHz maser associated fields found to be lower luminosity and more line rich. This work also describes a method of line-free continuum channel selection within ALMA data and a generalised approach used to distinguishing sources which are potentially star-forming from those which are not, utilising interferometric visibility properties.

astro-ph.GA↗

arXiv2022

The sharp ALMA view of infall and outflow in the massive protocluster G31.41+0.31

Context. To better understand the formation of high-mass stars, it is fundamental to investigate how matter accretes onto young massive stars, how it is ejected, and how all this differs from the low-mass case. The massive protocluster G31.41+0.31 is the ideal target to study all these processes because observations at millimeter and centimeter wavelengths have resolved the emission of the Main core into at least four massive dust continuum sources, named A, B, C, and D, within 1" or 0.018 pc, and have identified signatures of infall and several outflows associated with the core. Aims. We study the interplay between infall and outflow in G31.41+0.31 by investigating at a spatial resolution of a few 100 au their properties and their possible impact on the core. Methods. We carried out molecular line observations of typical high-density tracers, such as CH3CN or H2CO, and shock and outflow tracers, such as SiO, with ALMA at 1.4 mm that achieved an angular resolution of 0.09" (340 au). Results. The observations have revealed inverse P-Cygni profiles in CH3CN and H2CO toward the four sources embedded in the Main core, suggesting that all of them are undergoing collapse. The infall rates, estimated from the red-shifted absorption are on the order of 1E-2 Msun/yr. The individual infall rates imply that the accretion timescale of the Main core is an order of magnitude smaller than its rotation timescale. This confirms that rotating toroids such as the G31 Main core are non-equilibrium, transient collapsing structures that need to be constantly replenished with fresh material from a large-scale reservoir. For sources B, C, and D, the infall could be accelerating inside the sources, while for source A, the presence of a second emission component complicates the interpretation. The SiO observations have revealed the presence of at least six outflows in the G31.41+0.31 star-forming region, ...

astro-ph.GA↗

arXiv2021

Interrelations between Astrochemistry and Galactic Dynamics

This paper presents a review of ideas that interconnect Astrochemistry and Galactic Dynamics. Since these two areas are vast and not recent, each one has already been covered separately by several reviews. After a general historical introduction, and a needed quick review of processes like the stellar nucleosynthesis which gives the base to understand the interstellar formation of simple chemical compounds (H2, CO, NH3 and H2O), we focus on a number of topics which are at the crossing of the two areas, Dynamics and Astrochemistry. Astrochemistry is a flourishing field which intends to study the presence and formation of molecules as well as the influence of them into the structure, evolution and dynamics of astronomical objects. The progress in the knowledge on the existence of new complex molecules and of their process of formation originates from the observational, experimental and theoretical areas which compose the field. The interfacing areas include star formation, protoplanetary disks, the role of the spiral arms and the chemical abundance gradients in the galactic disk. It often happens that the physical conditions in some regions of the ISM are only revealed by means of molecular observations. To organise a classification of chemical evolution processes, we discuss about how astrochemistry can act in three different contexts: i. the chemistry of the early universe, including external galaxies, ii. star forming regions, and iii. AGB stars and circumstellar envelopes. We mention that our research is stimulated by plans for instruments and projects, such as the on-going LLAMA, which consists in the construction of a 12m sub-mm radio telescope in the Andes. Thus, modern and new facilities can play a key role in new discoveries not only in astrochemistry but also in radio astronomy and related areas. Furthermore, the research of the origin of life is also a stimulating perspective.

astro-ph.GA↗

arXiv2021

Fragmentation in the massive G31.41+0.31 protocluster

Context. ALMA observations at 1.4 mm and 0.2'' (750au) angular resolution of the Main core in the high-mass star forming region G31.41+0.31 have revealed a puzzling scenario: on the one hand, the continuum emission looks very homogeneous and the core appears to undergo solid-body rotation, suggesting a monolithic core stabilized by the magnetic field; on the other hand, rotation and infall speed up toward the core center, where two massive embedded free-free continuum sources have been detected, pointing to an unstable core having undergone fragmentation. Aims. To establish whether the Main core is indeed monolithic or its homogeneous appearance is due to a combination of large dust opacity and low angular resolution, we carried out millimeter observations at higher angular resolution and different wavelengths. Methods. We carried out ALMA observations at 1.4 mm and 3.5 mm that achieved angular resolutions of 0.1''(375 au) and 0.075'' (280 au), respectively. VLA observations at 7 mm and 1.3 cm at even higher angular resolution, 0.05'' (190 au) and 0.07'' (260 au), respectively, were also carried out to better study the nature of the free-free continuum sources detected in the core. Results. The millimeter continuum emission of the Main core has been clearly resolved into at least four sources, A, B, C, and D, within 1'', indicating that the core is not monolithic. The deconvolved radii of the dust emission of the sources, estimated at 3.5 mm, are 400-500au, their masses range from 15 to 26 Msun, and their number densities are several 1E9 cm-3. Sources A and B, located closer to the center of the core and separated by 750 au, are clearly associated with two free-free continuum sources, likely thermal radio jets, and are the brightest in the core. The spectral energy distribution of these two sources and their masses and sizes are similar and suggest a common origin.

astro-ph.GA↗

arXiv2019

Probing the cold magnetized Universe with SPICA-POL (B-BOP)

SPICA, the cryogenic infrared space telescope recently pre-selected for a `Phase A' concept study as one of the three remaining candidates for ESA's fifth medium class (M5) mission, is foreseen to include a far-infrared polarimetric imager (SPICA-POL, now called B-BOP), which would offer a unique opportunity to resolve major issues in our understanding of the nearby, cold magnetized Universe. This paper presents an overview of the main science drivers for B-BOP, including high dynamic range polarimetric imaging of the cold interstellar medium (ISM) in both our Milky Way and nearby galaxies. Thanks to a cooled telescope, B-BOP will deliver wide-field 100-350 micron images of linearly polarized dust emission in Stokes Q and U with a resolution, signal-to-noise ratio, and both intensity and spatial dynamic ranges comparable to those achieved by Herschel images of the cold ISM in total intensity (Stokes I). The B-BOP 200 micron images will also have a factor ~30 higher resolution than Planck polarization data. This will make B-BOP a unique tool for characterizing the statistical properties of the magnetized interstellar medium and probing the role of magnetic fields in the formation and evolution of the interstellar web of dusty molecular filaments giving birth to most stars in our Galaxy. B-BOP will also be a powerful instrument for studying the magnetism of nearby galaxies and testing galactic dynamo models, constraining the physics of dust grain alignment, informing the problem of the interaction of cosmic rays with molecular clouds, tracing magnetic fields in the inner layers of protoplanetary disks, and monitoring accretion bursts in embedded protostars.

astro-ph.GA↗

arXiv2018

Accelerating infall and rotational spin-up in the hot molecular core G31.41+0.31

As part of our effort to search for circumstellar disks around high-mass stellar objects, we observed the well-known core G31.41+0.31 with ALMA at 1.4 mm with an angular resolution of~0.22" (~1700 au). The dust continuum emission has been resolved into two cores namely Main and NE. The Main core, which has the stronger emission and is the more chemically rich, has a diameter of ~5300 au, and is associated with two free-free continuum sources. The Main core looks featureless and homogeneous in dust continuum emission and does not present any hint of fragmentation. Each transition of CH3CN and CH3OCHO, both ground and vibrationally excited, as well as those of CH3CN isotopologues, shows a clear velocity gradient along the NE-SW direction, with velocity linearly increasing with distance from the center, consistent with solid-body rotation. However, when comparing the velocity field of transitions with different upper level energies, the rotation velocity increases with increasing energy of the transition, which suggests that the rotation speeds up towards the center. Spectral lines towards the dust continuum peak show an inverse P-Cygni profile that supports the existence of infall in the core. The infall velocity increases with the energy of the transition suggesting that the infall is accelerating towards the center of the core, consistent with gravitational collapse. Despite the monolithic appearance of the Main core, the presence of red-shifted absorption, the existence of two embedded free-free sources at the center, and the rotational spin-up are consistent with an unstable core undergoing fragmentation with infall and differential rotation due to conservation of angular momentum. Therefore, the most likely explanation for the monolithic morphology is that the large opacity of the dust emission prevents the detection of any inhomogeneity in the core.

astro-ph.SR↗

arXiv2017

Unbiased large spectroscopic surveys of galaxies selected by SPICA using dust bands

The mid-infrared (IR) range contains many spectral features associated with large molecules and dust grains such as polycyclic aromatic hydrocarbons (PAHs) and silicates. These are usually very strong compared to fine-structure gas lines, and thus valuable in studying the spectral properties of faint distant galaxies. In this paper, we evaluate the capability of low-resolution mid-IR spectroscopic surveys of galaxies that could be performed by SPICA. The surveys are designed to address the question how star formation and black hole accretion activities evolved over cosmic time through spectral diagnostics of the physical conditions of the interstellar/circumnuclear media in galaxies. On the basis of results obtained with Herschel far-IR photometric surveys of distant galaxies and Spitzer and AKARI near- to mid-IR spectroscopic observations of nearby galaxies, we estimate the numbers of the galaxies at redshift z > 0.5, which are expected to be detected in the PAH features or dust continuum by a wide (10 deg^2) or deep (1 deg^2) blind survey, both for a given observation time of 600 hours. As by-products of the wide blind survey, we also expect to detect debris disks, through the mid-IR excess above the photospheric emission of nearby main-sequence stars, and we estimate their number. We demonstrate that the SPICA mid-IR surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-IR with SPICA.

astro-ph.GA↗

arXiv2017

Feedback and feeding in the context of galaxy evolution with SPICA: direct characterization of molecular outflows and inflows

A far-infrared observatory such as the {\it SPace Infrared telescope for Cosmology and Astrophysics} ({\it SPICA}), with its unprecedented spectroscopic sensitivity, would unveil the role of feedback in galaxy evolution during the last $\sim10$ Gyr of the Universe ($z=1.5-2$), through the use of far- and mid-infrared molecular and ionic fine structure lines that trace outflowing and infalling gas. Outflowing gas is identified in the far-infrared through P-Cygni line shapes and absorption blueshifted wings in molecular lines with high dipolar moments, and through emission line wings of fine-structure lines of ionized gas. We quantify the detectability of galaxy-scale massive molecular and ionized outflows as a function of redshift in AGN-dominated, starburst-dominated, and main-sequence galaxies, explore the detectability of metal-rich inflows in the local Universe, and describe the most significant synergies with other current and future observatories that will measure feedback in galaxies via complementary tracers at other wavelengths.

astro-ph.GA↗

arXiv2017

Tracing the evolution of dust obscured star-formation and accretion back to the reionisation epoch with SPICA

Our current knowledge of star formation and accretion luminosity at high-redshift (z>3-4), as well as the possible connections between them, relies mostly on observations in the rest-frame ultraviolet (UV), which are strongly affected by dust obscuration. Due to the lack of sensitivity of past and current infrared (IR) instrumentation, so far it has not been possible to get a glimpse into the early phases of the dust-obscured Universe. Among the next generation of IR observatories, SPICA, observing in the 12-350 micron range, will be the only facility that can enable us to make the required leap forward in understanding the obscured star-formation rate and black-hole accretion rate densities (SFRD and BHARD, respectively) with respect to what Spitzer and Herschel achieved in the mid- and far-IR at z<3. In particular, SPICA will have the unique ability to trace the evolution of the obscured SFRD and BHARD over cosmic time, from the peak of their activity back to the reionisation epoch (i.e., 3<z<6-7), where its predecessors had severe limitations. Here we discuss the potential of both deep and shallow photometric surveys performed with the SPICA mid-IR instrument (SMI), enabled by the very low level of impact of dust obscuration in a band centred at 34 micron. These unique unbiased photometric surveys that SPICA will perform will be followed up by observations both with the SPICA spectrometers and with other facilities at shorter and longer wavelengths, with the aim to fully characterise the evolution of AGNs and star-forming galaxies after re-ionisation.

astro-ph.GA↗

arXiv2017

SPICA and the Chemical Evolution of Galaxies: The Rise of Metals and Dust

The physical processes driving the chemical evolution of galaxies in the last $\sim 11\, \rm{Gyr}$ cannot be understood without directly probing the dust-obscured phase of star-forming galaxies and active galactic nuclei. This phase, hidden to optical tracers, represents the bulk of star formation and black hole accretion activity in galaxies at $1 < z < 3$. Spectroscopic observations with a cryogenic infrared (IR) observatory like SPICA will be sensitive enough to peer through the dust-obscured regions of galaxies and access the rest-frame mid- to far-IR range in galaxies at high-$z$. This wavelength range contains a unique suite of spectral lines and dust features that serve as proxies for the abundances of heavy elements and the dust composition, providing tracers with a feeble response to both extinction and temperature. In this work, we investigate how SPICA observations could be exploited to understand key aspects in the chemical evolution of galaxies: the assembly of nearby galaxies based on the spatial distribution of heavy element abundances, the global content of metals in galaxies reaching the knee of the luminosity function up to $z \sim 3$, and the dust composition of galaxies at high-$z$. Possible synergies with facilities available in the late 2020s are also discussed.

astro-ph.GA↗

arXiv2017

Galaxy evolution studies with the SPace IR telescope for Cosmology and Astrophysics (SPICA): the power of IR spectroscopy

IR spectroscopy in the range 12-230 micron with the SPace IR telescope for Cosmology and Astrophysics (SPICA) will reveal the physical processes that govern the formation and evolution of galaxies and black holes through cosmic time, bridging the gap between the James Webb Space Telescope (JWST) and the new generation of Extremely Large Telescopes (ELTs) at shorter wavelengths and the Atacama Large Millimeter Array (ALMA) at longer wavelengths. SPICA, with its 2.5-m telescope actively-cooled to below 8K, will obtain the first spectroscopic determination, in the mid-IR rest-frame, of both the star-formation rate and black hole accretion rate histories of galaxies, reaching lookback times of 12 Gyr, for large statistically significant samples. Densities, temperatures, radiation fields and gas-phase metallicities will be measured in dust-obscured galaxies and active galactic nuclei (AGN), sampling a large range in mass and luminosity, from faint local dwarf galaxies to luminous quasars in the distant Universe. AGN and starburst feedback and feeding mechanisms in distant galaxies will be uncovered through detailed measurements of molecular and atomic line profiles. SPICA's large-area deep spectrophotometric surveys will provide mid-IR spectra and continuum fluxes for unbiased samples of tens of thousands of galaxies, out to redshifts of z~6. Furthermore, SPICA spectroscopy will uncover the most luminous galaxies in the first few hundred million years of the Universe, through their characteristic dust and molecular hydrogen features.

astro-ph.GA↗

arXiv2017

Distribution of water in the G327.3-0.6 massive star-forming region

We aim at characterizing the large-scale distribution of H2O in G327.3-0.6, a massive star-forming region made of individual objects in different evolutionary phases. We investigate variations of H2O abundance as function of evolution. We present Herschel continuum maps at 89 and 179 $μ$m of the whole region and an APEX map at 350 μm of the IRDC. New spectral HIFI maps toward the IRDC region covering low-energy H2O lines at 987 and 1113 GHz are also presented and combined with HIFI pointed observations of the G327 hot core. We infer the physical properties of the gas through optical depth analysis and radiative transfer modeling. The continuum emission at 89 and 179 μm follows the thermal continuum emission at longer wavelengths, with a peak at the position of the hot core, a secondary peak in the Hii region, and an arch-like layer of hot gas west of the Hii region. The same morphology is observed in the 1113 GHz line, in absorption toward all dust condensations. Optical depths of ~80 and 15 are estimated and correspond to column densities of 10^15 and 2 10^14 cm-2, for the hot core and IRDC position. These values indicate an H2O to H2 ratio of 3 10^-8 toward the hot core; the abundance of H2O does not change along the IRDC with values of some 10^-8. Infall (over ~ 20") is detected toward the hot core position with a rate of 1-1.3 10^-2 M_sun /yr, high enough to overcome the radiation pressure due to the stellar luminosity. The source structure of the hot core region is complex, with a cold outer gas envelope in expansion, situated between the outflow and the observer, extending over 0.32 pc. The outflow is seen face-on and centered away from the hot core. The distribution of H2O along the IRDC is roughly constant with an abundance peak in the more evolved object. These water abundances are in agreement with previous studies in other massive objects and chemical models.

astro-ph.GA↗