Showing papers by "F. F. S. van der Tak published in 2017"
INAF1, University of Cologne2, University of Leeds3, Leiden University4, Max Planck Society5, University of Hamburg6, University of Manchester7, National Autonomous University of Mexico8, Radboud University Nijmegen9, UK Astronomy Technology Centre10, University of Tübingen11, University of Hertfordshire12, University of Porto13, European Southern Observatory14, Indian Institute of Space Science and Technology15, Dublin Institute for Advanced Studies16, Ames Research Center17
TL;DR: In this paper, the authors used the H2020 Marie Sklodowska-Curie Action (GESTATE 661249) funded by the European Research Commission (ERC).
Abstract: This work is supported by a H2020 Marie Sklodowska-Curie Action (GESTATE 661249) funded by the European Research Commission. Reproduced with permission from Astronomy & Astrophysics. © 2017 ESO. Published by EDP Sciences.
97 citations
TL;DR: In this article, the chemical makeup of several hot molecular cores was investigated to determine physical and chemical structure of high-mass star formation, using high spectral and spatial resolution sub-millimeter observations to determine how this stage fits into the formation sequence of a highmass star.
Abstract: Context. In the study of high-mass star formation, hot cores are empirically defined stages where chemically rich emission is detected toward a massive YSO. It is unknown whether the physical origin of this emission is a disk, inner envelope, or outflow cavity wall and whether the hot core stage is common to all massive stars.Aims. We investigate the chemical makeup of several hot molecular cores to determine physical and chemical structure. We use high spectral and spatial resolution submillimeter observations to determine how this stage fits into the formation sequence of a high-mass star.Methods. The submillimeter interferometer ALMA (Atacama Large Millimeter Array) was used to observe the G35.20-0.74N and G35.03+0.35 hot cores at 350 GHz in Cycle 0. We analyzed spectra and maps from four continuum peaks (A, B1, B2 and B3) in G35.20-0.74N, separated by 1000–2000 AU, and one continuum peak in G35.03+0.35. We made all possible line identifications across 8 GHz of spectral windows of molecular emission lines down to a 3σ line flux of 0.5 K and determined column densities and temperatures for as many as 35 species assuming local thermodynamic equilibrium (LTE).Results. In comparing the spectra of the four continuum peaks, we find each has a distinct chemical composition expressed in over 400 different transitions. In G35.20, B1 and B2 contain oxygen- and sulfur-bearing organic and inorganic species but few nitrogen-bearing species whereas A and B3 are strong sources of O-, S-, and N-bearing organic and inorganic species (especially those with the CN bond). Column densities of vibrationally excited states are observed to be equal to or greater than the ground state for a number of species. Deuterated methyl cyanide is clearly detected in A and B3 with D/H ratios of 8 and 13%, respectively, but is much weaker at B1 and undetected at B2. No deuterated species are detected in G35.03, but similar molecular abundances to G35.20 were found in other species. We also find co-spatial emission of isocyanic acid (HNCO) and formamide (NH2 CHO) in both sources indicating a strong chemical link between the two species.Conclusions. The chemical segregation between N-bearing organic species and others in G35.20 suggests the presence of multiple protostars surrounded by a disk or torus.
42 citations
TL;DR: In this paper, the physical and chemical structure of the prototypical high UV-illumination edge on Orion Bar PDR from an unbiased spectral line survey with a wide spectral coverage was presented.
Abstract: Context. Photon dominated regions (PDRs) are interfaces between the mainly ionized and mainly molecular material around young massive stars. Analysis of the physical and chemical structure of such regions traces the impact of far-ultraviolet radiation of young massive stars on their environment.Aims. We present results on the physical and chemical structure of the prototypical high UV-illumination edge-on Orion Bar PDR from an unbiased spectral line survey with a wide spectral coverage which includes lines of many important gas coolants such as [Cii], [Ci], and CO and other key molecules such as H2 CO, H2 O, HCN, HCO+ , and SO.Methods. A spectral scan from 480–1250 GHz and 1410–1910 GHz at 1.1 MHz resolution was obtained by the HIFI instrument on board the Herschel Space Observatory. We obtained physical parameters for the observed molecules. For molecules with multiple transitions we used rotational diagrams to obtain excitation temperatures and column densities. For species with a single detected transition we used an optically thin LTE approximation. In the case of species with available collisional rates, we also performed a non-LTE analysis to obtain kinetic temperatures, H2 volume densities, and column densities.Results. About 120 lines corresponding to 29 molecules (including isotopologues) have been detected in the Herschel /HIFI line survey, including 11 transitions of CO, 7 transitions of 13 CO, 6 transitions of C18 O, 10 transitions of H2 CO, and 6 transitions of H2 O. The rotational temperatures are in the range between ~22 and ~146 K and the column densities are in the range between 1.8 × 1012 cm-2 and 4.5 × 1017 cm-2 . For species with at least three detected transitions and available collisional excitation rates we derived a best fit kinetic temperature and H2 volume density. Most species trace kinetic temperatures in the range between 100 and 150 K and H2 volume densities in the range between 105 and 106 cm-3 . The species with temperatures and/or densities outside this range include the H2 CO transitions tracing a very high temperature (315 K) and density (1.4 × 106 cm-3 ) component and SO corresponding to the lowest temperature (56 K) measured as a part of this line survey.Conclusions. The observed lines/species reveal a range of physical conditions (gas density/temperature) involving structures at high density/high pressure, making the traditional clump/interclump picture of the Orion Bar obsolete.
38 citations
TL;DR: In this paper, the velocity-resolved Herschel-HIFI observations of the ortho-NH3(10 - 00) line at 572 GHz were used to study the abundance profile of ammonia across the pre-stellar core L1544.
Abstract: Pre-stellar cores represent the initial conditions in the process of star and planet formation, therefore it is important to study their physical and chemical structure. Because of their volatility, nitrogen-bearing molecules are key to study the dense and cold gas present in pre-stellar cores. The NH3 rotational transition detected with Herschel-HIFI provides a unique combination of sensitivity and spectral resolution to further investigate physical and chemical processes in pre-stellar cores. Here we present the velocity-resolved Herschel-HIFI observations of the ortho-NH3(10 - 00) line at 572 GHz and study the abundance profile of ammonia across the pre-stellar core L1544 to test current theories of its physical and chemical structure. Recently calculated collisional coefficients have been included in our non-LTE radiative transfer code to reproduce Herschel observations. A gas-grain chemical model, including spin-state chemistry and applied to the (static) physical structure of L1544 is also used to infer the abundance profile of ortho-NH3. The hyperfine structure of ortho-NH3(10 - 00) is resolved for the first time in space. All the hyperfine components are strongly self-absorbed. The profile can be reproduced if the core is contracting in quasi-equilibrium, consistent with previous work, and if the NH3 abundance is slightly rising toward the core centre, as deduced from previous interferometric observations of para-NH3(1, 1). The chemical model overestimates the NH3 abundance at radii between ≃4000 and 15 000 AU by about two orders of magnitude and underestimates the abundance toward the core centre by more than one order of magnitude. Our observations show that chemical models applied to static clouds have problems in reproducing NH3 observations. Based on observations carried out with Herschel, an ESA space observatory with science instruments provided by a European-led Principal Investigator consortium and with important participation from NASA.
34 citations
TL;DR: In this article, the velocity-resolved Herschel-HIFI observations of the ortho-NH_3(1_0-0_0) line at 572 GHz were used to study the abundance profile of ammonia across the pre-stellar core L1544 to test current theories of its physical and chemical structure.
Abstract: Pre-stellar cores represent the initial conditions in the process of star and planet formation, therefore it is important to study their physical and chemical structure. Because of their volatility, nitrogen-bearing molecules are key to study the dense and cold gas present in pre-stellar cores. The NH_3 rotational transition detected with Herschel-HIFI provides a unique combination of sensitivity and spectral resolution to further investigate physical and chemical processes in pre-stellar cores. Here we present the velocity-resolved Herschel-HIFI observations of the ortho-NH_3(1_0-0_0) line at 572 GHz and study the abundance profile of ammonia across the pre-stellar core L1544 to test current theories of its physical and chemical structure.
Recently calculated collisional coefficients have been included in our non-LTE radiative transfer code to reproduce Herschel observations. A gas-grain chemical model, including spin-state chemistry and applied to the (static) physical structure of L1544 is also used to infer the abundance profile of ortho-NH_3 . The hyperfine structure of ortho-NH_3(1_0-0_0) is resolved for the first time in space. All the hyperfine components are strongly self-absorbed. The profile can be reproduced if the core is contracting in quasi-equilibrium, consistent with previous work, and if the NH_3 abundance is slightly rising toward the core centre, as deduced from previous interferometric observations of para-NH_3(1,1). The chemical model overestimates the NH_3 abundance at radii between ~ 4000 and 15000 AU by about two orders of magnitude and underestimates the abundance toward the core centre by more than one order of magnitude. Our observations show that chemical models applied to static clouds have problems in reproducing NH_3 observations.
33 citations
INAF1, Spanish National Research Council2, California Institute of Technology3, Ghent University4, Open University5, University of Maryland, College Park6, Centre national de la recherche scientifique7, Paris Diderot University8, Imperial College London9, University of La Laguna10, University of Tokyo11, European University Cyprus12, University of Arizona13, United States Naval Research Laboratory14, University of Padua15, University of Toulouse16, University of Alcalá17, Institut d'Astrophysique de Paris18, European Southern Observatory19, Nagoya University20, Tokyo Institute of Technology21, Japan Aerospace Exploration Agency22, University of California, Los Angeles23, Cardiff University24, Osaka University25, Ehime University26, University of Cambridge27, University of Bologna28, University of Geneva29, Sapienza University of Rome30, University of British Columbia31, University of Toledo32, Max Planck Society33, Royal Institute of Technology34
TL;DR: The SPACE IR telescope for Cosmology and Astrophysics (SPICA) as discussed by the authors was used to study the formation and evolution of galaxies and black holes through cosmic time, bridging the gap between the James Webb Space Telescope and the upcoming Extremely Large Telescopes at shorter wavelengths and the Atacama Large Millimeter Array at longer wavelengths.
Abstract: IR spectroscopy in the range 12–230 μm with the SPace IR telescope for Cosmology and Astrophysics (SPICA) will reveal the physical processes governing the formation and evolution of galaxies and black holes through cosmic time, bridging the gap between the James Webb Space Telescope and the upcoming Extremely Large Telescopes at shorter wavelengths and the Atacama Large Millimeter Array at longer wavelengths. The SPICA, with its 2.5-m telescope actively cooled to below 8 K, 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, sampling a large range in mass and luminosity, from faint local dwarf galaxies to luminous quasars in the distant Universe. Active galactic nuclei and starburst feedback and feeding mechanisms in distant galaxies will be uncovered through detailed measurements of molecular and atomic line profiles. The 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.
31 citations
TL;DR: In this article, high-resolution ALMA observations of nine HII regions selected from the Red MSX Source (RMS) survey with compact radio emission and bolometric luminosities greater than 10$^4$ L$_\odot$ were presented.
Abstract: High-mass stars form in much richer environments than those associated with isolated low-mass stars, and once they reach a certain mass, produce ionised (HII) regions. The formation of these pockets of ionised gas are unique to the formation of high-mass stars (M $>8$ M$_\odot$), and present an excellent opportunity to study the final stages of accretion, which could include accretion through the HII region itself. This study of the dynamics of the gas on both sides of these ionisation boundaries in very young HII regions aims to quantify the relationship between the HII regions and their immediate environments.We present high-resolution ($\sim$ 0.5$"$) ALMA observations of nine HII regions selected from the Red MSX Source (RMS) survey with compact radio emission and bolometric luminosities greater than 10$^4$ L$_\odot$. We focus on the initial presentation of the data, including initial results from the radio recombination line H29$\alpha$, some complementary molecules, and the 256 GHz continuum emission. Of the six (out of nine) regions with H29$\alpha$ detections, two appear to have cometary morphologies with velocity gradients across them, and two appear more spherical with velocity gradients suggestive of infalling ionised gas. The remaining two were either observed at low resolution or had signals that were too weak to draw robust conclusions. We also present a description of the interactions between the ionised and molecular gas (as traced by CS (J=5-4)), often (but not always) finding theHII region had cleared its immediate vicinity of molecules. Of our sample of nine, the observations of the two clusters expected to have the youngest HII regions (from previous radio observations) are suggestive of having infalling motions in the H29$\alpha$ emission, which could be indicative of late stage accretion onto the stars despite the presence of an HII region.
26 citations
Centre national de la recherche scientifique1, University of Alberta2, University of Antofagasta3, University of Massachusetts Amherst4, King Abdulaziz University5, Max Planck Society6, Leiden University7, Australia Telescope National Facility8, Tata Institute of Fundamental Research9, University of La Laguna10, Spanish National Research Council11, University of Cologne12, Kapteyn Astronomical Institute13, Netherlands Institute for Space Research14
TL;DR: In this article, the authors used a sophisticated Bayesian formalism to derive the most likely values for each of the parameters mentioned above as a function of position in the nearby prototypical low metallicity (12 + log log O/H) ~ 8.4) spiral galaxy M 33.
Abstract: Do some environments favor efficient conversion of molecular gas into stars? To answer this, we need to be able to estimate the H2 mass. Traditionally, this is done using CO observations and a few assumptions but the Herschel observations which cover the far-IR dust spectrum make it possible to estimate the molecular gas mass independently of CO and thus to investigate whether and how the CO traces H2 . Previous attempts to derive gas masses from dust emission suffered from biases. Generally, dust surface densities, H i column densities, and CO intensities are used to derive a gas-to-dust ratio (GDR) and the local CO intensity to H2 column density ratio (X CO ), sometimes allowing for an additional CO-dark gas component (K dark ). We tested earlier methods, revealing degeneracies among the parameters, and then used a sophisticated Bayesian formalism to derive the most likely values for each of the parameters mentioned above as a function of position in the nearby prototypical low metallicity (12 + log (O/H) ~ 8.4) spiral galaxy M 33. The data are from the IRAM Large Program mapping in the CO(2–1) line along with high-resolution H i and Herschel dust continuum observations. Solving for GDR, X CO , and K dark in macropixels 500 pc in size, each containing many individual measurements of the CO, H i, and dust emission, we find that (i) allowing for CO dark gas (K dark ) significantly improves fits; (ii) K dark decreases with galactocentric distance; (iii) GDR is slightly higher than initially expected and increases with galactocentric distance; (iv) the total amount of dark gas closely follows the radially decreasing CO emission, as might be expected if the dark gas is H2 where CO is photodissociated. The total amount of H2 , including dark gas, yields an average X CO of twice the galactic value of 2 × 1020 cm-2 / K km s-1 , with about 55% of this traced directly through CO. The rather constant fraction of dark gas suggests that there is no large population of diffuse H2 clouds (unrelated to GMCs) without CO emission. Unlike in large spirals, we detect no systematic radial trend in X CO , possibly linked to the absence of a radial decrease in CO line ratios.
25 citations
INAF1, Paris Diderot University2, European Southern Observatory3, University of Padua4, California Institute of Technology5, Ghent University6, Imperial College London7, European University Cyprus8, Spanish National Research Council9, University of La Laguna10, University of Arizona11, University of Alcalá12, Cardiff University13, Nagoya University14, Open University15, University of the Western Cape16, University of Trieste17, Japan Aerospace Exploration Agency18, University of Tokyo19, Rutherford Appleton Laboratory20, Complutense University of Madrid21, University of British Columbia22, Netherlands Institute for Space Research23
TL;DR: In this paper, the authors discuss the potential of photometric surveys performed with the SPICA mid-infrared instrument, enabled by the very low level of impact of dust obscuration in a band centred at 34 µm.
Abstract: 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, which are strongly affected by dust obscuration. Due to the lack of sensitivity of past and current infrared 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 infrared observatories, SPICA, observing in the 12–350 µm range, will be the only facility that can enable us to trace the evolution of the obscured star-formation rate and black-hole accretion rate densities 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 photometric surveys performed with the SPICA mid-infrared instrument, enabled by the very low level of impact of dust obscuration in a band centred at 34 µm. These unique unbiased photometric surveys that SPICA will perform will fully characterise the evolution of AGNs and star-forming galaxies after reionisation.
24 citations
TL;DR: In this article, the spectral energy distributions (SEDs) were used to create Gaussian prior estimates in the SPIRE bands for XID+ and the extracted SPIRE flux densities were run through CIGALE again to compare the performance of the two priors.
Abstract: Aims: Cosmological surveys in the far-infrared are known to suffer from confusion. The Bayesian de-blending tool, XID+, currently provides one of the best ways to de-confuse deep Herschel SPIRE images, using a flat flux density prior. This work is to demonstrate that existing multi-wavelength data sets can be exploited to improve XID+ by providing an informed prior, resulting in more accurate and precise extracted flux densities. Methods: Photometric data for galaxies in the COSMOS field were used to constrain spectral energy distributions (SEDs) using the fitting tool CIGALE. These SEDs were used to create Gaussian prior estimates in the SPIRE bands for XID+. The multi-wavelength photometry and the extracted SPIRE flux densities were run through CIGALE again to allow us to compare the performance of the two priors. Inferred ALMA flux densities (FinferALMA), at 870 μm and 1250 μm, from the best fitting SEDs from the second CIGALE run were compared with measured ALMA flux densities (FmeasALMA) as an independent performance validation. Similar validations were conducted with the SED modelling and fitting tool MAGPHYS and modified black-body functions to test for model dependency. Results: We demonstrate a clear improvement in agreement between the flux densities extracted with XID+ and existing data at other wavelengths when using the new informed Gaussian prior over the original uninformed prior. The residuals between FmeasALMA and FinferALMA were calculated. For the Gaussian priors these residuals, expressed as a multiple of the ALMA error (σ), have a smaller standard deviation, 7.95σ for the Gaussian prior compared to 12.21σ for the flat prior; reduced mean, 1.83σ compared to 3.44σ; and have reduced skew to positive values, 7.97 compared to 11.50. These results were determined to not be significantly model dependent. This results in statistically more reliable SPIRE flux densities and hence statistically more reliable infrared luminosity estimates. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
23 citations
TL;DR: In the study of high-mass star formation, hot cores are empirically defined stages where chemically rich emission is detected toward a massive YSO It is unknown whether the physical origin of this emission is a disk, inner envelope, or outflow cavity wall and whether the hot core stage is common to all massive stars.
Abstract: In the study of high-mass star formation, hot cores are empirically defined stages where chemically rich emission is detected toward a massive YSO It is unknown whether the physical origin of this emission is a disk, inner envelope, or outflow cavity wall and whether the hot core stage is common to all massive stars We investigate the chemical make up of several hot molecular cores to determine physical and chemical structure We use high spectral and spatial resolution Cycle 0 ALMA observations to determine how this stage fits into the formation sequence of a high mass star We observed the G3520-074N and G3503+035 hot cores at 350 GHz We analyzed spectra and maps from four continuum peaks (A, B1, B2 and B3) in G3520, separated by 1000-2000 AU, and one continuum peak in G3503 We made all possible line identifications across 8 GHz of spectral windows of molecular emission lines and determined column densities and temperatures for as many as 35 species assuming local thermodynamic equilibrium In comparing the spectra of the four peaks, we find each has a distinct chemical composition expressed in over 400 different transitions In G3520, B1 and B2 contain oxygen- and sulfur-bearing organic and inorganic species but few nitrogen-bearing species whereas A and B3 are strong sources of O, S, and N-bearing species (especially those with the CN-bond) CH$_2$DCN is clearly detected in A and B3 with D/H ratios of 8 and 13$\%$, respectively, but is much weaker at B1 and undetected at B2 No deuterated species are detected in G3503, but similar molecular abundances to G3520 were found in other species We also find co-spatial emission of HNCO and NH$_2$CHO in both sources indicating a strong chemical link between the two species The chemical segregation between N-bearing organic species and others in G3520 suggests the presence of multiple protostars, surrounded by a disk or torus
University of Alcalá1, California Institute of Technology2, Spanish National Research Council3, European University Cyprus4, University of Arizona5, University of La Laguna6, INAF7, United States Naval Research Laboratory8, European Southern Observatory9, National Institutes of Natural Sciences, Japan10, Japan Aerospace Exploration Agency11, Nagoya University12, Jagiellonian University13, University of California, Los Angeles14, University of Padua15, Cornell University16, Max Planck Society17, Netherlands Institute for Space Research18
TL;DR: In this article, the authors quantify the detectability of galaxy-scale massive molecular and ionised outflows as a function of redshift in AGN-dominated, starburst-dominated and main-sequence galaxies.
Abstract: A far-infrared observatory such as the SPace Infrared telescope for Cosmology and Astrophysics, with its unprecedented spectroscopic sensitivity, would unveil the role of feedback in galaxy evolution during the last ~10 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 ionised gas. We quantify the detectability of galaxy-scale massive molecular and ionised 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.
California Institute of Technology1, Ghent University2, Open University3, University of Maryland, College Park4, Centre national de la recherche scientifique5, Paris Diderot University6, University College London7, University of Arizona8, United States Naval Research Laboratory9, University of Toulouse10, University of Alcalá11, INAF12, Nagoya University13, University of California, Los Angeles14, Japan Aerospace Exploration Agency15, Cardiff University16, Ehime University17, Spanish National Research Council18, University of Tokyo19, University of Oxford20, University of La Laguna21, University of Toledo22
TL;DR: In this article, the authors investigated 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 ~ 3, and the dust composition of galaxies at high-z.
Abstract: The physical processes driving the chemical evolution of galaxies in the last ~ 11Gyr 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 the star formation and black hole accretion activity in galaxies at 1 < z < 3. Spectroscopic observations with a cryogenic infrared observatory like SPICA, will be sensitive enough to peer through the dust-obscured regions of galaxies and access the rest-frame mid- to far-infrared 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 ~ 3, and the dust composition of galaxies at high-z. Possible synergies with facilities available in the late 2020s are also discussed.
Nagoya University1, Japan Aerospace Exploration Agency2, California Institute of Technology3, Ghent University4, Polish Academy of Sciences5, European University Cyprus6, University of La Laguna7, INAF8, Spanish National Research Council9, Institute for the Physics and Mathematics of the Universe10, University of Alcalá11, Cardiff University12, Graduate University for Advanced Studies13, Subaru14, University of Tokyo15, University of Bologna16, University of British Columbia17, University of Toledo18, University of the Western Cape19
TL;DR: In this article, the authors evaluate the capability of low-resolution mid-infrared spectroscopic surveys of galaxies that could be performed by SPICA, and demonstrate that the SPICA midinfrared surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-Infrared with SPICA.
Abstract: The mid-infrared range contains many spectral features associated with large molecules and dust grains such as polycyclic aromatic hydrocarbons 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-infrared 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-infrared photometric surveys of distant galaxies and Spitzer and AKARI near- to mid-infrared 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 polycyclic aromatic hydrocarbon features or dust continuum by a wide (10 deg2) or deep (1 deg2) blind survey, both for a given observation time of 600 h. As by-products of the wide blind survey, we also expect to detect debris disks, through the mid-infrared excess above the photospheric emission of nearby main-sequence stars, and we estimate their number. We demonstrate that the SPICA mid-infrared surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-infrared with SPICA.
TL;DR: In this article, the authors 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 detectable 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.
Abstract: 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.
TL;DR: In this article, the authors derived empirical molecular abundance profiles for the observed species using the Monte Carlo radiative transfer code (RATRAN) and adopting a 1D dust density/temperature profile from the literature.
Abstract: Context. It is not well known what drives the chemistry of a protostellar envelope, in particular the role of the stellar mass and the protostellar outflows on the chemical enrichment of such environments.Aims. We study the chemical structure of the Class 0 protostellar envelope NGC 1333 IRAS 4A in order to (i) investigate the influence of the outflows on the chemistry; (ii) constrain the age of our studied object; (iii) compare it with a typical high–mass protostellar envelope.Methods. In our analysis we use JCMT line mapping (360–373 GHz) and HIFI pointed spectra (626.01–721.48 GHz). To study the influence of the outflow on the degree of deuteration, we compare JCMT maps of HCO+ and DCO+ with non-LTE (RADEX) models in a region that spatially covers the outflow activity of IRAS 4A. To study the envelope chemistry, we derive empirical molecular abundance profiles for the observed species using the Monte Carlo radiative transfer code (RATRAN) and adopting a 1D dust density/temperature profile from the literature. We use a combination of constant abundance profiles and abundance profiles that include jumps at two radii (T ~ 100 K or T ~ 30 K) to fit our observations. We compare our best–fit observed abundance profiles with the predictions from the time dependent gas grain chemical code (ALCHEMIC).Results. We detect CO, 13 CO, C18 O, CS, HCN, HCO+ , N2 H+ , H2 CO, CH3 OH, H2 O, H2 S, DCO+ , HDCO, D2 CO, SO, SO2 , SiO, HNC, CN, C2 H and OCS. We divide the detected lines in three groups based on their line profiles: a) broad emission (FWHM = 4–11 km s-1 ), b) narrow emission (FWHM ), and c) showing absorption features. The broad component is indicative of outflow activity, the narrow component arises from dynamically quiescent gas (i.e. envelope) and the absorption is a result of infall motions or the presence of foreground material. Our maps provide information about the spatial and velocity structure of many of the molecules mentioned above, including the deuterated species, making it possible to distinguish between envelope and outflow structures also spatially. The derived abundance profiles are based only on the narrow component (envelope) of the species and are reproduced by a 1D pseudo-time-dependent gas-grain chemical model for the outer envelope, with the exceptions of HCN, HNC, CN. These species along with the CO abundance require an enhanced UV field which points towards an outflow cavity. The abundances with respect to H2 are 1 to 2 orders of magnitude lower than those observed in the high mass protostellar envelope (AFGL 2591), while they are found to be similar within factors of a few when they are estimated with respect to CO. Differences in UV radiation intensity may also be responsible for such chemical differentiation, but temperature differences seem a more plausible explanation, especially the absence of a freeze–out zone in the high mass case. The CH3 OH modeled abundance profile points towards an age of ≥4 × 104 yr for IRAS 4A. The spatial distribution of H2 D+ differs from that of other deuterated species (i.e. DCO+ , HDCO and D2 CO), indicating an origin from a colder layer ( The observed abundances can be explained by passive heating towards the high mass protostellar envelope, while the presence of UV cavity channels become more important toward the low mass protostellar envelope (e.g. CO, HCO+ ).
01 Sep 2017
TL;DR: In this article, the carbon flux from impacts of asteroids and comets is estimated for the first time, assuming a carbon content of 10% (Flynn, 1996), which implies an IDP carbon flux of 0.07 − 0.3 × 10 6 kg/yr.
Abstract: Abstract Given rapid photodissociation and photodegradation, the recently discovered organics in the Martian subsurface and atmosphere were probably delivered in geologically recent times. Possible parent bodies are C-type asteroids, comets, and interplanetary dust particles (IDPs). The dust infall rate was estimated, using different methods, to be between 0.71 and 2.96 × 10 6 kg/yr (Nesvorny et al., 2011; Borin et al., 2017; Crismani et al., 2017); assuming a carbon content of 10% (Flynn, 1996), this implies an IDP carbon flux of 0.07 − 0.3 × 10 6 kg/yr. We calculate for the first time the carbon flux from impacts of asteroids and comets. To this end, we perform dynamical simulations of impact rates on Mars. We use the N-body integrator RMVS/Swifter to propagate the Sun and the eight planets from their current positions. We separately add comets and asteroids to the simulations as massless test particles, based on their current orbital elements, yielding Mars impact rates of 4.34 × 10 − 3 comets/Myr and 3.3 asteroids/Myr. We estimate the delivered amount of carbon using published carbon content values. In asteroids, only C types contain appreciable amounts of carbon. Given the absence of direct taxonomic information on the Mars impactors, we base ourselves on the measured distribution of taxonomic types in combination with dynamic models of the origin of Mars-crossing asteroids. We estimate the global carbon flux on Mars from cometary impacts to be ∼ 0.013 × 10 6 kg/yr within an order of magnitude, while asteroids deliver ∼ 0.05 × 10 6 kg/yr. These values correspond to ∼ 4 − 19 % and ∼ 17 − 71 % , respectively, of the IDP-borne carbon flux estimated by Nesvorny et al., Borin et al. and Crismani et al. Unlike the spatially homogeneous IDP infall, impact ejecta are distributed locally, concentrated around the impact site. We find organics from asteroids and comets to dominate over IDP-borne organics at distances up to 150 km from the crater center. Our results may be important for the interpretation of in situ detections of organics on Mars.
California Institute of Technology1, Ghent University2, Open University3, University of Maryland, College Park4, Centre national de la recherche scientifique5, Paris Diderot University6, University College London7, University of Arizona8, United States Naval Research Laboratory9, University of Toulouse10, University of Alcalá11, INAF12, Nagoya University13, University of California, Los Angeles14, Japan Aerospace Exploration Agency15, Cardiff University16, Ehime University17, Spanish National Research Council18, University of Tokyo19, University of Oxford20, University of La Laguna21, University of Toledo22
TL;DR: In this paper, the authors investigated 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-$z$.
Abstract: 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.
Netherlands Institute for Space Research1, California Institute of Technology2, Ghent University Hospital3, Open University4, University of Maryland, College Park5, Centre national de la recherche scientifique6, Imperial College London7, Heidelberg University8, INAF9, University of La Laguna10, Spanish National Research Council11, Cardiff University12, University of Alcalá13, ASTRON14, University of Victoria15, University of Paris16, Nagoya University17, Academia Sinica18, University College London19, Japan Aerospace Exploration Agency20, University of Tokyo21, Complutense University of Madrid22
TL;DR: The SPICA mid and far-infrared telescope as discussed by the authors has been proposed to provide a large suite of atomic and ionic fine-structure lines for large samples of galaxies to shed light on the origin of the observed spread in star formation rates within and between galaxies.
Abstract: The SPICA mid and far-infrared telescope will address fundamental issues in our understanding of star formation and ISM physics in galaxies. A particular hallmark of SPICA is the outstanding sensitivity enabled by the cold telescope, optimized detectors, and wide instantaneous bandwidth throughout the mid- and far-infrared. The spectroscopic, imaging and polarimetric observations that SPICA will be able to collect will help in clarifying the complex physical mechanisms which underlie the baryon cycle of galaxies. In particular: (i) The access to a large suite of atomic and ionic fine-structure lines for large samples of galaxies will shed light on the origin of the observed spread in star formation rates within and between galaxies. (ii) Observations of HD rotational lines (out to $\sim$10 Mpc) and fine structure lines such as [CII] 158 $\mu$m (out to $\sim$100 Mpc) will clarify the main reservoirs of interstellar matter in galaxies, including phases where CO does not emit. (iii) Far-infrared spectroscopy of dust and ice features will address uncertainties in the mass and composition of dust in galaxies, and the contributions of supernovae to the interstellar dust budget will be quantified by photometry and monitoring of supernova remnants in nearby galaxies. (iv) Observations of far-infrared cooling lines such as [OI] 63 $\mu$m from star-forming molecular clouds in our Galaxy will evaluate the importance of shocks to dissipate turbulent energy. The paper concludes with requirements for the telescope and instruments, and recommendations for the observing strategy.
01 Mar 2017
TL;DR: In this paper, the physical and chemical structure of the prototypical high UV-illumination edge on Orion Bar PDR from an unbiased spectral line survey with a wide spectral coverage was presented.
Abstract: Context. Photon dominated regions (PDRs) are interfaces between the mainly ionized and mainly molecular material around young massive stars. Analysis of the physical and chemical structure of such regions traces the impact of far-ultraviolet radiation of young massive stars on their environment. Aims. We present results on the physical and chemical structure of the prototypical high UV-illumination edge-on Orion Bar PDR from an unbiased spectral line survey with a wide spectral coverage which includes lines of many important gas coolants such as [Cii], [Ci], and CO and other key molecules such as H 2 CO, H 2 O, HCN, HCO + , and SO. Methods. A spectral scan from 480–1250 GHz and 1410–1910 GHz at 1.1 MHz resolution was obtained by the HIFI instrument on board the Herschel Space Observatory. We obtained physical parameters for the observed molecules. For molecules with multiple transitions we used rotational diagrams to obtain excitation temperatures and column densities. For species with a single detected transition we used an optically thin LTE approximation. In the case of species with available collisional rates, we also performed a non-LTE analysis to obtain kinetic temperatures, H 2 volume densities, and column densities. Results. About 120 lines corresponding to 29 molecules (including isotopologues) have been detected in the Herschel /HIFI line survey, including 11 transitions of CO, 7 transitions of 13 CO, 6 transitions of C 18 O, 10 transitions of H 2 CO, and 6 transitions of H 2 O. The rotational temperatures are in the range between ~22 and ~146 K and the column densities are in the range between 1.8 × 10 12 cm -2 and 4.5 × 10 17 cm -2 . For species with at least three detected transitions and available collisional excitation rates we derived a best fit kinetic temperature and H 2 volume density. Most species trace kinetic temperatures in the range between 100 and 150 K and H 2 volume densities in the range between 10 5 and 10 6 cm -3 . The species with temperatures and/or densities outside this range include the H 2 CO transitions tracing a very high temperature (315 K) and density (1.4 × 10 6 cm -3 ) component and SO corresponding to the lowest temperature (56 K) measured as a part of this line survey. Conclusions. The observed lines/species reveal a range of physical conditions (gas density/temperature) involving structures at high density/high pressure, making the traditional clump/interclump picture of the Orion Bar obsolete.
Abstract: Cosmological surveys in the far infrared are known to suffer from confusion. The Bayesian de-blending tool, XID+, currently provides one of the best ways to de-confuse deep Herschel SPIRE images, using a flat flux density prior. This work is to demonstrate that existing multi-wavelength data sets can be exploited to improve XID+ by providing an informed prior, resulting in more accurate and precise extracted flux densities. Photometric data for galaxies in the COSMOS field were used to constrain spectral energy distributions (SEDs) using the fitting tool CIGALE. These SEDs were used to create Gaussian prior estimates in the SPIRE bands for XID+. The multi-wavelength photometry and the extracted SPIRE flux densities were run through CIGALE again to allow us to compare the performance of the two priors. Inferred ALMA flux densities (F$^i$), at 870$\mu$m and 1250$\mu$m, from the best fitting SEDs from the second CIGALE run were compared with measured ALMA flux densities (F$^m$) as an independent performance validation. Similar validations were conducted with the SED modelling and fitting tool MAGPHYS and modified black body functions to test for model dependency. We demonstrate a clear improvement in agreement between the flux densities extracted with XID+ and existing data at other wavelengths when using the new informed Gaussian prior over the original uninformed prior. The residuals between F$^m$ and F$^i$ were calculated. For the Gaussian prior, these residuals, expressed as a multiple of the ALMA error ($\sigma$), have a smaller standard deviation, 7.95$\sigma$ for the Gaussian prior compared to 12.21$\sigma$ for the flat prior, reduced mean, 1.83$\sigma$ compared to 3.44$\sigma$, and have reduced skew to positive values, 7.97 compared to 11.50. These results were determined to not be significantly model dependent. This results in statistically more reliable SPIRE flux densities.
TL;DR: In this paper, the authors investigated the large-scale distribution of water in the G327.6 massive star-forming region and investigated possible variations of the water abundance as a function of evolution.
Abstract: Aims: Following our past study of the distribution of warm gas in the G327.3-0.6 massive star-forming region, we aim here at characterizing the large-scale distribution of water in this active region of massive star formation made of individual objects in different evolutionary phases. We investigate possible variations of the water abundance as a function of evolution. Methods: We present Herschel/PACS (4'× 4') continuum maps at 89 and179 μm encompassing the whole region (Hii region and the infrared dark cloud, IRDC) and an APEX/SABOCA (2'× 2') map at 350 μm of the IRDC. New spectral Herschel/HIFI maps toward the IRDC region covering the low-energy water lines at 987 and 1113 GHz (and their H218O counterparts) are also presented and combined with HIFI pointed observations toward the G327 hot core region. We infer the physical properties of the gas through optical depth analysis and radiative transfer modeling of the HIFI lines. Results: The distribution of the continuum emission at 89 and 179 μm follows the thermal continuum emission observed at longer wavelengths, with a peak at the position of the hot core and a secondary peak in the Hii region, and an arch-like layer of hot gas west of this Hii region. The same morphology is observed in the p-H2O 111-000 line, in absorption toward all submillimeter dust condensations. Optical depths of approximately 80 and 15 are estimated and correspond to column densities of 1015 and 2 × 1014 cm-2, respectively, for the hot core and IRDC position. These values indicate an abundance of water relative to H2 of 3 × 10-8 toward the hot core, while the abundance of water does not change along the IRDC with values close to some 10-8. Infall (over at least 20″) is detected toward the hot core position with a rate of 1-1.3 × 10-2M⊙ /yr, high enough to overcome the radiation pressure that is due to the stellar luminosity. The source structure of the hot core region appears 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 rather centered away from the hot core. Conclusions: The distribution of water along the IRDC is roughly constant with an abundance peak in the more evolved object, that is, in the hot core. These water abundances are in agreement with previous studies in other massive objects and chemical models. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
INAF1, Spanish National Research Council2, California Institute of Technology3, Ghent University4, Open University5, University of Maryland, College Park6, Centre national de la recherche scientifique7, Paris Diderot University8, Imperial College London9, University of La Laguna10, University of Tokyo11, European University Cyprus12, University of Arizona13, United States Naval Research Laboratory14, University of Padua15, University of Toulouse16, University of Alcalá17, Institut d'Astrophysique de Paris18, European Southern Observatory19, Nagoya University20, Tokyo Institute of Technology21, Japan Aerospace Exploration Agency22, University of California, Los Angeles23, Cardiff University24, Osaka University25, Ehime University26, University of Cambridge27, University of Bologna28, University of Geneva29, Sapienza University of Rome30, University of British Columbia31, University of Toledo32, Max Planck Society33, Royal Institute of Technology34
TL;DR: The SPACE IR telescope for Cosmology and Astrophysics (SPICA) as discussed by the authors was used to study the formation and evolution of galaxies and black holes through cosmic time, bridging the gap between the JWST and the new generation of Extremely Large Telescopes (ELTs) at shorter wavelengths and the Atacama Large Millimeter Array (ALMA) at longer wavelengths.
Abstract: 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.
TL;DR: In this paper, the influence of the outflow on the degree of deuteration of NGC 1333 IRAS 4A was investigated, in order to constrain the age of the object and compare it with a typical high-mass protostellar envelope.
Abstract: It is not well known what drives the chemistry of a protostellar envelope, in particular the role of the stellar mass and the outflows on its chemical enrichment. We study the chemical structure of NGC 1333 IRAS 4A in order to (i) investigate the influence of the outflows on the chemistry, (ii) constrain the age of our object, (iii) compare it with a typical high-mass protostellar envelope. In our analysis we use JCMT line mapping and HIFI pointed spectra. To study the influence of the outflow on the degree of deuteration, we compare JCMT maps of HCO+ and DCO+ with non-LTE (RADEX) models in a region that spatially covers the outflow activity of IRAS 4A. To study the envelope chemistry, we derive empirical molecular abundance profiles for the observed species using the radiative transfer code (RATRAN) and adopting a 1D dust density/temperature profile from the literature. We compare our best-fit observed abundance profiles with the predictions from the time dependent gas grain chemical code (ALCHEMIC). The CO, HCN, HNC and CN abundance require an enhanced UV field which points towards an outflow cavity. The abundances (wrt H2) are 1 to 2 orders of magnitude lower than those observed in the high mass protostellar envelope (AFGL 2591), while they are found to be similar within factors of a few with respect to CO. Differences in UV radiation may be responsible for such chemical differentiation, but temperature differences seem a more plausible explanation. The CH3OH modeled abundance profile points towards an age of > 4x10^4 yrs for IRAS 4A. The spatial distribution of H2D+ differs from that of other deuterated species, indicating an origin from a foreground colder layer (<20 K). The observed abundances can be explained by passive heating towards the high mass protostellar envelope, while the presence of UV cavity channels become more important toward the low mass protostellar envelope.
TL;DR: In this paper, a large-scale distribution of H2O in G327.6, a massive star-forming region made of individual objects in different evolutionary phases, is investigated.
Abstract: 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 $\mu$m of the whole region and an APEX map at 350 {\mu}m 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 {\mu}m 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.
INAF1, Paris Diderot University2, European Southern Observatory3, University of Padua4, California Institute of Technology5, Ghent University6, Imperial College London7, European University Cyprus8, Spanish National Research Council9, University of La Laguna10, University of Arizona11, University of Alcalá12, Cardiff University13, Nagoya University14, University of the Western Cape15, Open University16, University of Trieste17, University of Tokyo18, Japan Aerospace Exploration Agency19, Rutherford Appleton Laboratory20, Complutense University of Madrid21, University of British Columbia22, Netherlands Institute for Space Research23
TL;DR: In this paper, the authors 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.
Abstract: 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
Nagoya University1, Japan Aerospace Exploration Agency2, California Institute of Technology3, Ghent University4, Polish Academy of Sciences5, European University Cyprus6, INAF7, Spanish National Research Council8, University of La Laguna9, Institute for the Physics and Mathematics of the Universe10, University of Alcalá11, Cardiff University12, Graduate University for Advanced Studies13, Subaru14, University of Tokyo15, University of Bologna16, University of British Columbia17, University of Toledo18, University of the Western Cape19
TL;DR: In this article, the authors evaluate the capability of low-resolution mid-IR spectroscopic surveys of galaxies that could be performed by SPICA and demonstrate that the SPICA midIR surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-IR with SPICA.
Abstract: 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.