arXiv subjects

T. Nakagawa

Publications and source records attributed to T. Nakagawa.

At least 19 recordsLinked to original sources

arXiv2025

The Structure of the Relativistic Fe Line in GX 340+0 as Viewed with XRISM/Resolve, NICER, and NuSTAR

We present a 152 ks XRISM/Resolve observation of the persistently accreting Z source GX 340+0. Simultaneous observations also occurred with NuSTAR and NICER for 22.47 ks and 2.7 ks, respectively. The source covered the normal branch to the flaring branching during the observations. The data from all three missions were modeled concurrently for each spectral branch. The superior energy resolution of XRISM/Resolve reveals structure within the iron emission line complex regardless of spectral state. We model the reprocessed Fe K line with a reflection model tailored for thermal illumination of the accretion disk by a neutron star. The currently available model encompasses the broad components, but narrow emission features remain at the ~5% level. These remaining features may be described by the presence of an ionized plasma in the system as has been observed in the Z source Cygnus X-2, but subsequent updates to the reflection model code may be able to explain these features.

astro-ph.HE↗

arXiv2024

A GMRT 610 MHz radio survey of the North Ecliptic Pole (NEP, ADF-N) / Euclid Deep Field North

This paper presents a 610 MHz radio survey covering 1.94 square degrees around the North Ecliptic Pole (NEP), which includes parts of the AKARI (ADF-N) and Euclid, Deep Fields North. The median 5-sigma sensitivity is 28 microJy beam per beam, reaching as low as 19 microJy per beam, with a synthesised beam of 3.6 x 4.1 arcsec. The catalogue contains 1675 radio components, with 339 grouped into multi-component sources and 284 isolated components likely part of double radio sources. Imaging, cataloguing, and source identification are presented, along with preliminary scientific results. From a non-statistical sub-set of 169 objects with multi-wavelength AKARI and other detections, luminous infrared galaxies (LIRGs) represent 66 percent of the sample, ultra-luminous infrared galaxies (ULIRGs) 4 percent, and sources with L_IR < 1011 L_sun 30 percent. In total, 56 percent of sources show some AGN presence, though only seven are AGN-dominated. ULIRGs require three times higher AGN contribution to produce high-quality SED fits compared to lower luminosity galaxies, and AGN presence increases with AGN fraction. The PAH mass fraction is insignificant, although ULIRGs have about half the PAH strength of lower IR-luminosity galaxies. Higher luminosity galaxies show gas and stellar masses an order of magnitude larger, suggesting higher star formation rates. For LIRGs, AGN presence increases with redshift, indicating that part of the total luminosity could be contributed by AGN activity rather than star formation. Simple cross-matching revealed 13 ROSAT QSOs, 45 X-ray sources, and 61 sub-mm galaxies coincident with GMRT radio sources.

astro-ph.GA↗

arXiv2024

Effects of galaxy environment on merger fraction

Aims. In this work, we intend to examine how environment influences the merger fraction, from the low density field environment to higher density groups and clusters. We also aim to study how the properties of a group or cluster, as well as the position of a galaxy in the group or cluster, influences the merger fraction. Methods. We identified galaxy groups and clusters in the North Ecliptic Pole using a friends-of-friends algorithm and the local density. Once identified, we determined the central galaxies, group radii, velocity dispersions, and group masses of these groups and clusters. Merging systems were identified with a neural network as well as visually. With these, we examined how the merger fraction changes as the local density changes for all galaxies as well as how the merger fraction changes as the properties of the groups or clusters change. Results. We find that the merger fraction increases as local density increases and decreases as the velocity dispersion increases, as is often found in literature. A decrease in merger fraction as the group mass increases is also found. We also find groups with larger radii have higher merger fractions. The number of galaxies in a group does not influence the merger fraction. Conclusions. The decrease in merger fraction as group mass increases is a result of the link between group mass and velocity dispersion. Hence, this decrease of merger fraction with increasing mass is a result of the decrease of merger fraction with velocity dispersion. The increasing relation between group radii and merger fraction may be a result of larger groups having smaller velocity dispersion at a larger distance from the centre or larger groups hosting smaller, infalling groups with more mergers. However, we do not find evidence of smaller groups having higher merger fractions.

astro-ph.GA↗

arXiv2021

Electron g-factor determined for quantum dot circuit fabricated from (110)-oriented GaAs quantum well

The choice of substrate orientation for semiconductor quantum dot circuits offers opportunities for tailoring spintronic properties such as g-factors for specific functionality. In this letter, we demonstrate the operation of a few-electron double quantum dot circuit fabricated from a (110)-oriented GaAs quantum well. We estimate the in-plane electron g-factor from the profile of the enhanced inter-dot tunneling (leakage) current near zero magnetic field. Spin-blockade due to Pauli exclusion can block inter-dot tunneling. However, this blockade becomes inactive due to hyperfine interaction mediated spin flip-flop processes between electron spin states and the nuclear spin of the host material. The g-factor of absolute value ~0.1 found for a magnetic field parallel to the direction [11(bar)0], is approximately a factor of four lower than that for comparable circuits fabricated from material grown on widely-employed standard (001) GaAs substrates, and is in line with reported values determined by purely optical means for quantum well structures grown on (110) GaAs substrates.

cond-mat.mes-hall↗

arXiv2021

The formation of planetary systems with SPICA

In this era of spatially resolved observations of planet forming disks with ALMA and large ground-based telescopes such as the VLT, Keck and Subaru, we still lack statistically relevant information on the quantity and composition of the material that is building the planets, such as the total disk gas mass, the ice content of dust, and the state of water in planetesimals. SPICA is an infrared space mission concept developed jointly by JAXA and ESA to address these questions. The key unique capabilities of SPICA that enable this research are (1) the wide spectral coverage 10-220 micron, (2) the high line detection sensitivity of (1-2) 10-19 W m-2 with R~2000-5000 in the far-IR (SAFARI) and 10-20 W m-2 with R~29000 in the mid-IR (SMI, spectrally resolving line profiles), (3) the high far-IR continuum sensitivity of 0.45 mJy (SAFARI), and (4) the observing efficiency for point source surveys. This paper details how mid- to far-IR infrared spectra will be unique in measuring the gas masses and water/ice content of disks and how these quantities evolve during the planet forming period. These observations will clarify the crucial transition when disks exhaust their primordial gas and further planet formation requires secondary gas produced from planetesimals. The high spectral resolution mid-IR is also unique for determining the location of the snowline dividing the rocky and icy mass reservoirs within the disk and how the divide evolves during the build-up of planetary systems. Infrared spectroscopy (mid- to far-IR) of key solid state bands is crucial for assessing whether extensive radial mixing, which is part of our Solar System history, is a general process occurring in most planetary systems and whether extrasolar planetesimals are similar to our Solar System comets/asteroids. ... (abbreviated)

astro-ph.EP↗

arXiv2021

[CII] emission properties of the massive star-forming region RCW36 in a filamentary molecular cloud

Aims: To investigate properties of [CII]158 $μ$m emission of RCW36 in a dense filamentary cloud. Methods: [CII] observations of RCW36 covering an area of ~30 arcmin$\times$30 arcmin were carried out with a Fabry-Pérot spectrometer aboard a 100-cm balloon-borne far-infrared (IR) telescope with an angular resolution of 90 arcsec. By using AKARI and Herschel images, the spatial distribution of the [CII] intensity was compared with those of emission from the large grains and PAH. Results: The [CII] emission is spatially in good agreement with shell-like structures of a bipolar lobe observed in IR images, which extend along the direction perpendicular to the direction of a cold dense filament. We found that the [CII]--160 $μ$m relation for RCW36 shows higher brightness ratio of [CII]/160 $μ$m than that for RCW 38, while the [CII]--9 $μ$m relation for RCW36 is in good agreement with that for RCW38. Conclusions: The [CII] emission spatially well correlates with PAH and cold dust emissions. This means that the observed [CII] emission dominantly comes from PDRs. Moreover, the L_[CII]/L_FIR ratio shows large variation compared with the L_[CII]/L_PAH ratio. In view of the observed tight correlation between L_[CII]/L_FIR and the optical depth at $λ$=160 $μ$m, the large variation in L_[CII]/L_FIR can be simply explained by the geometrical effect, viz., L_FIR has contributions from the entire dust-cloud column along the line of sight, while L_[CII] has contributions from far-UV illuminated cloud surfaces. Based on the picture of the geometry effect, the enhanced brightness ratio of [CII]/160 $μ$m is attributed to the difference in gas structures where massive stars are formed: filamentary (RCW36) and clumpy (RCW38) molecular clouds and thus suggests that RCW36 is dominated by far-UV illuminated cloud surfaces compared with RCW38.

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

Probing the High-Redshift Universe with SPICA: Toward the Epoch of Reionization and Beyond

With the recent discovery of a dozen dusty star-forming galaxies and around 30 quasars at z>5 that are hyper-luminous in the infrared ($μ$$L_{\rm IR}>10^{13}$ L$_{\odot}$, where $μ$ is a lensing magnification factor), the possibility has opened up for SPICA, the proposed ESA M5 mid-/far-infrared mission, to extend its spectroscopic studies toward the epoch of reionization and beyond. In this paper, we examine the feasibility and scientific potential of such observations with SPICA's far-infrared spectrometer SAFARI, which will probe a spectral range (35-230 $μ$m) that will be unexplored by ALMA and JWST. Our simulations show that SAFARI is capable of delivering good-quality spectra for hyper-luminous infrared galaxies (HyLIRGs) at z=5-10, allowing us to sample spectral features in the rest-frame mid-infrared and to investigate a host of key scientific issues, such as the relative importance of star formation versus AGN, the hardness of the radiation field, the level of chemical enrichment, and the properties of the molecular gas. From a broader perspective, SAFARI offers the potential to open up a new frontier in the study of the early Universe, providing access to uniquely powerful spectral features for probing first-generation objects, such as the key cooling lines of low-metallicity or metal-free forming galaxies (fine-structure and H2 lines) and emission features of solid compounds freshly synthesized by Population III supernovae. Ultimately, SAFARI's ability to explore the high-redshift Universe will be determined by the availability of sufficiently bright targets (whether intrinsically luminous or gravitationally lensed). With its launch expected around 2030, SPICA is ideally positioned to take full advantage of upcoming wide-field surveys such as LSST, SKA, Euclid, and WFIRST, which are likely to provide extraordinary targets for SAFARI.

astro-ph.GA↗

arXiv2018

Orbital characterization of GJ1108A system, and comparison of dynamical mass with model-derived mass for resolved binaries

We report an orbital characterization of GJ1108Aab that is a low-mass binary system in pre-main-sequence phase. Via the combination of astrometry using adaptive optics and radial velocity measurements, an eccentric orbital solution of $e$=0.63 is obtained, which might be induced by the Kozai-Lidov mechanism with a widely separated GJ1108B system. Combined with several observed properties, we confirm the system is indeed young. Columba is the most probable moving group, to which the GJ1108A system belongs, although its membership to the group has not been established. If the age of Columba is assumed for GJ1108A, the dynamical masses of both GJ1108Aa and GJ1108Ab ($M_{\rm dynamical,GJ1108Aa}=0.72\pm0.04 M_{\odot}$ and $M_{\rm dynamical,GJ1108Ab}=0.30\pm0.03 M_{\odot}$) are more massive than what an evolutionary model predicts based on the age and luminosities. We consider the discrepancy in mass comparison can attribute to an age uncertainty; the system is likely older than stars in Columba, and effects that are not implemented in classical models such as accretion history and magnetic activity are not preferred to explain the mass discrepancy. We also discuss the performance of the evolutionary model by compiling similar low-mass objects in evolutionary state based on the literature. Consequently, it is suggested that the current model on average reproduces the mass of resolved low-mass binaries without any significant offsets.

astro-ph.SR↗

arXiv2018

AKARI mid-infrared slitless spectroscopic survey of star-forming galaxies at $z\lesssim 0.5$

Deep MIR surveys have revealed numerous strongly star-forming galaxies at redshift z~<2. Their MIR fluxes are produced by a combination of continuum and PAH emission features. The PAH features can dominate the total MIR flux, but are difficult to measure without spectroscopy. We aim to study star-forming galaxies by using a blind spectroscopic survey at MIR wavelengths to understand evolution of their star formation rate (SFR) and specific SFR up to z~=0.5, by paying particular attention to their PAH properties. We conducted a low-resolution (R~=50) slitless spectroscopic survey at 5-13um of 9um flux-selected sources (>0.3 mJy) around the North Ecliptic Pole with the Infrared Camera (IRC) onboard AKARI. After removing 11 AGN candidates by using the IRC photometry, we identified 48 PAH galaxies with PAH 6.2, 7.7, and 8.6um features at z<0.5. The rest-frame optical-MIR spectral energy distributions (SEDs) based on CFHT and AKARI/IRC imaging covering 0.37-18um were produced, and analysed in conjunction with the PAH spectroscopy. We defined the PAH enhancement by using the luminosity ratio of the 7.7um PAH feature over the 3.5um stellar component of the SEDs. The rest-frame SEDs of all PAH galaxies have a universal shape with stellar and 7.7um bumps, except that the PAH enhancement significantly varies as a function of the PAH luminosities. We identified a PAH-enhanced population at z~>0.35, whose SEDs and luminosities are typical of luminous infrared galaxies. They show particularly larger PAH enhancement at high luminosity, implying that they are vigorous star-forming galaxies with elevated specific SFR. Our composite starburst model that combines a very young and optically very thick starburst with a very old population can successfully reproduce most of their SED characteristics, although we could not confirm this optically thick component from our spectral analysis.

astro-ph.GA↗

arXiv2018

MIRIS observation of near-infrared diffuse Galactic light

We report near-infrared (IR) observations of high Galactic latitude clouds to investigate diffuse Galactic light (DGL), which is starlight scattered by interstellar dust grains. The observations were performed at $1.1$ and $1.6\,\rm{μm}$ with a wide-field camera instrument, the Multi-purpose Infra-Red Imaging System (MIRIS) onboard the Korean satellite STSAT-3. The DGL brightness is measured by correlating the near-IR images with a far-IR $100\,\rm{μm}$ map of interstellar dust thermal emission. The wide-field observation of DGL provides the most accurate DGL measurement achieved to date. We also find a linear correlation between optical and near-IR DGL in the MBM32 field. To study interstellar dust properties in MBM32, we adopt recent dust models with or without $\rm{μm}$-sized very large grains and predict the DGL spectra, taking into account reddening effect of interstellar radiation field. The result shows that observed color of the near-IR DGL is closer to the model spectra without very large grains. This may imply that dust growth in the observed MBM32 field is not active owing to its low density of interstellar medium.

astro-ph.GA↗

arXiv2018

SPICA - a large cryogenic infrared space telescope Unveiling the obscured Universe

Measurements in the infrared wavelength domain allow us to assess directly the physical state and energy balance of cool matter in space, thus enabling the detailed study of the various processes that govern the formation and early evolution of stars and planetary systems in galaxies over cosmic time. Previous infrared missions, from IRAS to Herschel, have revealed a great deal about the obscured Universe, but sensitivity has been limited because up to now it has not been possible to fly a telescope that is both large and cold. SPICA is a mission concept aimed at taking the next step in mid- and far-infrared observational capability by combining a large and cold telescope with instruments employing state-of-the-art ultra-sensitive detectors. The mission concept foresees a 2.5-meter diameter telescope cooled to below 8 K. With cooling provided by mechanical coolers instead of depending on a limited cryogen supply, the mission lifetime can extend significantly beyond the required three years. SPICA offers instrumentation with spectral resolving powers ranging from R ~50 through 11000 in the 17-230 $μ$m domain as well as R~28.000 spectroscopy between 12 and 18 $μ$m. Additionally SPICA will provide efficient 30-37 $μ$m broad band mapping, and polarimetric imaging in the 100-350 $μ$m range. SPICA will provide unprecedented spectroscopic sensitivity of ~5 x $10^{-20}$ W/m$^2$ (5$σ$/1hr) - at least two orders of magnitude improvement over what has been attained to date. With this exceptional leap in performance, new domains in infrared astronomy will become accessible, allowing us, for example, to unravel definitively galaxy evolution and metal production over cosmic time, to study dust formation and evolution from very early epochs onwards, and to trace the formation history of planetary systems.

astro-ph.IM↗

arXiv2017

The Near-Infrared CO Absorption Band as a Probe to the Innermost Part of an AGN Obscuring Material

We performed a systematic analysis of the 4.67 $μ$m CO ro-vibrational absorption band toward nearby active galactic nuclei (AGNs) and analyzed the absorption profiles of ten nearby galaxies collected from the AKARI and Spitzer spectroscopic observations that show the CO absorption feature by fitting a plane-parallel local thermal equilibrium gas model. We found that CO gas is warm (200--500 K) and has a large column density ($N_\mathrm{H}\gtrsim10^{23}~\mathrm{cm^{-2}}$). The heating of the gas is not explicable by either UV heating or shock heating because these processes cannot represent the large column densities of the warm gas. Instead, X-ray photons from the nuclei, which can produce large columns of warm gas with up to $N_\mathrm{H}\sim10^{24}~\mathrm{cm^{-2}}$, are the most convincing power source. The hydrogen column density estimated from the CO band is smaller than that inferred from X-ray observations. These results indicate that the region probed by the near-infrared CO absorption is in the vicinity of the nuclei and is located outside the X-ray emitting region. Furthermore, the covering factors close to unity required by the observed deep absorption profiles suggest that the probed region is close to the continuum source, which can be designated as the inner rim of the obscuring material around the AGN.

astro-ph.GA↗

arXiv2017

Probing the baryon cycle of galaxies with SPICA mid- and far-infrared observations

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 $μ$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 $μ$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.

astro-ph.GA↗

arXiv2017

Overview of North Ecliptic Pole Deep multi-wavelength Survey (NEP-Deep)

The recent updates of the North Ecliptic Pole deep (0.5~deg$^2$, NEP-Deep) multi-wavelength survey covering from X-ray to radio-wave is presented. The NEP-Deep provides us with several thousands of 15~$μ$m or 18~$μ$m selected sample of galaxies, which is the largest sample ever made at this wavelengths. A continuous filter coverage in the mid-infrared wavelength (7, 9, 11, 15, 18, and 24~$μ$m) is unique and vital to diagnose the contributions from starbursts and AGNs in the galaxies out to $z$=2.The new goal of the project is to resolve the nature of the cosmic star formation history at the violent epoch (e.g. $z$=1--2), and to find a clue to understand its decline from $z$=1 to present universe by utilizing the unique power of the multi-wavelength survey. The progress in this context is briefly mentioned.

astro-ph.GA↗

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↗