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<i>Spitzer Planck Herschel</i> Infrared Cluster (SPHerIC) survey: Candidate galaxy clusters at 1.3 < <i>z</i> < 3 selected by high star-formation rate
摘要： There is a lack of large samples of spectroscopically confirmed clusters and protoclusters at high redshifts, z > 1.5. Discovering and characterizing distant (proto-)clusters is important for yielding insights into the formation of large-scale structure and on the physical processes responsible for regulating star-formation in galaxies in dense environments. The Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey was initiated to identify these characteristically faint and dust-reddened sources during the epoch of their early assembly. We present Spitzer/IRAC observations of 82 galaxy (proto-)cluster candidates at 1.3 < zp < 3.0 that were vetted in a two step process: (1) using Planck to select by color those sources with the highest star-formation rates, and (2) using Herschel at higher resolution to separate out the individual red sources. The addition of the Spitzer data enables efficient detection of the central and massive brightest red cluster galaxies (BRCGs). We find that BRCGs are associated with highly significant, extended and crowded regions of IRAC sources which are more overdense than the field. This result corroborates our hypothesis that BRCGs within the Planck–Herschel sources trace some of the densest and actively star-forming proto-clusters in the early Universe. On the basis of a richness-mass proxy relation, we obtain an estimate of their mean masses which suggests our sample consists of some of the most massive clusters at z ≈ 2 and are the likely progenitors of the most massive clusters observed today.
关键词： galaxies: star formation,submillimeter: galaxies,infrared: galaxies,galaxies: evolution,galaxies: clusters: general,galaxies: high-redshift
更新于2025-09-23 15:23:52
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The near-to-mid infrared spectrum of quasars
摘要： We analyse a sample of 85 luminous (log (νLν(3 μm)/erg s?1) > 45.5) quasars with rest frame ～2–11 μm spectroscopy from AKARI and Spitzer. Their high luminosity allows a direct determination of the near-infrared quasar spectrum free from host galaxy emission. A semi-empirical model consisting of a single template for the accretion disc and two blackbodies for the dust emission successfully reproduces the 0.1–10 μm spectral energy distributions (SEDs). Excess emission at 1–2 μm over the best-fitting model suggests that hotter dust is necessary in addition to the ～1200 K blackbody and the disc to reproduce the entire near-infrared spectrum. Variation in the extinction affecting the disc and in the relative strength of the disc and dust components accounts for the diversity of individual SEDs. Quasars with higher dust-to-disc luminosity ratios show slightly redder infrared continua and less prominent silicate emission. We find no luminosity dependence in the shape of the average infrared quasar spectrum. We generate a new quasar template that covers the rest-frame range 0.1–11 μm, and separate templates for the disc and dust components. Comparison with other infrared quasar composites suggests that previous ones are less reliable in the 2–4 μm range. Our template is the first one to provide a detailed view of the infrared emission on both sides of the 4 μm bump.
关键词： infrared: galaxies,galaxies: active,quasars: emission lines,quasars: general
更新于2025-09-23 15:23:52
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ALMA-backed NIR high resolution integral field spectroscopy of the NUGA galaxy NGC 1433
摘要： Aims. We present the results of near-infrared (NIR) H- and K-band European Southern Observatory SINFONI integral field spectroscopy (IFS) of the Seyfert 2 galaxy NGC 1433. We investigate the central 500 pc of this nearby galaxy, concentrating on excitation conditions, morphology, and stellar content. NGC 1433 was selected from our extended NUGA(-south) sample, which was additionally observed with the Atacama Large Millimeter/submillimeter Array (ALMA). NGC 1433 is a ringed, spiral galaxy with a main stellar bar in roughly east–west direction (PA 94?) and a secondary bar in the nuclear region (PA 31?). Several dusty filaments are detected in the nuclear region with the Hubble Space Telescope. ALMA detects molecular CO emission coinciding with these filaments. The active galactic nucleus is not strong and the galaxy is also classified as a low-ionization emission-line region (LINER). Methods. The NIR is less affected by dust extinction than optical light and is sensitive to the mass-dominating stellar populations. SINFONI integral field spectroscopy combines NIR imaging and spectroscopy, allowing us to analyse several emission and absorption lines to investigate the stellar populations and ionization mechanisms over the 10'' × 10'' field of view (FOV). Results. We present emission and absorption line measurements in the central kpc of NGC 1433. We detect a narrow Balmer line and several H2 lines. We find that the stellar continuum peaks in the optical and NIR in the same position, indicating that there is no covering of the center by a nuclear dust lane. A strong velocity gradient is detected in all emission lines at that position. The position angle of this gradient is at 155? whereas the galactic rotation is at a position angle of 201?. Our measures of the molecular hydrogen lines, hydrogen recombination lines, and [Fe II] indicate that the excitation at the nucleus is caused by thermal excitation, i.e., shocks that can be associated with active galactic nuclei emission, supernovae, or outflows. The line ratios [Fe II]/Paβ and H2/Brγ show a Seyfert to LINER identification of the nucleus. We do not detect high star formation rates in our FOV. The stellar continuum is dominated by spectral signatures of red-giant M stars. The stellar line-of-sight velocity follows the galactic field whereas the light continuum follows the nuclear bar. Conclusions. The dynamical center of NGC 1433 coincides with the optical and NIR center of the galaxy and the black hole position. Within the central arcsecond, the molecular hydrogen and the 12CO(3?2) emissions – observed in the NIR and in the submillimeter with SINFONI and ALMA, respectively – are indicative for a nuclear outflow originating from the galaxy’s SMBH. A small circumnuclear disk cannot be fully excluded. Derived gravitational torques show that the nuclear bar is able to drive gas inward to scales where viscosity torques and dynamical friction become important. The black hole mass, derived using stellar velocity dispersion, is ～107 M☉.
关键词： galaxies: nuclei,galaxies: individual: NGC 1433,galaxies: active,infrared: galaxies,galaxies: ISM,galaxies: kinematics and dynamics
更新于2025-09-23 15:22:29
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Characteristics of mid-infrared PAH emission from star-forming galaxies selected at 250?μm in the North Ecliptic Pole field
摘要： Evolutionary properties of infrared (IR) luminous galaxies are important keys to understand dust-obscured star formation history and galaxy evolution. Based on near- to mid-IR imaging with nine continuous filters of the AKARI space telescope, we present the characteristics of dusty star-forming (SF) galaxies showing polycyclic aromatic hydrocarbon (PAH) features observed by the North Ecliptic Pole (NEP) wide field survey of AKARI and Herschel. All the sample galaxies from the AKARI/NEP-Wide data are selected based both on the Herschel/SPIRE 250 μm detection and optical spectroscopic redshift data. The physical modeling of spectral energy distribution (SED) using all available data points from u* to sub-mm 500 μm band, including WISE and PACS data where available, takes unique advantages of the continuous near- to mid-IR coverage, the reliable constraint on the far-IR peak, and spectroscopically determined accurate redshifts, as well as the energy balance principle by MAGPHYS. This enables us to derive physically meaningful and accurate total infrared luminosity and 8 μm (or PAH) luminosity consistently. Our sample galaxies are in the redshift range z < 1, and the majority of them appear to be normal SF/spiral populations showing PAH features near 8 μm. These SF galaxies showing PAHs in the mid-IR include various types, from quiescent to starbursts. Some of our sample show shortage of 8 μm luminosity compared to the total IR luminosity and this PAH deficit gets severe in more-luminous IR galaxies, suggesting PAH molecules in these galaxies are destroyed by a strong radiation field from the SF region or a large amount of cold dust in the interstellar medium. The specific SFR of our sample shows mass-dependent time evolution which is consistent with a downsizing evolutionary pattern.
关键词： cosmology: observations,galaxies: evolution,infrared: galaxies
更新于2025-09-23 15:22:29
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<i>Spitzer</i> Matching Survey of the UltraVISTA Ultra-deep Stripes (SMUVS): Full-mission IRAC Mosaics and Catalogs
摘要： This paper describes new deep 3.6 and 4.5 μm imaging of three UltraVISTA near-infrared survey stripes within the COSMOS field. The observations were carried out with Spitzer's Infrared Array Camera (IRAC) for the Spitzer Matching Survey of the UltraVISTA Deep Stripes (SMUVS). In this work we present our data reduction techniques, and document the resulting mosaics, coverage maps, and catalogs in both IRAC passbands for the three easternmost UltraVISTA survey stripes, covering a combined area of about 0.66 deg2, of which 0.45 deg2 have at least 20 hr of integration time. SMUVS reaches point-source sensitivities of about 25.0 AB mag (0.13 μJy) at both 3.6 and 4.5 μm, with a significance of 4σ, accounting for both survey sensitivity and source confusion. To this limit the SMUVS catalogs contain a total of ～350,000 sources, each of which is detected significantly in at least one IRAC band. Because of its uniform and high sensitivity, relatively large area coverage, and the wide array of ancillary data available in COSMOS, the SMUVS survey will be useful for a large number of cosmological investigations. We make all images and catalogs described herein publicly available via the Spitzer Science Center.
关键词： surveys,infrared: galaxies,catalogs
更新于2025-09-23 15:22:29
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The power of infrared AGN selection in mergers: a theoretical study
摘要： The role of galaxy mergers in fuelling active galactic nuclei (AGNs) is still debated, owing partly to selection effects inherent to studies of the merger/AGN connection. In particular, luminous AGNs are often obscured in late-stage mergers. Mid-infrared (IR) colour selection of dust-enshrouded AGN with, e.g. the Wide-field Infrared Survey Explorer (WISE) has uncovered large new populations of obscured AGN. However, this method is sensitive mainly to AGN that dominate emission from the host. To understand how selection biases affect mid-IR studies of the merger/AGN connection, we simulate the evolution of AGN throughout galaxy mergers. Although mid-IR colours closely trace luminous, obscured AGN, we show that nearly half of merger-triggered AGNs are missed with common mid-IR selection criteria, even in late-stage, gas-rich major mergers. At z (cid:2) 0.5, where merger signatures and dual nuclei can most easily be detected, we find that a more lenient W1 ? W2 > 0.5 cut greatly improves completeness without significantly decreasing reliability. Extreme nuclear starbursts are briefly able to mimic this AGN signature, but this is largely irrelevant in mergers, where such starbursts are accompanied by AGN. We propose a two-colour cut that yields high completeness and reliability even in starbursting systems. Further, we show that mid-IR colour selection very effectively identifies dual AGN hosts, with the highest fraction at the smallest separations (<3 kpc). Thus, many merger hosts of mid-IR AGN should contain unresolved dual AGN; these are ideal targets for high-resolution follow-up, particularly with the James Webb Space Telescope.
关键词： galaxies: interactions,infrared: galaxies,accretion,accretion discs,galaxies: active,black hole physics
更新于2025-09-23 15:21:21
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Total infrared luminosity estimation from local galaxies in AKARI all sky survey
摘要： We aim to use the a new and improved version of AKARI all sky survey catalogue of far-infrared sources to recalibrate the formula to derive the total infrared luminosity. We cross-match the faint source catalogue (FSC) of IRAS with the new AKARI-FIS and obtained a sample of 2430 objects. Then we calculate the total infrared (TIR) luminosity LTIR from the formula previously estimated from IRAS data and compare it with total infrared luminosity from AKARI FIS bands to obtain new coe?cients for the general relation to convert FIR luminosity from AKARI bands to the TIR luminosity.
关键词： infrared: galaxies,galaxies: star formation,galaxies: evolution
更新于2025-09-23 15:21:21
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Near-infrared spectroscopic indices for unresolved stellar populations
摘要： Context. A new generation of spectral synthesis models has been developed in recent years, but there is no matching set of template galaxy spectra, in terms of quality and resolution, for testing and refining the new models. Aims. Our main goal is to find and calibrate new near-infrared spectral indices along the Hubble sequence of galaxies which will be used to obtain additional constraints to the population analysis based on medium-resolution integrated spectra of galaxies. Methods. Spectra of previously studied and well-understood galaxies with relatively simple stellar populations (e.g., ellipticals or bulge dominated galaxies) are needed to provide a baseline data set for spectral synthesis models. Results. X-shooter spectra spanning the optical and infrared wavelengths (350–2400 nm) of bright nearby elliptical galaxies with a resolving power of R ～ 4000–5400 were obtained. Heliocentric systemic velocity, velocity dispersion, and Mg, Fe, and Hβ line-strength indices are presented. Conclusions. We present a library of very-high-quality spectra of galaxies covering a large range of age, metallicity, and morphological type. Such a dataset of spectra will be crucial to addressing important questions of the modern investigation concerning galaxy formation and evolution.
关键词： galaxies: formation,galaxies: stellar content,infrared: galaxies,surveys,galaxies: abundances
更新于2025-09-23 15:19:57
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Near- to mid-infrared spectroscopy of the heavily obscured AGN LEDA 1712304 with AKARI/IRC
摘要： Context. Although heavily obscured active galactic nuclei (AGNs) have been found by many observational studies, the properties of the surrounding dust are poorly understood. Using AKARI/IRC spectroscopy, we discovered a new heavily obscured AGN in LEDA 1712304 which shows a deep spectral absorption feature due to silicate dust. Aims. We study the infrared (IR) spectral properties of circumnuclear silicate dust in LEDA 1712304. Methods. We performed IR spectral fitting, considering silicate dust properties such as composition, porosity, size, and crystallinity. Spectral energy distribution fitting was also performed on the flux densities in the UV to submillimeter range to investigate the global spectral properties. Results. The best-fit model indicates 0.1 μm-sized porous amorphous olivine (Mg2xFe2?2xSiO4; x = 0.4) with 4% crystalline pyroxene. The optical depth is τsil ～ 2.3, while the total IR luminosity and stellar mass are estimated to be LIR = (5 ± 1) × 1010 L(cid:12) and Mstar = (2.7 ± 0.8) × 109 M(cid:12), respectively. In such low LIR and Mstar ranges, there are few galaxies that show such a large τsil. Conclusion. The silicate dust in the AGN torus of LEDA 1712304 has properties that are notably similar to those in other AGNs overall, but slightly different in the wing shape of the absorption profile. The porosity of the silicate dust suggests dust coagulation or processing in the circumnuclear environments, while the crystallinity suggests that the silicate dust is relatively fresh.
关键词： galaxies: nuclei,galaxies: individual: LEDA 1712304,infrared: galaxies
更新于2025-09-12 10:27:22
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Enhancing the H <sub/>2</sub> O Megamaser Detection Rate Using Optical and Mid-infrared Photometry
摘要： Water megamasers from circumnuclear disks in galaxy centers provide the most accurate measurements of supermassive black hole masses and uniquely probe the subparsec accretion processes. At the same time, these systems offer independent crucial constraints of the Hubble constant in the nearby universe, and thus, the arguably best single constraint on the nature of dark energy. The chances of finding these golden standards are, however, abysmally low, at ～3% overall for any level of water maser emission detected at 22 GHz and ～1% for those exhibiting disk-like configuration. We provide here a thorough summary of the current state of detection of water megamaser disks along with a novel investigation of the likelihood of increasing their detection rates based on a multivariate parameter analysis of the optical and mid-infrared (mid-IR) photometric properties of the largest database of galaxies surveyed for 22 GHz emission. We find that galaxies with water megamaser emission tend to be associated with strong emission in all Wide-field Infrared Survey Explorer mid-IR wavelengths, with the strongest enhancement in the W4 band, at 22 μm, as well as with previously proposed and newly found indicators of active galactic nucleus strength in the mid-IR, such as red W1?W2 and W1?W4 colors, and the integrated mid-IR luminosity of the host galaxy. These trends offer a potential boost of the megamaser detection rates to 6%–15%, or a factor of 2–8 relative to the current rates, depending on the chosen sample selection criteria, while fostering real chances for discovering ～20 new megamaser disks.
关键词： infrared: galaxies,surveys,galaxies: nuclei,galaxies: active,masers
更新于2025-09-10 09:29:36