Investigating Clusters of Galaxies with Planck and Herschel

With the Planck and Herschel satellite missions of the European Space Agency, the far-infrared and submillimeter window will offer new investigation tools toward clusters of galaxies in the distant Universe. These are the Sunyaev Zel'dovich (SZ) effect of the cosmic microwave background and the thermal emission of dust grains. The power of the SZ effect is such that Planckis expected to discover thousands of new clusters at redshifts larger than 0.2, where only a few tens are known today. The dust can be present at large scale in the intracluster medium, and we show that even at very low abundances it is able to be a major cooling agent for the whole cluster. However the dominating dust emission will be that of the background infrared star forming galaxies. In all cases, the data processing of space borne sensitive submillimeter observations of clusters of galaxies such as the one that Planck and Herschel will provide, will require a very carefull combined analysis of the SZ effect and dust thermal emission.     

The Far‐Infrared Emission of Galaxies

C01 Study of local infrared bright galaxies with HERSHCEL‐PACS C02 PDR modeling of the COBE Far‐Infrared data of the Milky Way C03 MAMBO observations of BzK‐selected vigorous starburst galaxies at z ∼ 2 C04 Starburst galaxies in the far‐infrared. Modelling the line, PAH and dust continuum emission C05 The SED from isothermal clouds C06 PDRs in M83 and M51: The road to HIFI/Herschel and SOFIA C07 Large Scale Mapping of Molecular Gas in the Vicinity of 30 Doradus in the Large Magellanic Cloud C08 Modelling far‐infrared emission from dust in gas‐rich galaxies C09 [CII]/CO(1‐0) Line Ratio at low Metallicities C10 Gas, Stars and Dust in the Spiral Arms of M51 C11 The ISOPHOT 170 micron Serendipity Survey (ISOSS) catalog of optically identified galaxies C12 Spitzer Images of M33: A Probe to Radio‐FIR Correlation C13 Observations of far‐infrared emission from dust in gas‐rich galaxies C14 Dust and Gas in Nearby Galaxies: First Results from SINGS and THINGS C15 Sequential Starburst in Arp220?     

New Observing Opportunities in the Far‐Infrared and Submillimeter Range

F01 CONDOR – 1.4 THz Hetrodyne Receiver for APEX and for GREAT on SOFIA F02 FLASH – a First Light APEX Submillimeter Heterodyne instrument F03 GREAT – The German first light heterodyne instrument for SOFIA F04 CHAMP+ – A powerfull submillimeter array for the APEX telescope F05 The JamesWebb Space Telescope (JWST) and its Mid Infrared Instrument (MIRI) F06 CHARM – a Compact Heterodyne Array Receiver Module for KOSMA with Scalable Fully Reflective Focal Plane Array Optics F07 Science with Herschel‐PACS F08 CI/CO Mapping of IC 348 & Cepheus B using SMART on KOSMA F09 The warm and dense interstellar medium observed with Herschel F10 Intelligent Detectors – On‐Board Data Reduction for Future Missions F11 The Herschel Photodetector Array Camera & Spectrometer PACS F12 Why Astromineralogy Should Care about the Far‐infrared Range F13 ESI: A European Imaging Far‐Infrared Spectrometer for the Japanese SPICA space observatory F14 STAR – A 16 Pixel Terahertz Array Receiver for SOFIA F15 FIFI LS, a Field‐Imaging Far‐Infrared Line‐Spectrometer for SOFIA F16 Characterization of high‐ and low‐stressed Ge:Ga array cameras for Herschel's PACS instrument F17 Herschel / PACS Guaranteed Time Programs at MPIA F18 NANTEN2: CI and mid‐J CO surveys of clouds and galaxies of the southern sky     

The James Webb Space Telescope and its Infrared Detectors

The James Webb Space Telescope (JWST) was conceived as the scientific successor to the Hubble Space Telescope (HST) and Spitzer Space Telescope. The instrument suite provides broad wavelength coverage and capabilities aimed at four key science themes: 1) The end of the dark ages: first light and reionization, 2) The assembly of galaxies, 3) The birth of stars and protoplanetary systems, and 4) Planetary systems and the origins of life. To accomplish these ambitious goals, JWST's detectors provide state-of-the-art performance spanning the λ = 0.6–28 μm wavelength range. In this paper, we describe JWST with an emphasis on its infrared detectors.     

Confirming a population of hot-dust dominated, star-forming, ultraluminous galaxies at high redshift

We identify eight   z > 1  radio sources undetected at 850 μm but robustly detected at 70 μm, confirming that they represent ultraluminous infrared galaxies (ULIRGs) with hotter dust temperatures  (〈 T _d〉= 52 ± 10 K)  than submillimetre galaxies (SMGs) at similar luminosities and redshifts. These galaxies share many properties with SMGs: ultraviolet spectra consistent with starbursts, high stellar masses and radio luminosities. We can attribute their radio emission to star formation since high-resolution Multi-Element Radio Linked Interferometer Network (MERLIN) radio maps show extended emission regions (with characteristic radii of 2–3 kpc), which are unlikely to be generated by active galactic nucleus (AGN) activity. These observations provide the first direct confirmation of hot, dusty ULIRGs which are missed by current submillimetre surveys. They have significant implications for future observations from the Herschel Space Observatory and Submillimetre Common-User Bolometer Array 2 (SCUBA2), which will select high-redshift luminous galaxies with less selection biases.     

Variations in 24-μm morphologies among galaxies in the Spitzer Infrared Nearby Galaxies Survey: new insights into the Hubble sequence

To study the distribution of star formation and dust emission within nearby galaxies, we measured five morphological parameters in the 3.6- and 24-μm wavebands for 65 galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS) and eight galaxies that were serendipitously observed by SINGS. The morphological parameters demonstrate strong variations along the Hubble sequence, including statistically significant differences between S0/a-Sab and Sc-Sd galaxies. Early-type galaxies are generally found to be compact, centralized, symmetric sources in the 24-μm band, while late-type galaxies are generally found to be extended, asymmetric sources. These results suggest that the processes that increase the real or apparent sizes of galaxies' bulges also lead to more centralized 24-μm dust emission. Several phenomena, such as strong nuclear star formation, Seyfert activity, or outer ring structures, may cause galaxies to deviate from the general morphological trends observed at 24 μm. We also note that the 24-μm morphologies of Sdm-Im galaxies are quite varied, with some objects appearing very compact and symmetric but others appearing diffuse and asymmetric. These variations reflect the wide variation in star formation in irregular galaxies as observed at other wavelengths. The variations in the 24-μm morphological parameters across the Hubble sequence mirror many of the morphological trends seen in other tracers of the ISM and in stellar emission. However, the 24-μm morphological parameters for the galaxies in this sample do not match the morphological parameters measured in the stellar wavebands. This implies that the distribution of dust emission is related to but not equivalent to the distribution of stellar emission.     

The expected detection of dust emission from high-redshift Lyman α galaxies

Recent results have shown that a substantial fraction of high-redshift Lyman α (Lyα) galaxies contain considerable amounts of dust. This implies that Lyα galaxies are not primordial, as has been thought in the past. However, this dust has not been directly detected in emission; rather it has been inferred based on extinction estimates from rest-frame ultraviolet (UV) and optical observations. This can be tricky, as both dust and old stars redden galactic spectra at the wavelengths used to infer dust. Measuring dust emission directly from these galaxies is thus a more accurate way to estimate the total dust mass, giving us real physical information on the stellar populations and interstellar medium enrichment. New generation instruments, such as the Atacama Large Millimeter Array and Sub-Millimeter Array, should be able to detect dust emission from some of these galaxies in the submillimeter. Using measurements of the UV spectral slopes, we derive far-infrared flux predictions for of a sample of  23 z ≥ 4  Lyα galaxies. We find that in only a few hours, we can detect dust emission from 39 ± 22 per cent of our Lyα galaxies. Comparing these results to those found from a sample of 21 Lyman break galaxies (LBGs), we find that LBGs are on average 60 per cent more likely to be detected than Lyα galaxies, implying that they are more dusty, and thus indicating an evolutionary difference between these objects. These observations will provide better constraints on dust in these galaxies than those derived from their UV and optical fluxes alone. Undeniable proof of dust in these galaxies could explain the larger than expected Lyα equivalent widths seen in many Lyα galaxies today.     

The link between SCUBA and Spitzer: cold galaxies at z≲ 1

We show that the far-IR properties of distant Luminous and UltraLuminous InfraRed Galaxies (LIRGs and ULIRGs, respectively) are on average divergent from analogous sources in the local Universe. Our analysis is based on Spitzer Multiband Imaging Photometer (MIPS) and Infrared Array Camera (IRAC) data of   L _IR > 10¹⁰ L_⊙, 70 μm  selected objects in the  0.1 < z < 2  redshift range and supported by a comparison with the IRAS Bright Galaxy Sample. The majority of the objects in our sample are described by spectral energy distributions (SEDs) which peak at longer wavelengths than local sources of equivalent total infrared luminosity. This shift in SED peak wavelength implies a noticeable change in the dust and/or star-forming properties from   z ∼ 0  to the early Universe, tending towards lower dust temperatures, indicative of strong evolution in the cold dust, 'cirrus', component. We show that these objects are potentially the missing link between the well-studied local IR-luminous galaxies, Spitzer IR populations and SCUBA sources – the   z < 1  counterparts of the cold   z > 1  SubMillimetre Galaxies (SMGs) discovered in blank-field submillimetre surveys. The Herschel Space Observatory is well placed to fully characterize the nature of these objects, as its coverage extends over a major part of the far-IR/sub-mm SED for a wide redshift range.     

Infrared–red cores in nearby elliptical galaxies

We present the Spitzer Space Telescope Infrared Array Camera observations for a sample of local elliptical galaxies to study later stages of active galactic nucleus (AGN) activity. A sample of 36 elliptical galaxies is selected from the Palomar spectroscopic survey. We detect nuclear non-stellar infrared emission in nine of them. There is unambiguous evidence of circumnuclear dust in these nine galaxies in their optical images. We also find a remarkable correlation between the infrared excess emission and the nuclear radio/X-ray emission, suggesting that infrared excess emission is tightly related to nuclear activity. The possible origin of infrared excess emission from hot dust heated by the central AGN is supported by the spectral indices of the infrared excess emission.     

Far-infrared detection limits – II. Probing confusion including source confusion

We present a comprehensive analysis for the determination of the confusion levels for the current and the next generation of far-infrared surveys assuming three different cosmological evolutionary scenarios. We include an extensive model for diffuse emission from infrared cirrus in order to derive absolute sensitivity levels taking into account the source confusion noise due to point sources, the sky confusion noise due to the diffuse emission, and instrumental noise. We use our derived sensitivities to suggest best survey strategies for the current and the future far-infrared space missions Spitzer , AKARI ( ASTRO-F ), Herschel and SPICA . We discuss whether the theoretical estimates are realistic and the competing necessities of reliability and completeness. We find the best estimator for the representation of the source confusion and produce predictions for the source confusion using far-infrared source count models. From these confusion limits considering both source and sky confusions, we obtain the optimal, confusion limited redshift distribution for each mission. Finally, we predict the cosmic far-infrared background (CFIRB), which includes information about the number and distribution of the contributing sources.     

The Low Metallicity ISM of Dwarf Galaxies

The properties of the low metallicity environments of dwarf galaxies are studied through dust observations in conjunction with the FIR fine-structure cooling lines. There is a striking enhancement of the I[CII]/I(CO) in dwarf galaxies that is explained by the decreased attenuation of the UV light in molecular clouds. An important consequence is that a significant mass of the molecular gas mass inventory can be missed through CO observations alone. Modeling the infrared spectral energy distribution into submillimeter wavelengths in dwarf galaxies reveals the presence of very cold (∼ 8K) dust,which accounts for a large fraction of the dust mass, until now missed by models using IRAS observations alone. In spite of the striking defficiency of the mid-infrared aromatic band carriers, cooling in the photodissociation regions, via [CII] line emission is a very efficient process. This revised version was published online in September 2006 with corrections to the Cover Date.     

Far-infrared detection limits – I. Sky confusion due to Galactic cirrus

Fluctuations in the brightness of the background radiation can lead to confusion with real point sources. This type of confusion with background emission is relevant when making infrared (IR) observations with relatively large beam sizes, since the amount of fluctuation tends to increase with the angular scale. To quantitively assess the effect of the background emission on the detection of point sources for current and future far-IR observations by space-borne missions such as Spitzer , ASTRO-F , Herschel and Space Infrared Telescope for Cosmology and Astrophysics ( SPICA ), we have extended the Galactic emission map to a higher level of angular resolution than that of the currently available data. Using this high-resolution map, we estimate the sky confusion noise owing to the emission from interstellar dust clouds or cirrus, based on fluctuation analysis and detailed photometry over realistically simulated images. We find that the confusion noise derived by simple fluctuation analysis agrees well with the results from realistic simulations. Although sky confusion noise becomes dominant in long wavelength bands  (>100 μm)  with 60–90 cm aperture missions, it is expected to be two orders of magnitude lower for the next generation of space missions (with larger aperture sizes) such as Herschel and SPICA .     

Modelling the Spoon IRS diagnostic diagram

We explore whether our models for starbursts, quiescent star-forming galaxies and for active galactic nuclei (AGN) dust tori are able to model the full range of Spitzer Infrared Spectrograph (IRS) spectra measured with Spitzer . The diagnostic plot of 9.7 μm silicate optical depth versus 6.2 μm polycyclic aromatic hydrocarbon (PAH) equivalent width, introduced by Spoon and coworkers in 2007, gives a good indication of the age and optical depth of a starburst, and of the contribution of an AGN dust torus. However, there is aliasing between age and optical depth at later times in the evolution of a starburst, and between age and the presence of an AGN dust torus. Modelling the full IRS spectra and using broad-band 25–850 μm fluxes can help to resolve these aliases. The observed spectral energy distributions require starbursts of a range of ages with initial dust optical depth ranging from 50–200, optically thin dust emission ('cirrus') illuminated by a range of surface brightnesses of the interstellar radiation field, and AGN dust tori with a range of viewing angles.     

Millimetron—a large Russian-European submillimeter space observatory

Millimetron is a Russian-led 12 m diameter submillimeter and far-infrared space observatory which is included in the Space Plan of the Russian Federation for launch around 2017. With its large collecting area and state-of-the-art receivers, it will enable unique science and allow at least one order of magnitude improvement with respect to the Herschel Space Observatory. Millimetron will be operated in two basic observing modes: as a single-dish observatory, and as an element of a ground-space very long baseline interferometry (VLBI) system. As single-dish, angular resolutions on the order of 3 to 12 arc sec will be achieved and spectral resolutions of up to a million employing heterodyne techniques. As VLBI antenna, the chosen elliptical orbit will provide extremely large VLBI baselines (beyond 300,000 km) resulting in micro-arc second angular resolution.     

RXTE observation of NGC 6240: a search for the obscured active nucleus

We present new data taken at 850 μm with SCUBA at the James Clerk Maxwell Telescope for a sample of 19 luminous infrared galaxies. Fourteen galaxies were detected. We have used these data, together with fluxes at 25, 60 and 100 μm from IRAS , to model the dust emission. We find that the emission from most galaxies can be described by an optically thin, single temperature dust model with an exponent of the dust extinction coefficient ( k _λ ∝ λ ^{− β} ) of β ≃1.4–2. A lower β ≃1 is required to model the dust emission from two of the galaxies, Arp 220 and NGC 4418. We discuss various possibilities for this difference and conclude that the most likely is a high dust opacity. In addition, we compare the molecular gas mass derived from the dust emission, M _850 μm, with the molecular gas mass derived from the CO emission, M _CO, and find that M _CO is on average a factor 2–3 higher than M _850 μm.     

The properties of 70 μm-selected high-redshift galaxies in the Extended Groth Strip

We examine the infrared properties of 43 high-redshift (0.1 < z < 1.2), infrared-luminous galaxies in the Extended Groth Strip (EGS), selected by a deep 70 μm survey with the Multiband Imaging Photometer on Spitzer (MIPS). In addition and with reference to starburst-type spectral energy distributions (SEDs), we derive a set of equations for estimating the total infrared luminosity ( L _IR) in the range 8–1000 μm using photometry from at least one MIPS band. 42 out of 43 of our sources' optical/infrared SEDs (λ_observed < 160 μm) are starburst type, with only one object displaying a prominent power-law near-infrared continuum. For a quantitative analysis, models of radiation transfer in dusty media are fit on to the infrared photometry, revealing that the majority of galaxies are represented by high extinction, A _v > 35, and for a large fraction (∼50 per cent) the SED turns over into the Rayleigh–Jeans regime at wavelengths longward of 90 μm. For comparison, we also fit semi-empirical templates based on local galaxy data; however, these underestimate the far-infrared SED shape by a factor of at least 2 and in extreme cases up to 10 for the majority (∼70 per cent) of the sources. Further investigation of SED characteristics reveals that the mid-infrared (70/24 μm) continuum slope is decoupled from various galaxy properties such as the total infrared luminosity and far-infrared peak, quantified by the L ₁₆₀/ L ₇₀ ratio. In view of these results, we propose that these high-redshift galaxies have different properties to their local counterparts, in the sense that large amounts of dust cause heavy obscuration and are responsible for an additional cold emissive component, appearing as a far-infrared excess in their SEDs.     

Effects of massive star formation on the ISM of dwarf galaxies

We are studying star formation effects on the properties of the ISM in low metallicity environments using mid-infrared (MIR) and far-infrared (FIR) observations of starbursting dwarf galaxies taken with the Infrared Space Observatory (ISO) and the Kuiper Airborne Observatory (KAO). Effects of the hard pervasive radiation field on the gas and dust due to the dust-poor environments are apparent in both the dust and gas components. From a 158 μm [CII] survey we find enhanced I[CII]/FIR ratios in dwarf galaxies and I[CII]/I(CO) ratios up to 10 times higher than those for normal metallicity starburst galaxies. We consider MIR observations in understanding the star formation properties of dwarf galaxies and constraints on the stellar SED. Notably, the strong MIR [NeIII]/[NeII] ratios reveal the presence of current massive stellar populations <5 My old in NGC 1569, NGC 1140 and IIZw40. The MIR unidentified infrared bands (UIBs) are weak, if present at all, as a general characteristic in low metallicity environments, revealing the destruction of the smallest carbon particles (e.g. PAHs) over large spatial scales. This is confirmed with our dust modeling: mass fractions of PAHs are almost negligible compared to the larger silicate grains emitting in the FIR as well as the small carbon grains emitting in the MIR, which appear to be the source of the photoelectric gas heating in these galaxies, in view of the [CII] cooling.     

The Detection of Extremely Distant Galaxies

Very recent observations have shown that there are dusty galaxies at redshifts larger that 5. Their integrated contribution to the far-IR/submillimeter sky background is known. These galaxies are very hard to detect in the visible and in the infrared, but they will be within reach of the NGST, although it will be very difficult to recognize them without further studies. However their far-infrared emission will be detectable by FIRST and more easily by the large submillimeter interferometer (ALMA) presently under study. The ALMA, FIRST, SIRTF and the NGST will make an ideal set for investigating the formation and early evolution of galaxies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Morphology and kinematics of the ionised gas in early-type galaxies

We present results of our ongoing study of the morphology and kinematics of the ionised gas in 48 representative nearby elliptical and lenticular galaxies using the SAURON integral-field spectrograph on the 4.2m William Herschel Telescope. Making use of a recently developed technique, emission is detected in 75% of the galaxies. The ionised-gas distributions display varied morphologies, ranging from regular gas disks to filamentary structures. Additionally, the emission-line kinematic maps show, in general, regular motions with smooth variations in kinematic position angle. In most of the galaxies, the ionised-gas kinematics is decoupled from the stellar counterpart, but only some of them present signatures of recent accretion of gaseous material. The presence of dust is very common in our sample and is usually accompanied by gas emission. Our analysis of the [Oiii]/Hβ emission-line ratios, both across the whole sample as well as within the individual galaxies, suggests that there is no unique mechanism triggering the ionisation of the gas.     

The evolution of star formation in quasar host galaxies

We have used far-infrared data from IRAS , Infrared Space Observatory ( ISO ), Spitzer Wide-Area Infrared Extragalactic (SWIRE), Submillimetre Common User Bolometer Array (SCUBA) and Max-Planck Millimetre Bolometer (MAMBO) to constrain statistically the mean far-infrared luminosities of quasars. Our quasar compilation at redshifts  0 < z < 6.5  and I -band luminosities  −20 < I _AB < −32  is the first to distinguish evolution from quasar luminosity dependence in such a study. We carefully cross-calibrate IRAS against Spitzer and ISO , finding evidence that IRAS 100-μm fluxes at <1 Jy are overestimated by ∼30 per cent. We find evidence for a correlation between star formation in quasar hosts and the quasar optical luminosities, varying as star formation rate (SFR)  ∝ L ^0.44±0.07_opt  at any fixed redshift below   z = 2  . We also find evidence for evolution of the mean SFR in quasar host galaxies, scaling as  (1 + z )^1.6±0.3  at   z < 2  for any fixed quasar I -band absolute magnitude fainter than −28. We find no evidence for any correlation between SFR and black hole mass at  0.5 < z < 4  . Our data are consistent with feedback from black hole accretion regulating stellar mass assembly at all redshifts.