Radio AGNs among Luminous Infrared Galaxies

An analysis of radio and FIR emission in over 1500IRAS selected galaxies produces a good linear correlationbetween radio and FIR luminosity, indicating that star formationin normal field galaxies dominates the infrared luminosityin the local volume. Galaxies with clear radio-excess (definedas having at least5 times larger radio flux over expected from FIR) are identified as hosting a radio AGN, and they account for onlyabout 1% of the whole sample. This fraction increases to 10% among themore luminous galaxies with L _1.4GHz 10²³ W Hz^-1 (equivalently L _60m 10¹¹ L), however. The characteristic mid-IR excess of a Seyfert nucleus is ubiquitously present amongthe radio-excess objects, suggesting that mid-IR excess isa robust tracer of an AGN despite the high mid-IR opacity.We conclude that about 30% of the luminous infrared galaxies(L _60m 10¹¹ L) host an AGN based on themid-IR excess, and about 40% of the mid-IR excess AGNs alsohost a radio AGN. A VLA imaging survey of a distance limited sample of IR luminousgalaxies has revealed the presence of 100 kpc scale giant radioplumes in 3 out of 9 cases (Mrk 231, Mrk 273, NGC 6240). Theirlarge spatial extent, energetics, and presence of a powerful AGN in each case suggests that an AGN is the power source. Such plumesare not detected in other ultraluminous infrared galaxies which lack clear evidence for an AGN, such as Arp 220.     

Extinction and scattering by several types of silicate sphere of radius 0.05–1.0μm,for the wavelength range 0.21–50μm

The exact calculation of scattering and absorption by various sub-micron sized silicate spheres is presented here, using accurately determined optical constants in the wavelength range from 50 m to 0.21 m. The extinction features near 10 m and 20 m for various samples are discussed. It is found that the ratio of peak extinction at 20 m to that at 10 m is constant for small particles up tor=0.4 m, but is less for particles of radius 1 m. The ratio of maximum extinction in the ultraviolet to that at 10 m decreases with increasing particle size.     

A high resolution mid-infrared image of the Starburst Galaxy M82

We have produced high-resolution images of the nuclear region of M82 with SpectroCam-10, a mid-infrared instrument at the Palomar 5 m telescope. These images were taken at 11.7 m and 9.8 m with a 1m filter bandpass at the diffraction limit of 0.6 arcsec, making them the highest resolution maps yet available of M82. In addition, we have obtained high-resolution (/=2000) maps of the velocity field of the nuclear disk of M82 in the 12.81 m line emission of [NeII]. In these proceedings we present the 11.7 m image, which will appear together with the 9.8 m map and the [Ne II] spectra in a subsequent paper, now in preparation. This image shows very clearly a bridge structure joining the eastern and western clusters.     

Circumstellar dust shells around very young and massive stars

In this paper we investigate the properties of dust in circumstellar shells around very young massive compact IR sources (Becklin-Neugebauer objects).We found no correlation between the optical depth in the centre of the 10-m band and the 3.1-m ice band. An inverse correlation between the strength of the silicate feature and the colour temperature for the 8–13 m interval was detected. Our sample of BN objects extends this kind of relation already known for Mira stars and OH/IR stars to higher optical depths.We present a radiative transfer model for BN objects and discuss its main properties. Using this model, the interpretation of the observations led to the conclusion that the type of silicates present in the dust shells of very young stellar objects is different from that type around oxygen-rich giants and supergiants. These different silicates may be tentatively identified with pyroxenes and olivines, respectively.We studied the influence of the adopted dust model in deriving source parameters of BN objects. The object W3-IRS5 was discussed in some detail.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986.     

Charge-coupled device imaging spectroscopy of Mars. 1. Instrumentation and data reduction/analysis procedures

This paper describes the collection, reduction, and analysis of 0.4–1.0 m Mars imaging spectroscopy data obtained during the 1988 and 1990 oppositions from Mauna Kea Observatory and provides a general outline for the acquisition and analysis of similar imaging spectroscopy data sets. The U.H. 2.24-m Wide Field Grism CCD Spectrograph was used to collect 13 three-dimensional image cubes covering 90% of the planet south of 50°N in the 0.4–0.8 m region (/=245 at 0.6 m) and covering 55% of the planet south of 50°N in the 0.5–1.0 m region (/=293 at 0.75 m). Spectra extracted from these image cubes reveal the detailed character of the martian near-UV to visible spectrum. Images at red wavelengths reveal the classical albedo markings at 100–500 km spatial resolution while images at blue wavelengths show little surface feature contrast and are dominated by condensate clouds/hazes and polar ice. Many of the data acquisition, reduction, and analysis steps discussed here are new or unique to imaging spectroscopy data sets. These techniques exploit the information contained within the spatial domain of data such as these, thus allowing more traditional point-spectral analysis techniques to be expanded into an imaging format.     

Astronomical imaging with InSb arrays

Ten years ago, Forrest presented the first astronomical images with an SBRC 32×32 InSb array camera at the first NASA-Ames Infrared Detector Technology Workshop. Soon after, SBRC began development of 58×62 InSb arrays, both for ground-based astronomy and for SIRTF. By the time of the 1987 Hilo workshop Ground-based Astronomical Observations with Infrared Array Detectors astronomical results from cameras based on SBRC 32×32 and 58×62 InSb arrays, a CE linear InSb array, and a French 32×32 InSb CID array were presented. And at the Tucson 1990 meeting Astrophysics with Infrared Arrays, it was clear that this new technology was no longer the province of IR pundits, but provided a tool for all astronomers. At this meeting, the first astronomical observations with SBRC's new, gateless passivation 256×256 InSb arrays will be presented: they perform spectacularly!In this review, I can only broadly brush on the interesting science completed with InSb array cameras. Because of the broad wavelength coverage (1–5.5 m) of InSb, and the extremely high performance levels throughout the band, InSb cameras are used not only in the near IR, but also from 3–5.5 m, where unique science is achieved. For example, the point-like central engines of AGNs are delineated at L and M, and Br and 3.29 m dust emission images of galactic and extragalactic objects yield excitation conditions. Examples of imaging spectroscopy, high spatial resolution imaging, as well as deep, broad-band imaging with InSb cameras at this meeting illustrate the power of InSb array cameras.     

Infrared emission of dust grains in the clusters of galaxies

The observations of the reddening of the distant galaxies and the weak diffuse radiation in the clusters of galaxies can be interpreted as a consequence of the presence of dust grains in the intergalactic medium. When allowance is made for the destruction of the grains in collision with particles of the hot gas, its lifetime is about 10⁷–10⁸ yr at a gas concentrationn _g 10^–3 cm^–3. The detection of the infrared (IR) emission from the galaxy clusters might be the test for the proof of the presence of dust grains in the intergalactic medium. In this paper the estimates of the expected intensities and fluxes of IR emission for the spectral region 50–300 are presented for two galaxy clusters in Coma and Perseus. The parameters of the hot gas spatial distribution are chosen from X-ray observations. Having assumed that intergalactic dust can be ejected only from the galaxies, we used such a model for intergalactic dust grains which explains very well the interstellar dust effects. It is shown that the dust temperature, which is determined from the general energetic balance of the dust grains, can achieve some scores of degrees of Kelvin. Two models of the dust spatial distribution are considered. It is found that the maximum of IR flux for the Coma cluster lies near =100 and the same for the Perseus cluster near 50–70. The total fluxes of IR emission from these clusters are about 10⁵–10⁶ Jy and can be detected by modern observational methods.     

Far-infrared emission from an intergalactic dust cloud?

We used theIRAS All Sky Maps in order to search for infrared emission in the direction of the Okroy Cloud (R.A.=12^h50^m, =22°). An enhancement of 100 m diffuse emission is evident in such a region, with an anomalous value of the ratioI _v (100 m)/A _v ; hydrogen 21 cm emission is also present with low radial speed, thus suggesting that the cloud could be a satellite of our Galaxy.     

Ultraviolet observations of β Persei, μ1 Scorpii and γ2 Velorum with the TD-1A satellite

This paper reports on the results of a study of S59 ultraviolet spectral scans of the spectroscopic binaries Persei, ¹ Scorpii and ₂ Velorum. In the case of ¹ Sco it was found that the Mgii doublet at 2800 Å undergoes intensity variations that may be indicative of variable emission in the photographic spectrum. The continuum in the 2490–2590 Å range deviates from the continuum of the comparison stars. In ₂ Vel, flux variations in the 2770–2870 Å region have been detected.Member of the Carrera del Investigador Cientifico, CONICET, Argentina. Guest Investigator of the S59 experiment on board the TD-1A satellite.     

Continuum radiation from active galactic nuclei

Summary Active galactic nuclei (AGN) can be divided into two broad classes, where the emitted continuum power is dominated either by thermal emission (radio-quiet AGN), or by nonthermal emission (blazars). Emission in the 0.01–1 m range is the primary contributor to the bolometric luminosity and is probably produced through thermal emission from an accretion disk, modified by electron scattering and general relativistic effects. The 1–1000 m continuum, the second most important contributor to the power, is generally dominated by thermal emission from dust with a range of temperatures from 40 K to 1000–2000 K. The dust is probably reemitting 0.01–0.3 m continuum emission, previously absorbed in an obscuring cone (or torus) or an extended disk. The 1–10 keV X-ray emission is rapidly variable and originates in a small region. This emission may be produced through Compton scattering by hot thermal electrons surrounding an accretion disk, although the observations are far from being definitive. The weak radio emission, which is due to the nonthermal synchrotron process, is usually elongated in the shape of jets and lobes (a core may be present too), and is morphologically distinct from the radio emission of starburst galaxies.In the blazar class, the radio through ultraviolet emission is decidedly non-thermal, and apparently is produced through the synchrotron process in an inhomogeneous plasma. The plasma probably is moving outward at relativistic velocities within a jet in which the Lorentz factor of bulk motion (typically 2–6) increases outward. This is inferred from observations indicating that the opening angle becomes progressively larger from the radio to the optical to the X-ray emitting regions. Shocks propagating along the jet may be responsible for much of the flux variability. In sources where the X-ray continuum is not a continuation of the optical-ultraviolet synchrotron emission, some objects show variability consistent with Compton scattering by relativistic electron in a large region (in BL Lacertae), while other objects produce their X-ray emission in a compact region, possibly suggesting pair production.When orientation effects are included, all AGN may be decomposed into a radio-quiet AGN, a blazar, or a combination of the two. Radio-quiet AGN appear to have an obscuring cone or torus containing the broad emission line clouds and an ionizing source. Most likely, the (non-relativistic) directional effects of this obscuring region give rise to the difference between Seyfert 1 and 2 galaxies or narrow and broad line radio galaxies. For different orientations of the nonthermal jet, relativistic Doppler boosting can produce BL Lacertae objects or FR I radio galaxies, or at higher jet luminosities, flat-spectrum high-polarization quasars or FR II radio galaxies.     

Laboratory simulation of infrared astrophysical features

Laboratory infrared emission and absorption spectra have been taken of terrestrial silicates, meteorites and lunar soils in the form of micrometer and sub-micrometer grains. The emission spectra were taken in a way that imitates telescopic observations. The purpose was to see which materials best simulate the 10 m astrophysical feature.The emission spectra of dunite, fayalite and Allende give a good fit to the 10 m broadband emission feature of comets Bennett and Kohoutek. A study of the effect of grain size on the presence of the 10 m emission feature of dunite shows that for particles larger than 37 m no feature is seen.The emission spectrum of the Murray meteorite, a Type 2 carbonaceous chondrite, is quite similar to the intermediate resolution spectrum of comet Kohoutek in the 10 m region. Hydrous silicates or amorphous magnesium silicates in combination with high-temperature condensates, such as olivine or anorthite, would yield spectra that match the intermediate resolution spectrum of comet Kohoutek in the 10 m region. Glassy olivine and glassy anorthite in approximately equal proportions would also give a spectrum that is a good fit to the cometary 10 m feature.Invited contribution to the Proceedings of a Workshop onThermodynamics and Kinetics of Dust Formation in the Space Medium held at the Lunar and Planetary Institute, Houston, 6 8 September, 1978.     

A sky-noise measurement and its implication for ground-based infrared astronomy in the 10μm atmospheric window

A spectral analysis of the fluctuations of the infrared sky radiance at 10m was made at the ESO-site of La Silla in Northern Chile. The data are compared to literature. The consequences of the results on infrared observing for future large telescopes are discussed: our data suggest that in order to achieve background noise limited performance in the 10m atmospheric window chopping with frequencies of 8 Hz and amplitudes of 10 arcsec is mandatory.based on observations obtained at the European Southern Observatory, La Silla, Chile     

Arome,a balloon-borne instrument for astronomical near-infrared spectrophotometry

We present here the French balloon-borne experiment named AROME. This astronomical instrument is specifically designed for the detection of near infrared emission bands (=3–12m) from extended sources of low surface brightness with an angular resolution of 0.5°. The rms sensitivity achieved is of the order of 10^-8 Wm^-2sr^-1, in terms of the power radiated in the 3.3m band. We recall that this program led to the first detection of the 3.3m feature in the spectrum of the diffuse galactic emission. The scientific results were presented and interpreted in Paper I, Giard et al., 1989. Future work will include both the observation of fainter objects at 3.3m and the detection of other emission bands at 6.2 and 11.3m.     

Iras observations of solar-like stars

IRAS has detected 70% of the 66 F, G, K nearby dwarf stars investigated here. The sample included chromospherically active as well as non-active dwarfs. The detected stars show emission at 12 and 25 m. Their 12 m luminosity is in the range 1–13×10³⁰ erg s^–1 and it is strongly correlated to the star's total luminosity (L _bol).There are indications that some of the stars possess IR emission in excess of that expected from a stellar photosphere.Paper presented at the 11th European Regional Astronomical Meeting of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Early cosmological models in Lyra's geometry

A spatially homogeneous and isotropic Robertson-Walker model withzero-curvature of the universe is studied within the frame-work of Lyra'smanifold. The gauge-function in Lyra's manifold is taken to betime-dependent. Exact solutions of Einstein equations are obtained for twodifferent early phases of the universe viz. Inflationary phase andradiation-dominated phase by using `gamma-law' equation of statep = ( - 1) . The -index, describing the material content,varies continuously with cosmic time so that in the course of itsevolution, the universe goes through a transition from an inflationaryphase to a radiation-dominated phase. The physical properties of themodels are also discussed.     

Observationally-based infrared efficiencies and planck means for circumstellar dust grains

In this paper the mean relative efficiency factors for absorption of dust grains in the wavelength range from 8 to 22 m have been derived from IR spectra of the optically thin dust shells surrounding the O-rich supergiants Cep, Ori, X Her, and R Cas. The resulting absorption efficiency curve has been extrapolated into the near as well as the far infrared regions, having regard to restrictions set by experience. Planck mean efficiency factors have been calculated for the temperature range from 30 to 1500 K. The curveQ _P(T), which shows a maximum atT=300 K, has been approximated conveniently by a power law on either side of this maximum.     

Subarcsec 10μm imaging of bipolar flow sources

We have started a program of high-resolution (0.4/pixel) 10m imaging of bipolar outflow sources using the 10m camera CAMIRAS. We present recent results obtained at the Canada France Hawaii Telescope which reveal extended emission or IR companions in several luminous objects. The extended emission we detected probably arises from transiently heated very small grains, while the newly discovered companions could contribute significantly to the outflow activity and extended far-IR emission usually attributed to the main optical source.     

A new method for determining the internal rotational angular velocity of the stars

Infrared spectra of submicrometre-sized particles of several protosilicates have been used to derive mass absorption coefficients. These data have been applied in order to describe the infrared radiation from the source OH 26.5+0.6 in terms of a simple model. A good fit of the 10 m absorption feature could be achieved, but some discrepancies remain in the 20 m region. The reasons for the weakness of the 20 m band in infrared sources are discussed.The laboratory spectra revealed that the samples contained a small admixture of carbonates. Thus, some statements about the infrared spectrum of submicrometre-sized carbonate particles could also be made.     

Stability of and motion aboutL 4 at three-to-one commensurability

The stability ofL ₄ and the motion aboutL ₄ in the restricted problem of three bodies is investigated when there is three-to-one commensurability between the long and short periods of motion, that is, when the mass ratio has the value =0.013516.... The two time scale method is used (1) to show thatL ₄ is an unstable equilibrium point when =₃, (2) to determine for what initial conditions periodic orbits occur when ₃, (3) to determine the stability of the periodic orbits, and (4) to investigate the boundedness of the motions aboutL ₄ when ₃.     

The mid-IR radio correlation at high angular resolution: NGC253

We present high angular resolution (1.2), narrow band (/=0.1) images of the nucleus of NGC253 at three wavelengths in the mid-IR (8.5, 10.0, and 12.5 m). We find that most of the mid-IR flux in the nucleus of NGC253 derives from a very small region 120 pc in diameter. Within this small region there are three spatially and spectrally distinct IR components: two bright compact sources, and a surrounding envelope of low level, diffuse emission. The mid-IR and 6cm radio are loosely correlated in position but not in brightness. The implication is that the mid-IR - radio correlation may begin to break down on small spatial scales relevant to individual star forming regions and large individual sources. These variations in the mid-IR spectra and in the radio-IR correlation imply that the nuclear emission is excited by more than one mechanism and source type.