The IRAS bright galaxy sample. II - The sample and luminosity function

Soifer, B. T.; Sanders, D. B.; Madore, B. F.; Neugebauer, G.; Danielson, G. E.; Elias, J. H.; Lonsdale, C. J.; Rice, W.

doi:10.1086/165536

Cited by 481 publications

(496 citation statements)

References 12 publications

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“…The former-which means no observable recent high-mass SFleads to old stellar populations (II) and low emission levels in most wavebands (except those tracing gas in low excitation conditions, i.e., the neutral atomic and molecular phases, and old stars). The latter-which characterizes a starburst (Soifer et al 1987b)-leads to the presence of hot young stars (population I) with blue color. SF is going on at such a high rate that it cannot be maintained over a Hubble time (i.e., the age of the Universe), implying that it must be a transient phenomenon.…”

Section: Starburst Vs Normal Galaxiesmentioning

confidence: 99%

Gaseous Halos of Late-Type Spiral Galaxies

Dahlem¹

1997

PASP

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ABSTRACT. This article reviews the most recent observational results on disk-halo interactions in nearby galaxies. The implications of these results on our understanding of the structure of the interstellar medium (ISM) in our Galaxy and external spiral galaxies, with particular emphasis on the halo ISM, are discussed. Disk-halo interactions occur only above the brightest HII regions, which are found almost exclusively in late-type spirals and dwarf and irregular galaxies. Circumnuclear starbursts are the most energetic flavor of this phenomenon. The existence, the shapes, and the properties of gaseous halos depend on the level of energy input into the disk ISM per unit surface area, i.e., on the feedback of mass, momentum, and energy produced by vigorous star formation. Thus, current theoretical models of the ISM take into account that gaseous halos are natural extensions of disk ISMs and are heated by the winds and ionizing radiation of massive stars, and by the shock waves of Supernovae and their remnants. Observationally, this is reflected by the fact that all phases of the ISM known to exist in galaxy disks have also been detected in halos. Disk-halo interactions are a very effective way of redistributing energy, metals, and magnetic fields in galaxies and of expelling them into intergalactic space when outflows reach escape velocity. MOTIVATION AND OUTLINESpiral galaxies consist of three spatially and dynamically dinstinct components, namely bulge, disk, and halo. Of these, the central bulge consists primarily of old stars and has a low gas fraction. The disk and halo consist of stars plus gas, dust, and in many cases "dark matter." Here I want to concentrate on the interstellar medium (ISM) in the disks and halos of galaxies, with emphasis on late-type spirals. Massive dark halos will not be described (see, e.g., Ashman 1992; Holt and Bennett 1995). In the current context "latetype" stands for disk-dominated spirals with rather inconspicuous bulges (Hubble types Sb -Sdm). The ISM of elliptical galaxies and early-type spirals (S0-Sab) will also not be presented here (cf. Walsh et al. 1989;and Fabbiano 1989).Studies of the ISM contribute significantly to our understanding of the structure, kinematics, and evolution of galaxies. The level of star formation (SF), its spatial distribution, and its temporal changes depend strongly on the properties of the interstellar gas from which stars can form. Stars feed energy and metal-enriched matter back into the ambient medium via stellar winds and supernovae (SNe), thereby distributing processed material throughout the ISM. Hence, through this gas-star-gas cycle, the ISM becomes a mediator of SF.In Sec. 2, the different phases of the ISM in galaxies will be introduced, and Sec. 3 presents observations of the ISM in the Milky Way. Section 4 will show that the Galactic ISM is l A\\ correspondence should be directed to this address. not confined to the thin disk, but extends to high distances (z) above the plane, forming a gaseous halo. However, being located within the...

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Section: Starburst Vs Normal Galaxiesmentioning

confidence: 99%

Gaseous Halos of Late-Type Spiral Galaxies

Dahlem¹

1997

PASP

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“…The first extensive survey of the mid-to far-infrared sky was made by the IRAS mission launched in 1983 (Neugebauer et al 1984). IRAS surveyed 87% of the sky in four photometric bands at 12 μm, 25 μm, 60 μm and 100 μm and substantially pioneered the various new fields of astronomy, like circumstellar debris disks around Vegalike stars (Aumann et al 1984) and a new class of galaxies that radiate most of their energy in the infrared (Soifer et al 1987).…”

Section: Introductionmentioning

confidence: 99%

The AKARI/IRC mid-infrared all-sky survey

Ishihara

Onaka

Kataza

et al. 2010

A&A

544

249

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Context. AKARI is the first Japanese astronomical satellite dedicated to infrared astronomy. One of the main purposes of AKARI is the all-sky survey performed with six infrared bands between 9 μm and 200 μm during the period from 2006 May 6 to 2007 August 28. In this paper, we present the mid-infrared part (9 μm and 18 μm bands) of the survey carried out with one of the on-board instruments, the infrared camera (IRC). Aims. We present unprecedented observational results of the 9 μm and 18 μm AKARI all-sky survey and detail the operation and data processing leading to the point source detection and measurements. Methods. The raw data are processed to produce small images for every scan, and the point sources candidates are derived above the 5σ noise level per single scan. The celestial coordinates and fluxes of the events are determined statistically and the reliability of their detections is secured through multiple detections of the same source within milli-seconds, hours, and months from each other. Results. The sky coverage is more than 90% for both bands. A total of 877 091 sources (851 189 for 9 μm, 195 893 for 18 μm) are confirmed and included in the current release of the point source catalog. The detection limit for point sources is 50 mJy and 90 mJy for the 9 μm and 18 μm bands, respectively. The position accuracy is estimated to be better than 2 . Uncertainties in the in-flight absolute flux calibration are estimated to be 3% for the 9 μm band and 4% for the 18 μm band. The coordinates and fluxes of detected sources in this survey are also compared with those of the IRAS survey and are found to be statistically consistent.

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“…Local Ultra-Luminous Infrared Galaxies (ULIGs) found by the IRAS survey (Soifer et al 1987) are divided into warm and cold objects based on their infrared colours. It has been known through optical spectroscopic surveys that warm IRAS objects tend to host Seyfert nuclei (e.g., De Grijp et al 1985) while cold IRAS objects are usually star-forming galaxies.…”

Section: X-ray Properties Of Luminous Infrared Galaxiesmentioning

confidence: 99%

The Obscured AGN Population Probed by X-ray Observations

Iwasawa

2002

International Astronomical Union Colloquium

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Abstract. X-ray properties of obscured AGN are reviewd and recent results obtained from ASCA, BeppoSAX, and Chandra are presented.There is a population of AGN that can only be revealed by hard X-ray observations. Studies of the X-ray background suggest that obscured AGN should significantly outnumber their unobscured counterparts. X-ray Spectra of Obscured AGN Effects of X-ray AbsorptionThe energy distribution of AGN can be approximated by a power-law and is roughly fiat over the X-ray band. However, we now know at least in wellstudied bright Seyfert galaxies that there are a significant excess of soft X-ray (below half keV) emission and a roll-over of the hard X-ray continuum at a few hundred keV. The soft X-ray excess is believed to be related to the accretion disk while the high energy roll-over is probably due to a cut-off in energy of thermal electrons in a corona which Comptonizes the disk emission into the power-law continuum. There are other subtle spectral distortions due to reflection off the accretion disk surface. These phenomena are likely happening in a region within 100 gravitational radii of a central black hole.When cold matter lies in the line of sight at radii much further out, a series of photoelectric edges of various elements as well as Hydrogen are imposed on the X-ray continuum and make a low energy cut-off. The energy of the absorption cut-off increases as the column density of the absorbing matter increases. Therefore, going up across the X-ray energy band has the same effect as increasing wavelength in the optical/near-infrared for obscured objects. Assuming the Galactic dust to gas ratio, the optical depth which a near-infrared observation (say, in the K band) can probe is equivalent to that at 2-3 keV. For example, ROSAT, whose bandpass was up to 2 keV, was sensitive to relatively unobscured AGN but no longer sensitive when an absorption column density exceeds 10 22 cm -2 (of course, this restriction is relaxed for high redshift objects). X-ray observatories such as ASCA, BeppoSAX, Chandra and XMMNewton have sensitivity above 2 keV, which enables these satellites to search for highly obscured AGN. It should, however, be noted that simply shifting the energy window to higher energies does not necessarily guarantee detection of more heavily obscured objects, because of a) increasing importance of Comp- 225terms of use, available at https://www.cambridge.org/core/terms. https://doi

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The IRAS bright galaxy sample. II - The sample and luminosity function

Cited by 481 publications

References 12 publications

Gaseous Halos of Late-Type Spiral Galaxies

Gaseous Halos of Late-Type Spiral Galaxies

The AKARI/IRC mid-infrared all-sky survey

The Obscured AGN Population Probed by X-ray Observations

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