849 research outputs found
High Resolution WFPC2 Imaging of IRAS 09104+4109
With a infrared luminosity of nearly 10^13 Lsuns, IRAS 09104+4109 is the most
luminous galaxy with z<0.5 in the IRAS All Sky Survey. A radio-loud Seyfert 2
type optical spectrum, a cD host galaxy in a rich cluster, and a massive
cooling flow make IRAS 09104+4109 unique among ultraluminous infrared galaxies.
Cannibalized cluster members and the cooling intercluster medium may contribute
both the fuel and the dust needed to re-radiate the power of IRAS 09104+4109
into the far-infrared. We have imaged IRAS 09104+4109 in the WFPC2 F622W,
F814W, and FR680N filters on the HST to obtain rest frame 4300A, 5700A, and
[OIII] emission line images on sub-kpc scales. IRAS 09104+4109 displays a
complex morphology on the smallest scales, with radiating filaments, an
asymmetric [OIII] nebula, and a number of very faint, irregular blue objects
surrounding the cD galaxy. We discuss the nature and possible interplay between
the enshrouded QSO nucleus, the cD host galaxy and the irregular cluster.Comment: LaTex, 6 pages with 2 postscript and 1 jpg figure. To appear in the
proc. of the Ringberg workshop "Ultraluminous Galaxies: Monsters or Babies"
(Ringberg castle, Sept. 1998), Ap&SS, in pres
Near Infrared Observations of a Redshift 4.92 Galaxy: Evidence for Significant Dust Absorption
Near-infrared imaging and spectroscopy have been obtained of the
gravitationally lensed galaxy at z=4.92 discovered in HST images by Franx et
al. (1997). Images at 1.2, 1.6 and 2.2 microns show the same arc morphology as
the HST images. The spectrum with resolution \lambda / \Delta\lambda ~ 70 shows
no emission lines with equivalent width stronger than 100 A in the rest frame
wavelength range 0.34 to 0.40 microns. In particular, [OII]3727 A and
[NeIII]3869 A are not seen. The energy distribution is quite blue, as expected
for a young stellar population with the observed Ly alpha flux. The spectral
energy distribution can be fit satisfactorily for such a young stellar
population when absorption by dust is included. The models imply a reddening
0.1 mag < E(B-V) < 0.4 mag. The stellar mass of the lensed galaxy lies in the
range of 2 to 16 x 10^9 Msun. This is significantly higher than estimates based
on the HST data alone. Our data imply that absorption by dust is important to
redshifts of ~5.Comment: LaTeX with ApJ journal format, 2 postscript figures, ApJL, accepte
Near Infrared Observations of a Redshift 5.34 Galaxy: Further Evidence for Dust Absorption in the Early Universe
Imaging at 1.25 and 2.20 microns has been obtained of the field containing
the galaxy (RD1) found at redshift 5.34 by Dey et al.(1998). This galaxy has
been detected at 1.25 microns, while the lower redshift (z=4.02) galaxy also
found in the same field by Dey et al. was detected at both 1.25 and 2.20
microns. Comparison to stellar population synthesis models indicates that if
RD1 is a young ( 0.5 mag)
is indicated. Combined with observations of other high redshift systems, these
data show that dust is likely to be an important component of young galaxies
even at redshifts of z > 5. The extinction-corrected monochromatic luminosity
of RD1 at 1500 angstroms is then a factor of about three larger than L(1500)*
as determined by Dickinson (1998) for z ~ 3 starburst galaxies. The implied
star formation rate in RD1, corrected for extinction, is ~ 50-100 solar masses
per year.Comment: plain LaTex with 1 postscript figure. ApJ Letters, accepte
Infrared Astronomy
Several observational programs in infrared astronomy are described and significant findings are briefly discussed. The near infrared work concentrates largely on the use of the 5 m Hale telescope in spectroscopic and photometric studies of extragalactic sources. Observations of the P alpha line profile in a low redshift quasar, X-ray bursters, reflection nebula, and cataclysmic variables are included. Millimeter continuum observations of dust emission from quasars and galactic molecular clouds are also discussed. Finally, improvements to instrumentation are reported
Infrared properties of serendipitous X-ray quasars
Near infrared measurements were obtained of 30 quasars originally found serendipitously as X-ray sources in fields of other objects. The observations show that the infrared characteristics of these quasars do not differ significantly from those of quasars selected by other criteria. Because this X-ray selected sample is subject to different selection biases than previous radio and optical surveys, this conclusion is useful in validating previous inferences regarding the infrared colors of 'typical' quasars
The properties of infrared galaxies in the local universe
The 60 µm selected IRAS Bright Galaxy Sample is used as a starting point to derive additional complete flux-limited samples of extragalactic objects at 12, 25, and 100 µm. With these complete samples the luminosity functions at all IRAS wavelengths are derived for the local Universe. These luminosity functions are used to determine the infrared emission of the local Universe. The maximum in the energy output of galaxies occurs at 100 µm. The infrared emission of galaxies at 12 and 25 µm represents
~30% of the total infrared luminosity in the local Universe. The mean infrared colors of infrared selected galaxies vary systematically with infrared luminosity; the ratio S^v(60 µm)/S_v( 100 µm) increases and S_v(12 µm)/Sv(25 µm) decreases with increasing infrared luminosity
A new luminosity component in 3C 48
The infrared emission from the quasar 3C 48 has a luminosity L ≃ 5 x 10^(12) L_☉ and dominates the power output of the quasar system. It is shown that the infrared emission, unlike that of most radio-loud quasars, is most likely not an extension of the radio emission of the quasar. It is argued that the infrared emission in 3C 48 is probably thermal radiation arising in a highly luminous galaxy surrounding the quasar
Extremely Luminous Far-infrared Sources (ELFS)
The Infrared Astronomical Satellite (IRAS) survey uncovered a class of Extremely Luminous Far Infrared Sources (ELFS), exhibiting luminosities up to and occasionally exceeding 10 to the 12th power L sub 0. Arguments are presented to show that sources with luminosities L equal to or greater than 3 x 10 to the 10th power L sub 0 may represent gas rich galaxies in collision. The more conventional explanation of these sources as sites of extremely active star formation fails to explain the observed low optical luminosities of ELFS as well as their high infrared excess. In contrast, a collisional model heats gas to a temperature of approx. 10 to the 6th power K where cooling takes place in the extreme ultraviolet. The UV is absorbed by dust and converted into far infrared radiation (FIR) without generation of appreciable optical luminosity. Gas recombination as it cools generates a Lyman alpha photon only once for every two extreme ultraviolet approx. 50eV photons emitted by the 10 to the 6th power gas. That accounts for the high infrared excess. Finally, the model also is able to explain the observed luminosity distribution of ELFS as well as many other traits
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