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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Ground-based 1- to 32-microns observations of ARP 220: Evidence for a dust-embedded AGN?

New observations of the 10 and 20 micron size of the emission region in Arp 220 are presented. Also given are ground based photometry from 1 to 32 micron including measurements of the strength of the silicate feature at 10 micron. The results show that the 20 micron size of Arp is smaller than 1.5 arcsec (500 pc); comparison of IRAS and ground based observations show that IRAS 12 micron flux measured with a large arcmin beam is the same as that seen from the ground with a 3 arcsec aperture. At 10 micron a deep silicate absorption feature is seen that corresponds to a visual extinction of about 50 mag. These results suggest that a very significant portion of the 10 to the 12th power L sub 0 infrared luminosity from Arp 220 comes from a region less than or of the order of 500 pc in diameter. When these results are combined with recent measurement of a broad Brackett alpha line by DePoy and an unresolved 2.2 micron source by Neugebauer, Matthews and Scoville, a very attractive possibility for the primary luminosity source Arp 220 is a dust embedded compact Seyfert type nucleus.

Becklin, E. E.↗
NASA NTRS1987

A near-infrared study of the luminous merging galaxies NGC 2623 and Arp 148

A broad-band spectral decomposition method has been developed to determine the contributions of evolved stars, H II regions, warm dust, and obscuration to the near-infrared continuum in interacting systems. The multicolor decomposition is applied to near-infrared measurements of the long-tailed galaxy NGC 2623 and the ring system Arp 148 to determine the galactic structure and to delineate regions of galactic activity. The infrared analysis confirms that these galaxies are coalescing; since a single nucleus is observed in the infrared, the merger must be complete. Arp 148 is found to be the product of a close collision of two galaxies, and the multicolor analysis implies that this system is in an early stage of coalescence. A substantial fraction of the nuclear regions of Arp 148 and NGC 2623 may be attributed to the presence of young stars.

Joy, Marshall↗
NASA NTRS1988

Luminous extranuclear star formation in the interacting galaxy Arp 118 - NGC 1143/44

The interacting system Arp 118 (NGC 1143/44) has been observed at infrared and radio wavelengths. The interaction has produced a pair of distorted loops and several luminous radio and infrared sources in NGC 1144 which emit a total power of 2.5 x 10 to the 11th lunar masses, 80 percent of which is reradiated in the thermal infrared. Remarkably, the present observations reveal that much of the midinfrared emission originates in an extra-nuclear star-forming region. Arp 118 has many of the same characteristics as the well-studied interacting system Arp 299 (NGC 3690), including luminous extranuclear activity; the main difference between the two systems is that the nuclei of NGC 1143/44 are much less luminous at 10 microns than their counterparts in NGC 3690.

Joy, Marshall↗
NASA NTRS1989

An infrared study of starbursts in the interacting galaxy pair Arp 299 (NGC 3690+IC 694)

Extensive infrared observations have been obtained of the three active regions in Arp 299. Multiaperture JHK photometry reveals that the colors of the three regions are totally different from each other, and that there are very red nuclei smaller than 4 arcsec in two of them. Multiaperture spectroscopy of the Br-gamma and the shock-excited H2 lines shows that both the atomic and molecular lines are spatially extended, indicating that Arp 299 is undergoing an active episode of star formation not only in its nuclei but also well outside of them. Although there is some evidence that suggests the presence of a compact, active galactic nucleus, a simple starburst model can explain the bolometric luminosities, production rates of ionizing photons, and H24 line luminosities of each active region in Arp 299. However, each starburst cannot last longer than 10 to the 8th yr.

Nakagawa, Takao↗
NASA NTRS1990

A multi-frequency study of the peculiar interacting system Arp 206

Arp 206 is a nearby, relatively large, and bright interacting system comprising unequal members: NGC 3432 and UGC 5983. A third anonymous galaxy, Arp 206c, is visible in the field. The CCD images show a well-developed bridge between NGC 3432 and UGC 5983. On the other hand, the complex H I tails are not visible in the optical. In the total H I map, the bridge is lost in a general envelope encompassing both galaxies. The bridge also appears to have some radio emission. On the Total H I map the system is rather edge-on, far more than it would appear in optical wavelengths. UGC 5983 falls exactly in line with NGC 3432. The velocity of the centers of mass of NGC 3432 and UGC 5983 are 530 km s(exp -1) and 630 km s(exp -1), respectively. In view of the considerable damage sustained by NGC 3432 and the apparent low mass of UGC 5983, it appears that the passage must have been at near parabolic speed, with a small pericentric distance and a very low inclination with rspect to the disk of NGC 3432. The apparent distribution of H I along the z axis of the galaxy could be accounted for by projection effects. The tidal appendage found at higher velocities, which rises at a P.A. approx. equal to 25 degrees west of the main body of the galaxy is probably the tail, the part of the tidal damage away from the perturbing companion. The bridge may be rising north-east from the galaxy and then continue under to the south of the galaxy. The relative sizes of the appendages would indicate that the pericenter was crossed recently. Any further inferences about the collision parameters will need to await the results of detailed computational modelling of the interaction. The authors also summarize the observational characteristics of NGC 3432, UGC 5983, and Arp 206c.

Noreau, Louis↗
NASA NTRS1990

Structural and electronic changes in the growth of mercury overlayers on Cu(001) - A helium beam scattering, LEED and ARPES study

We used ABS, LEED and angle-resolved photo-electron spectroscopy (ARPES) to study bilayer films of Hg on Cu(001). In the surface temperature range of 180 to 330 K, the first Hg layer forms two ordered phases, a c(2x2) (with coverage-0.5 of Cu(001)) and a high density (partially commensurate) c(4x4) (coverage-0.62). ARPES data show that there is little or no dispersion of the 5d band of Hg. ABS data show that this layer is not flat, with in-registry Hg atoms lying about 0.15 below the not-in-registry Hg atoms. From ABS we find that the second layer forms a completely registered c(4x4) phase. From ARPES we obtain that the second layer has an electronic structure, particularly the 5d levels, characteristic of bulk mercury. Preliminary results of calculations of the structure of the bilayer are given.

Vidali, G.↗
NASA NTRS1995

Near-infrared (Fe II) and Pa Beta imaging and spectroscopy of Arp 220

We have imaged the ultraluminous infrared galaxy Arp 220 in light of the near-infrared (Fe II) 1.257 micron and Pa-beta lines, and have obtained spectra in the J- and H-band atmospheric windows. Arp 220 is a strong source of (Fe II) and Pa-beta emission, with luminosities of 1.3 x 10(exp 41) and 9.2 x 10(exp 40) ergs/s, respectively. The (Fe II) and Pa-beta emission are both extended over the central 2 sec-3 sec, but with different morphologies. We suggest that the extended (Fe II) emission is produced through the interaction of fast shocks with ambient gas in the interstellar medium (ISM) at the base of the outflowing, supernovae-driven superwind mapped by Heckman et al. (1987). The bolometric luminosity of the starburst required to power this wind is estimated to be at least 2 x 10(exp 11) solar luminosity. If the spatially unresolved (Fe II) emission is produced via a large number of supernova remnants, the implied rate is approximately 0.6/yr. The overall luminosity of such a starburst could account for a large fraction (1/2-1/3) of the Arp 220 energy budget, but the large deficit of ionizing photons (as counted by the Pa-beta luminosity) requires that the starburst be rapidly declining and/or have a low upper mass cutoff. Alternatively, dust may effectively compete with the gas for ionizing photons, or much of the ionizing radiation may escape through 'holes' in the ISM. It is also possible that a buried active galactic nuclei (AGN) produces a large fraction of the unresolved (Fe II) and Pa-beta emission. We briefly discuss these possibilities in light of these new imaging and spectroscopic data.

Armus, L.↗
NASA NTRS2003

Discovery of an Obscured Supernova in Arp 299

The galaxy merger Arp 299, at a distance of 40 Mpc, is one of the most extensively studied interacting starburst galaxies known. It has been the site of 4 known supernovae (SNe) since 1990. Arp 299 contains a number of strong radio and infrared condensations, with the strongest starburst occurring in 'Source A,' in the nuclear region of the eastern galaxy. Source A has an inferred supernova rate of 0.5-0.7/yr, and its star formation peaked 6-8 Myr ago. Our recent observations identify a new radio-loud SN in Source A, which occurred sometime between April 2002 and February 2003. We imaged Arp 299 at milliarcsecond resolution at two epochs, in April 2002 and February 2003, using the Very Long Baseline Array and (at the first epoch) the Green Bank Telescope. In 2002, four compact radio sources were found in Source A at 2.3 GHz, with flux densities ranging from 0.3 to 1.7 mJy. In 2003, 8.4 GEz images revealed a new 3 mJy source, as well as the four objects detected a year earlier. The new radio SN is more than 1000 times more powerful than the galactic supernova remnant Cassiopeia A and is located located only 12 milliarcseconds (2.5 pc projected) from the strongest source seen in 2002. Milliarcsecond radio imaging is the only technique that could have detected this supernova, since it is embedded within an 80 mJy VLA source and buried in gas and dust (Av 15-25 mag). We suggest that both the new supernova and its nearest neighbor are occurring within a super star cluster, perhaps a newly formed globular cluster akin to those seen in a number of nearby galaxies and particularly galaxy mergers. If so, we are observing this cluster just as its massive stars have begun to explode into a very dense surrounding medium. The likelihood that most supernovae in such a medium will be radio-loud implies that future VLBI imaging over a number of years could lead to a direct measurement of the supernova rate in the Source A starburst, placing powerful constraints on models of present-day star formation processes.

Neff, Susan↗
NASA NTRS1984

The remarkable infrared galaxy Arp 220 = IC 4553

IRAS observations of the peculiar galaxy Arp 220 = IC 4553 show that it is extremely luminous in the far-infrared, with a total luminosity of 2 x 10 to the 12th solar luminosities. The infrared-to-blue luminosity ratio of this galaxy is about 80, which is the largest value of the ratio for galaxies in the UGC catalog, and places it in the range of the 'unidentified' infrared sources recently reported by Houck et al. in the IRAS all-sky survey. Other observations of Arp 220, combined with the luminosity in the infrared, allow either a Seyfert-like or starburst origin for this luminosity.

Soifer, B. T.↗
NASA NTRS1987

The Arp Ring: Galactic or extragalactic?

The Arp Ring is a faint, loop-like structure around the northern end of M81 which becomes apparent only on deep optical photographs of the galaxy. The nature of the Ring and its proximity to M81 are uncertain. Is it simply foreground structure, part of this galaxy, or is it within the M81 system? Infrared Astronomy Satellite (IRAS) maps of the region show a far-infrared counterpart of the Ring. The infrared data are compared with previous optical and radio observations to try to ascertain its physical nature. The poor correlation found between the common infrared/optical structure and the distribution of extragalactic neutral hydrogen, and the fact that its infrared properties are indistinguishable from those of nearby galactic cirrus, imply that the Arp Ring is simply a ring structure in the galactic cirrus.

Abolins, J. A.↗
NASA NTRS1987

Interferometric CO observations of the ultraluminous IRAS galaxies ARP 220, IC 694/NGC 3690, NGC 6420 and NGC 7469

High resolution CO observations of the IRAS galaxies Arp 220, IC 694/NGC 3690, NGC 6240 and NGC 7469 were made with the Millimeter Wave Interferometer of the Owen Valley Radio Observatory. These yield spatial information on scales of 1 to 5 kpc and allow the separation of compact condensations from the more extended emission in the galaxies. In the case of the obviously interacting system IC 694/NGC 3690 the contributions of each component can be discerned. For that galaxy, and also for Arp 220, the unusually high lumonisities may be produced by nonthermal processes rather than by intense bursts of star formation.

Sargent, A. I.↗
NASA NTRS1986

The far-infrared and optical structure of Arp 220

The spatial structure of the luminous peculiar galaxy Arp 220 has been investigated in the far infrared. The results reveal that most of the luminosity is from a source less than 3 kpc in extent, located in the nuclear region of the galaxy. The size constraints yield a lower limit of 0.05 for the 100 micron optical depth, implying a hydrogen column density over 5 x 10 to the 22nd/sq cm. New optical images confirm that the double-lobed optical appearance results from strong absorption across the true nucleus. Arp 220 exhibits three primary features which provide strong evidence for an external source of energy: (1) a chaotic and highly asymmetric galactic halo; (2) a large internal velocity dispersion in CO and H I; and (3) extreme compression of gas and dust. These features are natural consequences of previously proposed models which invoke a direct galactic collision and merger, and are unlikely to result from a long-range tidal interaction with the neighboring galaxy IC 4554.

Joy, M.↗
NASA NTRS1988

A test of the massive binary black hole hypothesis - Arp 102B

The emission-line spectra of several AGN have broad peaks which are significantly displaced in velocity with respect to the host galaxy. An interpretation of this effect in terms of orbital motion of a binary black hole predicts periods of a few centuries. It is pointed out here that recent measurements of the masses and sizes of many low-luminosity AGN imply orbital periods much shorter than this. In particular, it is found that the elliptical galaxy Arp 102B is the most likely candidate for observation of radial velocity variations; its period is expected to be about 3 yr. The H-alpha line profile of Arp 102B has been measured for 5 yr without detecting any change in velocity, and it is thus found that a rather restrictive observational test of the massive binary black hole hypothesis already exists, albeit for this one object.

Helpern, J. P.↗
NASA NTRS1989

The far-infrared structure of the luminous interacting galaxy Arp 299

The strongly interacting galaxies NGC 3690 and IC 694 (or Arp 299) exhibit extensive star formation, a large infrared luminosity, and possible nuclear activity. To determine the origin of the infrared luminosity in this system, high-resolution far-infrared profiles have been obtained in which two distinct sources can clearly be discerned; these observations reveal that 60 percent of the far-infrared luminosity comes from an unresolved source in the center of IC 694, with the remaining 40 percent originating in a compact source in NGC 3690. A new high-resolution 20-micron image of the Arp 299 system is compared with the far-infrared profiles, revealing that NGC 3690 is substantially hotter than IC 694 in the thermal infrared; the observed temperature gradient is opposite to that which is expected if the putative active nucleus in IC 694 generates a significant fraction of the total luminosity.

Joy, Marshall↗
NASA NTRS1989

Kinematic evidence for a relativistic Keplerian disk - Arp 102B

Line profiles were calculated for a Keplerian disk with allowance made for relativistic effects. Excellent agreement was found between the resulting double peaked asymmetric profiles and the H-alpha line of Arp 102B; this yielded an accurate determination of several disk parameters. It is believed that the line profile of Arp 102B shows the most convincing direct kinematic evidence for rotation in any AGN.

Chen, Kaiyou↗
NASA NTRS1989

Structure of line-emitting accretion disks in active galactic nuclei - Arp 102B

The prime objects of the present self-consistent model of a line-emitting accretion disk able to account for the properties observed in a small class of AGNs are Arp 102B and 3C 390.3, whose double-peaked emission lines have been attributed to a Keplerian disk. Improved calculations of the line profile of a relativistic Keplerian disk, generalized to include a variety of emissivity laws as well as local broadening due to electron scattering or turbulence, are noted to fit Arp 102B; analytic and numerical calculations of the solid angle presented by the outer thin disk to an extended isotropic source of illumination demonstrate that the energy budget requirements for line emission from the disk are also satisfied.

Chen, Kaiyou↗
NASA NTRS1991

The discovery of a long H I plume near the peculiar galaxy NGC 2782 (ARP 215)

The peculiar starburst galaxy NGC 2782 (Arp 215) is mapped in the 21-cm H I line using the VLA, and a massive H I plume extending about 5 arcmin toward the northwest is discovered which contains 1.4 x 10 to the 9th solar mass of atomic hydrogen (about 40 percent of the total H I mass of the system). There is also a shorter H I structure extending toward the east, which contains 6.6 x 10 to the 8th solar mass of H I. In the Arp Atlas photograph, NGC 2782 has a disturbed body with bright arcs, possibly ripples, throughout the disk, and a pronounced stellar tail extending 2.7 arcmin toward the east. The eastern H I structure is associated with the beginning of this stellar tail. PDS scanning of the Palomar plates in the vicinity of NGC 2782 reveals a low surface-brightness counterpart to the long HI plume in the northwest. The most likely formation scenario for NGC 2782 is a merger, possibly of unequal mass galaxies, where at least one of the galaxies is gas rich.

Smith, Beverly J.↗
NASA NTRS1992

Mid-infrared imaging of Markarian 231 and Arp 220

High angular resolution observations of Arp 220 and Mrk 231 provide images of the nuclei and show that the source of the strong mid-IR emission is confined to regions less than about 0.5 arcsec or 400 pc in diameter in Mrk 231 and less than 1.5 arcsec x 0.9 arcsec or 320 x 530 pc in Arp 220. If much of the far-IR emission also derives from such a small region, the implied radiation densities are quite high, equivalent to one O star per cu pc. Although in normal galaxies the near-IR traces an older population of evolved, cool stars, such high radiation densities in the IR bright galaxies suggest the possibility that the spatial correlation observed between the near-IR, mid-IR, and radio may hold because emission in all three bands is associated with hot interstellar gas and dust.

Keto, Eric↗