Engineering topics

Harvey, P. M.

Publications and source records attributed to Harvey, P. M..

At least 19 records

NASA NTRS2004

Charting the Winds that Change the Universe, II: The Single Aperture Far Infrared Observatory (SAFIR)

SAFIR will study the birth and evolution of stars and planetary systems so young that they are invisible to optical and near-infrared telescopes such as NGST. Not only does the far-infrared radiation penetrate the obscuring dust clouds that surround these systems, but the protoplanetary disks also emit much of their radiation in the far infrared. Furthermore, the dust reprocesses much of the optical emission from the newly forming stars into this wavelength band. Similarly, the obscured central regions of galaxies, which harbor massive black holes and huge bursts of star formation, can be seen and analyzed in the far infrared. SAFIR will have the sensitivity to see the first dusty galaxies in the universe. For studies of both star-forming regions in our galaxy and dusty galaxies at high redshifts, SAFIR will be essential in tying together information that NGST will obtain on these systems at shorter wavelengths and that ALMA will obtain at longer wavelengths.

Rieke, G. H.↗

NASA NTRS1995

The distribution of far-infrared light in the 'Dusty Hand' galaxy NGC 2146

The Kuiper Airborne Observatory (KAO) has been used to obtain high spatial resolution 50 and 100 micrometers observations of the peculiar galaxy NGC 2146. We find that the far-infrared luminosity of NGC 2146 arises in a 21 arcsecs x less than or = 16 arcsecs (1.5 kpc x less than or equal 1.1 kpc) region (FWHM) elongated along the major axis. This limit is consistent with the size of the central radio continuum and (12)CO (1-0) sources. The far-infrared distribution is slightly more compact than that of the H-alpha; this difference is consistent with observed pattern of extinction in this galaxy. From a study of the energetics in this galaxy, we conclude that young massive stars are largely responsible for powering the far-infrared luminosity of NGC 2146. The far-infrared and CO (1-0) distributions differ from the reddening morphology as seen in optical images and in the Br-gamma/H-alpha ratio. The starlight and the ionized gas appear most highly reddened at the prominent dust lane 15 arcsecs to the west of the nucleus, while the CO and far-infrared emission peak near the nucleus. This result dust lane lies in front of the main body of the galaxy.

Smith, Beverly J.↗

NASA NTRS1995

Far-infrared thermal emission from the inner cooling flow region of NGC 1275

Measurements of the spatial distribution of 100 micrometers emission are presented for NGC 1275, the central galaxy in the Perseus cluster. The emission is clearly resolved on a kiloparsec level, and has the same flux density as seen by IRAS at an epoch when the nonthermal emission was a factor of 10 higher. This emission which traces the greater part of the luminosity of this galaxy, is thus identified as thermal emission from dust. The emission appears to be distributed more nearly like the low-velocity H-alpha filaments in the core of this galaxy than the starlight, extended nonthermal radio, X-ray emission, or high velocity gas. While the dust might be heated by a star-formation region that is fed by the cooling flow in this cluster, the intracluster gas also appears to be energetically capable of this as well, in which case the dust would be, at least at the present time, the dominant cooling mechanism for the hot gas. The large quantity of dust in NGC 1275 is unlikely to have been created within the galaxy, or in the cooling flow, but was probably accreted from a recent galactic interloper.

Lester, D. F.↗

NASA NTRS1994

High-resolution far-infrared observations of the Ring Nebula

High spatial resolution 50 and 100 micron observations of the Ring Nebula reveal a far-infrared emission peak close to the center of the nebula where atomic and molecular emission is at a minimum. Dust in this central peak emission region is heated by direct absorption of radiation from the central star. While the dust temperature in the central peak region is about 50 K (dust emissivity index of 1.5), the temperature of the bulk of the dust located in the regions of the ionized nebular core and the neutral molecular gas is on average lower than 50 K. Ly(alpha) photons are sufficient for heating the dust grains within the nebular core. Far-infrared emission is also found from grains mixed with the molecular gas outside the main ionized nebular core.

Zhang, C. Y.↗

NASA NTRS1994

Far-infrared emission from the bulges of early-type spirals: KAO observations of NGC 4736 (M94) and NGC 3627 (M66)

We present new high spatial resolution Kuiper Airborne Observatory (KAO) 50 and 100 micrometers measurements of the ringed Sab galaxy NGC 4736 and the Sb galaxy NGC 3627. We detect strong far-infrared emission (approximately 10(exp 9) solar luminosity) from the bulge areas of these galaxies, regions where there is little observed star formation. This far-infrared radiation is extended over the bulge with spatial distributions similar to that of the old stellar population. The ratio of far-infrared to H-alpha luminosity for these central sources is significantly larger than for the star-forming regions in these galaxies. This ratio is higher than can be accounted for by dust heating due to a population of young stars with a mass distribution similar to the Salpeter initial mass function assuming current estimates of extinction, unless the upper mass limit is unusually low (approximately B1 stars). On the other hand, the bolometric luminosity of the observed bulge stars is sufficient to account for the far-infrared radiation. Thus, older stars are likely to be important in heating dust in these bulges. The dust in the centers of these galaxies is quite warm, approximately 40 K (lambda(exp -1) emissivity), however, the interstellar radiation fields derived from the optical luminosities are consistent with these temperatures without invoking hidden central star formation or a dusty active galactic nucleus.

Smith, Beverly J.↗

NASA NTRS1994

Infrared Speckle Interferometry with 2-D Arrays

We describe results from a program of speckle interferometry with two-dimensional infrared array detectors. Analysis of observations of eta Carinae made with 58 x 62 InSb detector are discussed. The data have been analyzed with both the Labeyrie autocorrelation, a deconvolution of shift-and-add data, and a phase restoration process. Development of a new camera based on a much lower noise HgCdTe detector will lead to a significant improvement i limiting magnitude for IR speckle interferometry.

Harvey, P. M.↗

NASA NTRS1992

High angular resolution far-infrared observations of Sagittarius B2

High-angular-resolution FIR observations of the continuum emission from the Sagittarius B2 molecular cloud core are reported. Evidence is found for a significantly spatially extended component of the FIR emission at 50- and 100-micron wavelength, which has an angular extent of 1 x 2 arcmin. Its approximate spatial coincidence with a low-level extended component of the radio free-free emission and with the portion of the SGR B2 core having densities not less than 10 exp 5 cu cm derived from molecular observations suggests that the ionizing radiation from the massive stars in the compact sources is diffusing through a region with a beam-averaged visual extinction not less than a few hundred mag. It is inferred that the gas and the dust in the central portion of the cloud surrounding the compact radio free-free/FIR sources are highly clumped.

Goldsmith, Paul F.↗

NASA NTRS1992

NGC 4314. I - Visible and short-wavelength infrared surface photometry of the nucleus and bar

BVI (TI CCD) and JHK (University of Texas IR Camera) surface photometry of NGC 4314, an SB (rs)ap anemic spiral with a nuclear ring containing recent star formation, is presented. The shortwave IR (SWIR) frames reveal a nuclear bar of length 2 arcsec at PA of 0 deg. The nuclear ring and associated dust were detected in all SWIR color indices. A nuclear spiral was detected in the visible and SWIR just exterior to the ring. Extremely low-amplitude spiral-shaped deficits were found in the stellar distribution in the SWIR in this same region. These are attributed to dust, since CO is detectable at or near these locations. Average minor-axis profiles show this galaxy to have a nuclear bulge obeying the de Vaucouleurs r exp 1/4 law for values in the range 2-7 arcsec. The extinction and scattering characteristics of dust near the sites of recent star formation in the nuclear ring are discussed.

Benedict, G. F.↗

NASA NTRS1992

The luminosity of the Galactic center

High signal-to-noise 50- and 90-micron continuum maps of the central 5 x 4 arcmin of the Galaxy made from observations on the Kuiper Airborne Observatory are presented. Dust and luminosity distribution models which are consistent with the data are presented. These data are consistent with a flared disk of dust, centered on the position of Sgr A*, having a central cavity wth a radius of 1 pc. Strong evidence is found for a large amount of dust between the northern and eastern ionized arms located within the cavity. It is argued that this 'tongue' of dust is optically thick at UV and visible wavelengths. Both smooth and clumped dust distributions, consistent with the disk and central cavity, are considered. For the smooth distribution, the dust heating is found to be consistent with the data only for a central UV source of a few x 10 exp 6 solar luminosities.

Davidson, J. A.↗

NASA NTRS1991

The far-infrared morphology of the double-ringed galaxy NGC 4736 (M94) - A ring surrounding an extended nucleus

High spatial resolution 100-micron observations of the central region of the double-ringed spiral galaxy NGC 4736 (M94) were obtained using the Kuiper Airborne Observatory. The data show a strong central peak with secondary peaks at the radius of the inner ring (50 arcsec = 1.6 kpc). The nuclear emission is extended at 100 microns, with a radius of 15 arcsec (500 pc). The far-infrared morphology is similar to that of the molecular gas, while the H I distribution shows a pronounced central depression. Since most of the hydrogen gas in the inner regions of NGC 4736 is in molecular form, it is concluded that the far-infrared emission from NGC 4736 arises mainly from dust associated with molecular gas. The H-alpha distribution differs dramatically from the far-infrared and molecular gas distributions. The ring dominates the H-alpha emission, while the total 100-micron ring emission is only slightly larger than that of the nucleus, yielding an L(FIR)/L(H-alpha) for the nucleus about 100 times that of the ring. The bolometric luminosity of the stars in the inner 1 kpc of NGC 4736 is sufficient to power the far-infrared from this region, which suggests that a significant fraction of the far-infrared emission in the nuclear region of NGC 4736 is powered by non-OB stars rather than by star formation.

Smith, Beverly J.↗

NASA NTRS1991

An infrared jet in Centaurus A - A link to the extranuclear activity in distant radio galaxies?

High-resolution NIR images of the visually obscured central region of Centaurus A (NGC 5128) were obtained with the University of Texas array camera on the AAT in June 1988, in order to investigate the effect of the active nucleus on the surrounding galaxy. The J (1.25 micron), H (1.65 micron), and K (2.2 micron) images of the central 40 arcsec of the galaxy revealed an emission feature extending about 10 arcsec northeast of the nucleus at the same position angle as the X-ray and radio jets. This jet is most prominent at the 1.25 micron wavelength, where its brightness was comparable to that of the nucleus. The observed properties of the 'infrared jet' were found to be similar to those seen in distant radio sources.

Joy, Marshall↗

NASA NTRS1990

High spatial resolution mapping of the Cepheus A region at 20, 50, and 100 microns

The Cepheus A region at 20 microns has been mapped, and a bright, unresolved central source with a peak flux of 41 Jy into a 4.0 arcsec x 4.3 arcsec beam has been detected. One-dimensional slit scans have been obtained in two perpendicular directions across Cepheus A at 50 and 100 microns using a high spatial-resolution sampling technique. The temperature and optical depth profile of the far-IR emission are determined, and a peak temperature of 46 K and peak 100 micron optical depth of 0.4 are derived. Maximum entropy deconvolution of the far-IR scans indicate that there is a bright central core with clumpy extended emission. Within errors the position of the 50/100 micron peak is the same as the 20-micron source; this is interpreted as indicating that the 20 micron radiation represents the short-wavelength emission from the core of the dust cloud seen in the far-IR. It is concluded that an embedded source provides the major source of luminosity in the Cepheus A region.

Ellis, H. B., Jr.↗

NASA NTRS1990

High spatial resolution 100 micron observations of the M83 bar

A program of high spatial resolution far-infrared observations of galaxies using the Kuiper Airborne Observatory (KAO), was conducted to better understand the role of star formation, the general interstellar radiation field, and non-thermal activity in powering the prodigious far-infrared luminosities seen in spiral and interacting galaxies. Here, researchers present observations of the central region of the well-known barred spiral M83 (NGC 5236). The resultant channel 3 scans for M83 and IRC + 10216, after co-addition and smoothing, are shown. These data show that M83 is extended at 100 microns compared to a point source. A simple Gaussian deconvolution of the M83 data with the point source profile from IRC+10216 gives a full width half maximum (FWHM) of about 19 seconds for M83. By comparison with IRC+10216, researchers obtain a flux for the unresolved component in M83 of about 110 Jy. This is about 1/6 the total flux for M83 (Rice et al. 1988) and about 1/2 the PSC flux. The M83 and IRC+10216 profiles in the cross-scan direction (SE-NW) were also compared, and show that M83 is extended in this direction as well, with a width of about 18 seconds. A comparison of the different channel profiles for M83 and IRC+10216 shows that there is an asymmetry in the M83 data, in that the maximum in the profiles shifts from southeast to northwest as channel number increases. This corresponds to the extension in the bar seen in the CO data. Thus the far-infrared emission in the central region of M83 tends to trace the CO bar. The new 100 micron data is also compared with previous H alpha observations from the literature, to determine how well the far-infrared traces the stellar structure, the star formation as measured by H alpha, and the optical colors.

Smith, B. J.↗

NASA NTRS1990

An infrared jet in Centaurus A (NGC 5128): Evidence for interaction between the active nucleus and the interstellar medium

In the present study, higher resolution near infrared images of the visually-obscured central region of Centaurus A were obtained in order to investigate the effects of the active nucleus on the surrounding galaxy. Researchers present J(1.25 microns), H(1.65 microns), and K(2.2 microns) images of the central 40 seconds of the galaxy, taken with the Univ. of Texas InSb array camera on the Anglo Australian 3.9 meter telescope. These images reveal a jet extending approx. 10 arcseconds to the northeast of the nucleus at the same position angle as the x ray and radio jets. The infrared jet is most prominent at the shortest wavelength (1.25 microns), where its brightness surpasses that of the nucleus. The blue appearance of the infrared jet is remarkable considering the heavy obscuration that is evident at visual wavelengths. The amount of reddening in the vicinity of the jet is determined from the measured colors of the stellar core of the galaxy, and this value is used to generate an extinction-corrected energy distribution. In contrast to previously studied optical and infrared jets in active nuclei, the short-wavelength prominence of the Cen A jet indicates that it cannot be attributed to synchrotron emission from a beam of relativistic electrons. The remaining viable mechanisms involve an interaction between the interstellar medium and the active nucleus: the infrared radiation from the jet may be due to emission from interstellar gas that has been entrained and heated by the flow of relativistic particles from the nucleus; alternatively, luminous blue stars may have been created by compression of interstellar material by the relativistic plasma. To investigate these proposed mechanisms, near-infrared spectroscopic studies of Cen A are in progress to look for collisionally excited molecular hydrogen emission lines and recombination lines from ionized gas.

Joy, Marshall↗

NASA NTRS1990

High spatial resolution studies of galaxies in the far IR: Observations with the KAO, and the promise of SOFIA

NASA, in collaboration with the West German Science Ministry (BMFT), plans a larger airborne telescope as a successor to the Kuipper Airborne Observatory (KAO) that will achieve these goals. The Stratospheric Observatory for Infrared Astronomy (SOFIA) is entering the final stages of Phase B review with targeted new start early in the next decade. SOFIA is a 2.7 m diameter telescope that is carried in a Boeing 747SP. In addition to having 3 times the spatial resolution of the KAO, and 10 times the light gathering power, it will incorporate improvements over the KAO in lower optical emissivity and better telescope tracking stability. The thin primary mirror will equilibrate quickly to ambient temperature at an altitude which, accompanied by airflow improvements across the telescope cavity, will result in better image quality. The sensitivity of SOFIA will allow us to see a large number of typical bright galactic HII regions in local group galaxies. The spatial resolution of 8 seconds (full width half maximum Airy disk) at 100 microns will allow these regions to be measured independently, if they are distributed similarly to those in our own galaxy. At this spatial resolution, the disks of normal galaxies will be easily resolved out to distances of several hundred Mpc. This portion of space includes many of the superluminous galaxies discovered by the Infrared Astronomy Satellite (IRAS), and this spatial scale is relevant for studies of the morphology of regions of interaction among the majority of these galaxies that are members of colliding pairs.

Lester, Dan F.↗

NASA NTRS1990

Observations of 40-70 micron bands of ice in IRAS 09371 + 1212 and other stars

IRAS 09371 + 1212 is still an absolutely unique object. This M giant star, with circumstellar CO and a spectacular bipolar nebula, displays unique IRAS FIR colors which had been attributed to strong emission in the 40-70-micron bands of ice, as subsequently supported by the observation of a strong 3.1-micron absorption band. The results of the KAO observations have confirmed its unusual nature: the far-infrared bands of ice are by far the strongest known. Its dust temperature, 50 K or less, is by far the lowest known for a late-type circumstellar envelope.

Omont, A.↗

NASA NTRS1989

The compact far infrared emission from the young stellar object IRAS 16293-2422

High resolution far IR observations at 50 and 100 microns were made of the young stellar object (YSO), IRAS 16293-2422. The observations are part of a systematic high resolution study of nearby YSO's. The purpose is to obtain resolution in the far IR comparable to that at other wavelengths. Until recently, the high resolution that has been available in the far IR has been from either IRAS (angular resolution of approx 4 min) or the KAO using standard FIR photometry (approx 35 sec). With scanning techniques, it is possible to obtain 10 sec resolution on bright sources. Such a resolution is necessary to better determine the physical conditions of the YSO, and to compare with model of star formation. In order to better constrain the models for the source, the YSO was observed at both 50 and 100 microns on several flights in 1988 April from the KAO. Estimates are presented of the size both along the major and minor axis of the disk, as well as estimates of the dust temperature and 100 micron opacity for the YSO.

Butner, Harold M.↗

NASA NTRS1989

High spatial resolution far-infrared scans of W3(OH)

The strong far-infrared continuum source associated with the OH maser-ultracompact H II region W3(OH) was observed from the Kuiper Airborne Observatory in order to determine its size at 50 and 100 microns. Maximum entropy deconvolutions of the slit scans made in orthogonal directions across the source show it to be approximately circular with FWHM sizes of 8 arcsec and 13 arcsec at 50 and 100 microns, respectively. For these sizes, W3(OH) is optically thick in the far-infrared. A spherically symmetric, dusty molecular cloud model is developed to fit the data.

Campbell, M. F.↗