Engineering topics

Poglitsch, A.

Publications and source records attributed to Poglitsch, A..

At least 19 records

NASA NTRS2013

Fast Molecular Outflows in Luminous Galaxy Mergers: Evidence for Quasar Feedback from Herschel

We report the results from a systematic search for molecular (OH 119 micron) outflows with Herschel/PACS in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7 micron silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than−50 km/s, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (approx. 145 deg.) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km/s is seen in only four objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of approx. −1000 km/s are measured in several objects, but median outflow velocities are typically approx.−200 km/s−1. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large active galactic nucleus (AGN) fractions and luminosities [log (L(sub AGN)/L(sub solar)) => 11.8 +/- 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. However, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.

Outfows↗

NASA NTRS2005

Submillimeter Spectroscopy with SOFIA

Four submillimeter spectrometers are being developed for use on SOFIA, the Stratospheric Observatory for Infrared Astronomy. They will be nearly diffraction limited by SOFIA'S 2.5 m telescope, giving for example images of 8.5 arc seconds FWHM at 100 microns. The instruments are FlFI LS, an integral-field imaging grating spectrometer (MPE) covering 40-210 microns with ~150 km/s resolution; SAFIRE an imaging Fabry-Perot spectrometer covering 100-'650 microns with resolution ~200 km/s, and two heterodyne receivers with resolving powers up to ~0.03 km/s: GREAT covering bands from 158-187 um, 110-125, and 62-65 microns, and CASIMIR, operating from 150-264 and 508-588 microns. These instruments will enable a variety of studies including topics relating to the origins of stars, planets, and biogenic materials in the interstallar medium of our own and other galaxies. Opportunities for observing with these and the other SOFIA instruments will be available to general investigators. SOFIA is a joint project of NASA in the U.S. and DLR in Germany.

Erickson, E.↗

NASA NTRS1997

Gas and Dust Properties in Dwarf Irregular Galaxies

We present a study of the 158 (micron)meter [C II] fine structure emission line from a sample of 11 low metallicity irregular galaxies using the NASA Kuiper Airborne Observatory (KAO). Our preliminary results demonstrate that the ratio of the 158 (micron)meter [C II] emission to the CO-12(1 yields 0) emission ranges from 6,000 to 46,000. These ratios are significantly enhanced relative to clouds within the Galaxy and to normal metallicity galaxies, which typically have values in the range 2,000 to 6,300. We also find that the [C II] emission in dwarf irregular galaxies can be up to 5% of the far-infrared (FIR) emission, a higher fraction of the FIR than in normal metallicity galaxies. We discuss these results for the dwarf irregular galaxies and compare them to those observed in normal metallicity galaxies. The enhanced 158 (micron)meter [C II] emission relative to CO-12(1 yields 0) emission can be understood in terms of the increased penetration depth of ultraviolet (UV) photons into the clouds in low metallicity environments.

Jones, A. P.↗

NASA NTRS1994

Ultraviolet-illuminated molecular cloud boundaries: Extended (C II) 158 micron emission toward L1630

We have made a large-scale map of the 158 micrometers C(+) line toward the L1630/Orion B molecular cloud. The map covers a approximately 35 min x 45 min area which includes the NGC 2024 H II region, zeta Ori, the reflection nebula NGC 2023, and the Horsehead nebula. Emission in the (C II) line is very widespread. The line was detected at levels in excess of a few 10(exp -4) ergs/sq cm/s/sr over almost the entire mapped region. Extended emission associated with the NGC 2024 H II region and its envelope accounts for more than half of the (C II) flux. Over this approximately 1.5 x 2.5 pc region, the amount of gas-phase carbon in the form of C(+) is comparable to the amount of carbon in CO. This result, together with the (C II) distribution, implies that (C II) emission arises on the surfaces of clumps throughout the cloud rather than in a single layer at the H II region boundary. Away from the H II region, most of the (C II) emission comes from the western edge of the L1630 cloud and probably results from excitation by external OB stars. The overall extent of the (C II) emission is comparable to that of millimeter molecular lines, but the distributions are different in detail. The difference in (C II) and molecular line distributions, in particular, the larger extent of the (C II) emission west of NGC 2024 implies large variations in the radio of the (C II) and CO J = 1 goes to 0 intensities. Models of photon-dominated regions can explain the relation between (C II) and CO intensities only if one considers the cloud edges and cloud interior separately. We propose a method for using (C II) and radio continuum emission to characterize the relationship between OB stars and photon-dominated regions.

Jaffe, D. T.↗

NASA NTRS1994

Ultraviolet illuminated molecular cloud boundaries: Extended (C II) 158 micrometer emission toward L1630

The construction of a large scale map of the 158 micrometer C+ line toward the L1630/Orion B molecular cloud, covering an approximately 35' by 45' area which includes the NGC 2024 H II region, zeta-Ori, the reflection nebula NGC 2023, and the Horsehead nebula, is reported. Emission in the C II line is very widespread. The line was detected at levels in excess of a few 0.0001 erg/sq cm/s/sr over almost the entire mapped region. Extended emission associated with the NGC 2024 H II region and its envelope accounts for more than half of the C II flux. Over this approximately 1.5 by 2.5 pc region, the amount of gas phase carbon in the form of C+ is comparable to the amount of carbon in CO. This result, together with the C II distribution implies that C II emission arises on the surface of clumps throughout the cloud rather than in a single layer at the H II region boundary. Away from the H II region, most of the C II emission comes from the western edge of the L1630 cloud and probably results from excitation by external OB stars. The overall extent of the C II emission is comparable to that of millimeter molecular lines but the distributions are different in detail. The difference in C II and molecular line distributions, in particular, the larger extent of the C II emission west of NGC 2024 implies large variations in the ratio of the C II and J = 1 towards 0 intensities. Models of photon dominated regions can explain the relation between C II and CO intensities only if the cloud edges and cloud interior are considered separately. A method for using C II and radio continuum emission to characterize the relationship between OB stars and photon dominated regions is proposed.

Jaffe, D. T.↗

NASA NTRS1993

The (C2) 158 micrometer emission from the Horsehead nebula

The C II 158 micrometer line and the several rotational lines of CO, CO-13, and CS toward selected positions in the Horsehead extinction region in IC 434 are mapped. The observations show that the region has a gas density of about 10,000 cu cm and an external UV (Ultraviolet) flux to 20 to 100 times the average interstellar UV field. Although this is a regime where the C+ emission varies rapidly with UV intensity, fine structure line emission from gas with this range of physical conditions were not investigated previously. Comparisons of results with models of photodissociation regions show that existing plane parallel photodissociation region models are in general agreement with the observed intensity. It is not necessary to invoke a clumpy structure in the boundary layer to explain the observations, but the overall geometry of the cloud is important in determining the distribution of C+ emission.

Zhou, S.↗

NASA NTRS1993

158 micron forbidden C II mapping of NGC 6946 - Probing the atomic medium

A well-sampled map (23 x 17 kpc) of the strong 158 micron forbidden C II cooling line in the Scd galaxy NGC 6946 at 55 arcsec resolution is presented which was taken with the MPE/UCB Far-infrared Imaging Fabry-Perot Interferometer (FIFI) in the Kuiper Airborne Observatory. It is concluded that the line emission in NGC 6946 is present in three spatially distinct components including nucleus, spiral arms, and extended region. An extended emission region is a source of most of the forbidden C II luminosity in NGC 6946. The 1 arcmin nuclear component has a line luminosity of 1.5 x 10 exp 7 solar luminosity and contributes 0.15 percent of the galaxy's total FIR luminosity. An extended component of forbidden C II emission is found to exist past the molecular extent of the galaxy and to be present to at least the full dimensions of the map. This component is attributed to a mixture of neutral and atomic clouds.

Madden, S. C.↗

NASA NTRS1993

158 micron forbidden C II mapping of the Orion molecular cloud

A fully sampled, 1000-point, 1-arcmin-resolution map of the inner 6.5 x 10 arcmin (alpha x delta) regions of the Orion Nebula in the 157.7409-micron forbidden fine-structure line is constructed. Large-scale strip maps in forbidden C II across the face of the Orion molecular cloud, and CO(17-16), (14-13), and (7-6) spectra are obtained at selected positions in the Orion H II region/molecular cloud interface. Strong forbidden C II line emission is observed across the face of the Orion molecular. The total forbidden C II luminosity from the Orion molecular cloud is about 1500 solar luminosities, or 0.3 percent of the FIR luminosity. The extended forbidden C II emission probably arises in either the UV-exposed surface of the molecular cloud or from the surfaces of UV-exposed clumps within the molecular cloud.

Stacey, G. J.↗

NASA NTRS1993

The 158 micron (CII) mapping of galaxies: Probing the atomic medium

Using the MPE/UCB Far-infrared Imaging Fabry-Perot Interferometer (FIFI) on the Kuiper Airborne Observatory (KAO), we have made large scale maps of (CII) in the spiral galaxies NGC 6946, NGC 891, M83 and the peculiar elliptical Cen A, thus allowing for the first time, detailed studies of the spatial distribution of the FIR line emission in external galaxies. We find that the (CII) emission comes from a mixture of components of interstellar gas. The brightest emission is associated with the nuclear regions, a second component traces the spiral arms as seen in the nearly face on spiral galaxies NGC 6946 and M83 and the largest star forming/H2 regions contained within them, and another extended component of low brightness can be detected in all of the galaxies far from the nucleus, beyond the extent of CO emission.

Madden, S. C.↗

NASA NTRS1993

Far-infrared line images of dwarf galaxies

Irregular dwarf galaxies are about ten times more widespread in the universe than regular spiral galaxies. They are characterized by a relatively low metallicity, i.e., lower abundance of the heavier elements (metals) with respect to hydrogen than in the solar neighborhood. These heavier elements in the form of molecules, atoms, or ions, which have radiative transitions in the infrared play a decisive role in the energy balance of the ISM and thereby for the formation of stars. Dwarf galaxies are thus model cases for the physical conditions in the early phase of the universe. Large Magellanic Cloud: 30 Doradus. The two nearest dwarf galaxies are the Magellanic clouds at a distance approximately 50 kpc. The LMC contains 30 Dor, a region with young, extremely massive stars which strongly interact with the surrounding ISM on account of their stellar winds and intense UV radiation. 30 Dor is the brightest object in the LMC at almost all wavelengths.

Poglitsch, A.↗

NASA NTRS1993

Neutral gas in the central 2 parsecs of the Galaxy

New spectroscopic observations are presented that elucidate the spatial distribution, kinematics, and density structure of atomic and molecular gas within about 2 p from IRS 16/SgrA*. The measurements confirm the presence of a dense clumpy molecular gas ring surrounding a short-lived central cavity of much lower mean gas density. It appears that this ring consists of several distinct and probably short-lived gas streamers that result from accretion from the massive molecular clouds within 10-30 pc of the center toward the central gravitational potential. Within 1 pc of SgrA* a large atomic cloud is found that appears to be falling in from more than 3 pc Galactocentric distance into the central cavity. The northern and eastern 'arms' of ionized gas are very likely dense bright rims at the surface of this atomic cloud that is now exposed to the intense UV radiation from the few central arcsec surrounding IRS 16/SgrA*.

Jackson, J. M.↗

NASA NTRS1992

Stressed and unstressed Ge:Ga detector arrays for airborne astronomy

The construction and operation of 2D arrays of both unstressed and stressed Ge:Ga photoconductive detectors for far-IR astronomy from the Kuiper Airborne Observatory is presented. The 25 element (5 x 5) arrays are designed for a new cryogenically cooled spectrometer. The 2D spatial array described has the advantage of absolute registry between pixels in a map.

Stacey, G. J.↗

NASA NTRS1992

158 micrometers (CII) mapping of NGC 6946: Probing the atomic medium

The strong 158 micrometers (C2) cooling line of the NGC 6946 galaxy is investigated. The data was acquired with a far infrared imaging Fabry-Perot interferometer with 55 minutes resolution. About 1 percent of the total far infrared luminosity of the galaxy is analyzed. The (C2) emission comes from a mizture of components of interstellar gas. The brightest emission is associated with the nucleus, a second component traces the spiral arms and the largest star forming/H2 regions contained within them, and a third extended component of low brightness can be detected at least 12 kpc from the nucleus. The nuclear and spiral arm components are most likely associated with dense photon dominated regions at molecular cloud surfaces that are exposed to ultraviolet radiation produced by young massive stars. The (C2) emission is analyzed and the cooling rate in the atomic medium is consistent with photoelectric heating by diffuse ultraviolet radiation.

Madden, S. C.↗

NASA NTRS1992

158 micrometers (CII) mapping of the Orion molecular cloud

Data from the inner regions of the Orion nebula in the 157.7409 micrometers (CII) fine structure line is investigated. Large scale strip maps in (CII) across the face of the Orion molecular cloud, and CO spectra at selected positions in the Orion HII region/molecular cloud interface were obtained. The total (CII) luminosity from the Orion molecular cloud is estimated to be approximately 1500 of the solar luminosity or 0.3 of the far infrared luminosity. The overall properties of the Orion molecular cloud deduced are: the photodissociated gas to molecular gas mass fraction, the (CII) line to far infrared continuum intensity ratio and the (CII)/CO(12) (1 to 0) line intensity ratio are the same for the Orion molecular cloud and the nuclei of non-starburst galaxies. The observations provide an important link between (CII) emission from galactic molecular clouds and the nuclei of external galaxies.

Stacey, G. J.↗

NASA NTRS1991

The optical depth of the 158 micron forbidden C-12 II line - Detection of the F = 1 - 0 forbidden C-13 II hyperfine-structure component

The detection of the F = 1 - 0 hyperfine component of the 158-micron forbidden C-13 II fine-structure line in the interstellar medium is reported. A 12-point intensity map was obtained of the forbidden C-13 distribution over the inner 190-arcsec (R.A.) X 190-arcsec (decl.) regions of the Orion Nebula using an imaging Fabry-Perot interferometer. The forbidden C-12 II/C-13 II line intensity ratio varies significantly over the region mapped. It is highest (86 +/-0) in the core of the Orion H II region, and significantly lower (62 +/-7) in the outer regions of the map, reflecting higher optical depth in the forbidden C-12 II line here. It is suggested that this enhanced optical depth is the result of limb brightening of the optically thin forbidden C-13 II line at the edges of the bowl-shaped H II region blister.

Stacey, G. J.↗

NASA NTRS1991

The optical depth of the 158 micrometer (C-12 II) line: Detection of the F=1 yields 0 (C-13 III) hyperfine-structure component

The first detection of the F = 1 yields 0 hyperfine component of the 158 micrometer (C-13 II) fine structure line in the interstellar medium is reported. A twelve point intensity map was obtained of the (C-13 II) distribution over the inner 190 inch (right ascension) by 190 inch (declination) regions of the Orion nebula using an imaging Fabry-Perot interferometer. The (C-12 II)/(C-13 II) line intensity ratio varied significantly over the region mapped. It is highest (86 plus or minus 9) in the core of the Orion H II region and significantly lower (62 plus or minus 7) in the outer regions of the map, reflecting higher optical depth in the (C-12 II) line here. It is suggested that this enhanced optical depth is the result of limb brightening of the optically thin (C-13 II) line at the edges of the bowl-shaped H II region blister. If the C-12/C-13 abundance ratio is 43, the (C-12 II) line in the inner regions of the Orion nebula, has a low optical depth: tau sub 12 approximately = 0.75 plus or minus 0.25. The optical depth together with the large brightness temperature of the (C-12 II) line (approximately 160 K) requires that the excitation temperature of the P-2 sub 3/2 level be approximately 310 K, in very good agreement with the previous analysis of the physical conditions of the Orion interface region based on fine structure line intensity ratios and photodissociation region models. If the C-12/C-13 abundance ratio is 67, the line optical depth is somewhat larger (tau sub 12 approximately = 1.85), and the transition excitation temperature is somewhat smaller (approximately 190 K) than that predicted by these models. The present results therefore support values approximately = 43 for the C-12/C-13 abundance ratio in the Orion nebula.

Stacey, G. J.↗

NASA NTRS1991

The MPE/UCB far-infrared imaging Fabry-Perot interferometer (FIFI)

FIFI, an imaging spectrometer with two or three Fabry-Perot interferometers in a series for astronomical observations in the FIR range, is described. Spectral resolutions of 2 km/s can be obtained with FIFI. Design considerations are discussed as well as optics, the detector array, the transimpedance amplifier array, signal demodulation, data acquisition, and instrument control.

Poglitsch, A.↗

NASA NTRS1991

A survey of the 158 micron forbidden C II fine-structure line in the central 50 parsecs of the Galaxy

NASA's Kuiper Airborne Observatory has been used to conduct an extensive, velocity-resolved survey at 1-arcsec resolution of the 158-micron forbidden C II fine-structure line emission in the central 50 pc of the Galaxy. The emission is found to be strongest toward the rotating circumnuclear disk surrounding Sgr A West; a continuous bridge of the emission connects the Sgr A complex to the thermal radio filaments in the radio arc 10 arcmin north of the center. This suggests a direct physical connection. The brightest emission occurs preferentially near the edges of the massive Galactic center molecular clouds. It is concluded that these clouds are predominantly ionized by external UV photons.

Poglitsch, A.↗