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At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

On the origin of extinction in the Coma cluster of galaxies

Visual extinction of distant clusters seen through the Coma cluster seem to suggest that dust may be present in the hot x ray emitting intracluster gas. However, the Infrared Astronomy Satellite (IRAS) failed to detect any infrared emission from the cluster at the level expected from the extinction measurements. Researchers carried out a detailed analysis of the properties of intracluster dust in the context of a model which includes continuous injection of dust by the cluster galaxies, grain destruction by sputtering, and transient grain heating by the hot plasma. Computed infrared fluxes are in agreement with the upper limit obtained from the IRAS. The calculations, and the constraint implied by the IRAS observations, suggest that the intracluster dust must be significantly depleted compared to interstellar abundances. Researchers discuss possible explanations for the discrepancy between the observed visual extinction and the IRAS upper limit.

Rephaeli, Y.↗
NASA NTRS1984

IRAS observations of NGC 1052

The galaxy NGC 1052 has been observed with the IRAS satellite. The infrared emission at 100 microns is substantially larger than a smooth extrapolation of the radio data. Because of the large diaphragm size of IRAS, it is impossible to decide uniquely if the infrared radiation represents a self-absorbed nonthermal spectrum or thermal reradiation by heated dust.

Neugebauer, G.↗
NASA NTRS1986

Moderate resolution spectroscopy for the Space Infrared Telescope Facility (SIRTF)

A conceptual design for an IR spectrometer capable of both low resolution (lambda/Delta-lambda = 50; 2.5-200 microns) and moderate resolution (1000; 4-200 microns) has been developed. This instrument will allow the spectroscopic study in the infrared of objects ranging from within the solar system to distant galaxies. The spectroscopic capability provided by this instrument for SIRTF will give astronomical orders of magnitude greater sensitivity for the investigation of faint objects than has been previously available.

Houck, J. R.↗
NASA NTRS2015

Predicting the Redshift 2 H-Alpha Luminosity Function Using [OIII] Emission Line Galaxies

Upcoming space-based surveys such as Euclid and WFIRST-AFTA plan to measure Baryonic Acoustic Oscillations (BAOs) in order to study dark energy. These surveys will use IR slitless grism spectroscopy to measure redshifts of a large number of galaxies over a significant redshift range. In this paper, we use the WFC3 Infrared Spectroscopic Parallel Survey (WISP) to estimate the expected number of H-alpha emitters observable by these future surveys. WISP is an ongoing Hubble Space Telescope slitless spectroscopic survey, covering the 0.8 - 1.65 micrometers wavelength range and allowing the detection of H-alpha emitters up to z approximately equal to 1.5 and [OIII] emitters to z approximately equal to 2.3. We derive the H-alpha-[OIII] bivariate line luminosity function for WISP galaxies at z approximately equal to 1 using a maximum likelihood estimator that properly accounts for uncertainties in line luminosity measurement, and demonstrate how it can be used to derive the H-alpha luminosity function from exclusively fitting [OIII] data. Using the z approximately equal to 2 [OIII] line luminosity function, and assuming that the relation between H-alpha and [OIII] luminosity does not change significantly over the redshift range, we predict the H-alpha number counts at z approximately equal to 2 - the upper end of the redshift range of interest for the future surveys. For the redshift range 0.7 less than z less than 2, we expect approximately 3000 galaxies per sq deg for a flux limit of 3 x 10(exp −16) ergs per sec per sq cm (the proposed depth of Euclid galaxy redshift survey) and approximately 20,000 galaxies per sq deg for a flux limit of approximately 10(exp −16) ergs per sec per sq cm (the baseline depth of WFIRST galaxy redshift survey).

Redshift↗
NASA NTRS1979

Far-infrared observations of H 2 regions and associated galactic and extragalactic sources

Using imaging techniques maps were made at 50 and 100 micrometers with one foot resolution of a region around the galactic center about one-half degree in extent. Higher resolution maps were made of the central portion of the galaxy at 30, 50, and 100 micrometers. Resolution maps of a reflection nebula were also made. Infrared sources associated with molecular clouds were investigated.

Source record↗
DOE OSTI2020

Radial Star Formation Histories in 32 Nearby Galaxies

The spatially resolved star formation histories are studied for 32 normal star-forming galaxies drawn from the Spitzer Extended Disk Galaxy Exploration Science survey. At surface brightness sensitivities fainter than 28 mag arcsec{sup −2}, the new optical photometry is deep enough to complement archival ultraviolet and infrared imaging and to explore the properties of the emission well beyond the traditional optical extents of these nearby galaxies. Fits to the spectral energy distributions using a delayed star formation history model indicate a subtle but interesting average radial trend for the spiral galaxies: the inner stellar systems decrease in age with increasing radius, consistent with inside-out disk formation, but the trend reverses in the outermost regions with the stellar age nearly as old as the innermost stars. These results suggest an old stellar outer disk population formed through radial migration and/or the cumulative history of minor mergers and accretions of satellite dwarf galaxies. The subset of S0 galaxies studied here show the opposite trend compared to what is inferred for spirals: characteristic stellar ages that are increasingly older with radius for the inner portions of the galaxies, and increasingly younger stellar ages for the outer portions. This result suggests that either S0 galaxies are not well modeled by a delayed-τ model, and/or that S0 galaxies have a more complicated formation history than spiral galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1995

High angular resolution 30 microns observations of the Galactic Center

We have mapped the central 2 min (5 pc) of the Galaxy with 4 sec resolution at 30 microns, using the MSFC bolometer array on the NASA Infrared Telescope Facility at Mauna Kea. Complementary maps at 10 and 20 microns covering the same region were obtained contemporaneously with the same instrumentation. The maps encompass both the central cavity at the very center of the Galaxy and the disk of gas and dust which surrounds it. Our data show thermal emissions from dust particles within the cavity and - for the first time at this resolution - within the disk itself. The emission peaks at the position of IRS1 at all three wavelengths, and the 20/30 micron brightness ratio falls uniformly from this peak toward the outer regions of the source. The 30 micron emission correlates well with the HCN emission in the southwest portion of the circumnuclear disk and with the (O I) emission in the north. No feature is apparent at the position of SgrA at any of the three wavelengths. The circumnuclear disk was discovered from the KAO and has been extensively studied in both continuum and line emission in numerous subsequent flights. The poster will attempt to show how these latest ground-based observations intersect and build upon these airborne investigations.

Telesco, Charles M.↗
DOE OSTI2023

Star formation and molecular gas properties of post-starburst galaxies

Post-starburst galaxies are believed to be in a rapid transition between major merger starbursts and quiescent ellipticals. Their optical spectrum is dominated by A-type stars, suggesting a starburst that was quenched recently. While optical observations suggest little ongoing star formation, some have been shown to host significant molecular gas reservoirs. This led to the suggestion that gas depletion is not required to end the starburst, and that star formation is suppressed by other processes. We present NOEMA CO(1−0) observations of 15 post-starburst galaxies with emission lines consistent with active galactic nucleus (AGN) photoionization. We collect post-starburst candidates with molecular gas measurements from the literature, with some classified as classical E + A, while others with line ratios consistent with AGN and/or shock ionization. Using far-infrared observations, we show that systems that were reported to host exceptionally large molecular gas reservoirs host in fact obscured star formation, with some systems showing star formation rates comparable to ULIRGs. Among E + A galaxies with molecular gas measurements, 7 out of 26 (26 per cent) host obscured starbursts. Using far-infrared observations, post-starburst candidates show similar SFR– M H 2 and Kennicutt–Schmidt relations to those observed in star-forming and starburst galaxies. In particular, there is no need to hypothesize star formation quenching by processes other than the consumption of molecular gas by star formation. The combination of optical, far-infrared, and CO observations indicates that some regions within these galaxies have been recently quenched, while others are still forming stars in highly obscured regions. All this calls into question the traditional interpretation of such galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
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 NTRS1993

A joint program with Japanese investigators to map carbon 2 line emission from the galaxy

A large portion of the inner galactic plane has been mapped in the far-infrared (C II) line using a balloon-borne survey instrument. Complete coverage is reported from 25 degrees north to 80 degrees south of the galactic center and extending a few degrees on each side of the plane. Effective resolution is 14.1 acrmin (FWHM) and contour levels begin at 2 E -5 ergs/(s x sq. cm x ster). When compared with 100 micron dust emission observed by IRAS the (C II) appears well correlated with the dust emission except for a 10 degree region centered on the galactic center where emission from the gas is much weaker than that from the dust.

Low, Frank J.↗
NASA NTRS2024

The Atacama Cosmology Telescope: Galactic Dust Structure and the Cosmic PAH Background in Cross-correlation with WISE

We present a cross-correlation analysis between 1ʹ resolution total intensity and polarization observations from the Atacama Cosmology Telescope (ACT) at 150 and 220 GHz and 15ʺ mid-infrared photometry from the Wide-field Infrared Survey Explorer (WISE) over 107 12°.5 × 12°.5 patches of sky. We detect a spatially isotropic signal in the WISE×ACT TT cross-power spectrum at 30σ significance that we interpret as the correlation between the cosmic infrared background at ACT frequencies and polycyclic aromatic hydrocarbon (PAH) emission from galaxies in WISE, i.e., the cosmic PAH background. Within the Milky Way, the Galactic dust TT spectra are generally well described by power laws in ℓ over the range 10 3 < ℓ < 10 4 , but there is evidence both for variability in the power-law index and for non-power-law behavior in some regions. We measure a positive correlation between WISE total intensity and ACT E-mode polarization at 1000 < ℓ ≲ 6000 at >3σ in each of 35 distinct ∼100 deg 2 regions of the sky, suggesting that alignment between Galactic density structures and the local magnetic field persists to subparsec physical scales in these regions. The distribution of TE amplitudes in this ℓ range across all 107 regions is biased to positive values, while there is no evidence for such a bias in the TB spectra. This work constitutes the highest-ℓ measurements of the Galactic dust TE spectrum to date and indicates that cross-correlation with high-resolution mid-infrared measurements of dust emission is a promising tool for constraining the spatial statistics of dust emission at millimeter wavelengths.

Rodrigo Córdova Rosado↗
NASA NTRS2011

A CANDELS WFC3 Grism Study of Emission-Line Galaxies at Z approximates 2: A mix of Nuclear Activity and Low-Metallicity Star Formation

We present Hubble Space Telescope Wide Field Camera 3 slitless grism spectroscopy of 28 emission-line galaxies at z approximates 2, in the GOODS-S region of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). The high sensitivity of these grism observations, with > 5-sigma detections of emission lines to f > 2.5 X 10(exp -18( erg/s/ square cm, means that the galaxies in the sample are typically approximately 7 times less massive (median M(star). = 10(exp 9.5)M(solar)) than previously studied z approximates 2 emission-line galaxies. Despite their lower mass, the galaxies have [O-III]/H-Beta ratios which are very similar to previously studied z approximates 2 galaxies and much higher than the typical emission-line ratios of local galaxies. The WFC3 grism allows for unique studies of spatial gradients in emission lines, and we stack the two-dimensional spectra of the galaxies for this purpose. In the stacked data the [O-III] emission line is more spatially concentrated than the H-Beta emission line with 98.1% confidence. We additionally stack the X-ray data (all sources are individually undetected), and find that the average L(sub [O-III])/L(sub 0.5.10keV) ratio is intermediate between typical z approximates 0 obscured active galaxies and star-forming galaxies. Together the compactness of the stacked [O-III] spatial profile and the stacked X-ray data suggest that at least some of these low-mass, low-metallicity galaxies harbor weak active galactic nuclei.

Trump, Jonathan R.↗
NASA NTRS1987

Interstellar processes; Proceedings of the Symposium, Grand Teton National Park, WY, July 1-7, 1986

The conference presents papers on the Milky Way as a galaxy; observations of components of the interstellar medium; interstellar magnetic properties; interstellar processes on a galactic scale; dynamical processes in interstellar clouds; interstellar dust grains; interstellar chemical processes; and heating, cooling, and radiative processes. Attention is given to H2 in the Galaxy, hot interstellar gas in the Galactic disk and halo, interstellar magnetic fields, cloud formation and destruction, theoretical approaches to interstellar turbulence, and infrared absorption and emission characteristics of interstellar PAHs. Other topics include gas phase chemical processes in molecular clouds, the chemical evolution of galaxies, and the atomic and molecular physics of interstellar heating and cooling.

Hollenbach, David J.↗
DOE OSTI2022

Linking Extragalactic Transients and Their Host Galaxy Properties: Transient Sample, Multiwavelength Host Identification, and Database Construction

Understanding the preferences of transient types for host galaxies with certain characteristics is key to studies of transient physics and galaxy evolution, as well as to transient identification and classification in the LSST era. Here we describe a value-added database of extragalactic transients—supernovae, tidal disruption events, gamma-ray bursts, and other rare events—and their host galaxy properties. Based on reported coordinates, redshifts, and host galaxies (if known) of events, we cross-identify their host galaxies or most likely host candidates in various value-added or survey catalogs, and compile the existing photometric, spectroscopic, and derived physical properties of the host galaxies in these catalogs. This new database covers photometric measurements from the far-ultraviolet to mid-infrared. Spectroscopic measurements and derived physical properties are also available for a smaller subset of hosts. For our 36,333 unique events, we have cross-identified 13,753 host galaxies using host names, plus 4480 using host coordinates. Besides those with known hosts, there are 18,100 transients with newly identified host candidates. This large database will allow explorations of the connections of transients to their hosts, including a path toward transient alert filtering and probabilistic classification based on host properties.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1999

Search for Obscured Nucleus in a Luminous IRAS Galaxy NGC 6240

IRAS discovered very luminous objects which emit the vast majority of their radiation in the infrared wavelength. The energy source of such a tremendous amount of emission is not understood. Starburst and active galactic nuclei (AGN) are thought to be the origin of their power. X-ray observations are expected to be able to reveal the characteristics of the AGN component. However, some are very X-ray quiet, because the AGN is thought to be obscured by a large column density. In order to determine the primary luminosity of the nucleus, we need an X-ray observation with a wide energy band at least up to several tens of keV. We propose to observe NGC 6240, one of the luminous IRAS galaxies, to investigate the characteristics of its AGN, which must be obscured by large column density.

Leighly, Karen↗
NASA NTRS2011

The Merger History, AGN and Dwarf Galaxies of Hickson Compact Group 59

Compact group galaxies often appear unaffected by their unusually dense environment. Closer examination can, however, reveal the subtle, cumulative effects of multiple galaxy interactions. Hickson Compact Group (HCG) 59 is an excellent example of this situation. We present a photometric study of this group in the optical (HST), infrared (Spitzer) and X-ray (Chandra) regimes aimed at characterizing the star formation and nuclear activity in its constituent galaxies and intra-group medium. We associate five dwarf galaxies with the group and update the velocity dispersion, leading to an increase in the dynamical mass of the group of up to a factor of 10 (to 2.8 x 10(exp 13) Stellar Mass), and a subsequent revision of its evolutionary stage. Star formation is proceeding at a level consistent with the morphological types of the four main galaxies, of which two are star-forming and the other two quiescent. Unlike in some other compact groups, star-forming complexes across HCG 59 closely follow mass-radius scaling relations typical of nearby galaxies. In contrast, the ancient globular cluster populations in galaxies HCG 59A and B show intriguing irregularities, and two extragalactic HII regions are found just west of B. We age-date a faint stellar stream in the intra-group medium at approx. 1 Gyr to examine recent interactions. We detect a likely low-luminosity AGN in HCG 59A by its approx. 10(exp 40) erg/s X-ray emission; the active nucleus rather than star formation can account for the UV+IR SED. We discuss the implications of our findings in the context of galaxy evolution in dense environments.

Konstantopoulos, I. S.↗
NASA NTRS1999

A Kinematic Link Between Boxy Bulges, Stellar Bars, and Nuclear Activity in NGC 3079 and NGC 4388

We present direct kinematic evidence for bar streaming in two active galaxies with boxy stellar bulges. The Hawaii Imaging Fabry-Perot Interferometer was used on the Canada-France-Hawaii 3.6-m telescope and the University of Hawaii 2.2-m telescope to derive the two-dimensional velocity field of the line-emitting gas in the disks of the Sc galaxy NGC 3079 and the Sb galaxy NGC 4388. In contrast to previous work based on long-slit data, the detection of the bar potential from the Fabry-Perot data does not rely on the existence of inner Lindblad resonances or strong bar-induced shocks. Simple kinematic models which approximate the intrinsic gas orbits as nonintersecting, inclined elliptical annuli that conserve angular momentum characterize the observed velocity fields. In NGC 3079, bar streaming motions with moderately eccentric orbits (e = b/a approx. 0.7) aligned along PA = 130 deg. intrinsic to the disk (PA = 97 deg. on the sky) are detected out to R(sub b) = 3.6 kpc. The orbits become increasingly circular beyond that radius (e = 1 at R(sub d) approx. = 6 kpc). The best model for NGC 4388 includes highly eccentric orbits (e approx. 0.3) for R(sub) less than or equal to 1.5 kpc which are aligned along PA = 135 deg. intrinsic to the disk (PA = 100 deg. on the sky). The observed "spiral arms" are produced by having the orbits become increasingly circular from the ends of the bar to the edge of the disk (R(sub d) approx. = 5 kpc), and the intrinsic bar PA shifting from 135 deg. to 90 deg.. Box-shaped bulges in both NGC 3079 and NGC 4388 are confirmed using new near-infrared images to reduce dust obscuration. Morphological analysis of starlight in these galaxies is combined with the gas kinematics derived from the Fabry-Perot spectra to test evolutionary models of stellar bars that involve transitory boxy bulges, and to quantify the importance of such bars in fueling active nuclei. Our data support the evolutionary bar models, but fail to prove convincingly that the stellar bars in NGC 3079 and NGC 4388 directly trigger or sustain the nuclear activity.

Veilleux, S.↗
DOE OSTI2024

Close Major-merger Pairs at z = 0: Star-forming Galaxies with Pseudobulges

Abstract We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges with Sérsic indexn< 2) in a local close major-merger galaxy pair sample (H-KPAIR). With data from new aperture photometries in the optical and near-infrared bands (aperture size of 7 kpc) and from the literature, we find that the mean Age of central stellar populations in Spirals with pseudobulges is consistent with that of disky galaxies and is nearly constant against the bulge-to-total ratio (B/T). Paired Spirals have a slightly lower fraction of pure disk galaxies (B/T ≤ 0.1) than their counterparts in the control sample. Compared to SFGs with classical bulges, those with pseudobulges have a higher (>2σ) mean of specific star formation rate (sSFR) enhancement (sSFR enh = 0.33 ± 0.07 versus sSFR enh = 0.12 ± 0.06) and broader scatter (by ∼1 dex). The eight SFGs that have the highest sSFR enh in the sample all have pseudobulges. A majority (69%) of paired SFGs with strong enhancement (having sSFR more than 5 times the median of the control galaxies) have pseudobulges. The Spitzer data show that the pseudobulges in these galaxies are tightly linked to nuclear/circum-nuclear starbursts. Pseudobulge SFGs in S+S and in S+E pairs have significantly (>3σ) different sSFR enhancement, with the means of sSFR enh = 0.45 ± 0.08 and −0.04 ± 0.11, respectively. We find a decrease in the sSFR enhancements with the density of the environment for SFGs with pseudobulges. Since a high fraction (5/11) of pseudobulge SFGs in S+E pairs are in rich groups/clusters (local density N 1Mpc ≥ 7), the dense environment might be the cause for their low sSFR enh .

Astronomy & Astrophysics↗