共查询到20条相似文献,搜索用时 46 毫秒
1.
J. E. Wink W. J. Altenhoff J. Bieging B. Butler H. Butner C.G.T. Haslam E. Kreysa R. Martin R. Mauersberger J. McMullin D. Muders W. Peters J. Schmidt J. B. Schraml A. Sievers P. Stumpff A. Von Kapp-Herr C. Thum R. Zylka 《Earth, Moon, and Planets》1997,77(3):165
The concept of simultaneous multifrequency continuum observations, successfully tested on Comet Hyakutake, was applied to
Comet Hale-Bopp, using the Heinrich Hertz Submillimeter Telescope (HHT) with the four color bolometer between 250 and 870
GHz, the IRAM 30m telescope at 240 Ghz, the MPIfR 100-m telescope at 32 GHz, and the IRAM interferometer near 90 and 240 GHz.
Near-simultaneous measurements were done between February 15 and April 26, 1997, mainly concentrated in mid March shortly
before perigee of the comet.
The measurements gave the following preliminary results:
Interferometer detection of the nuclear thermal emission. If the signal at the longest interferometer spacing of 170 mis due
to thermal emission from the nucleus only, its equivalent diameter is ∼49 km. If, however, this signal contains a contribution
from a strongly centrally peaked halo distribution(e.g., r−2 density variation) the diameter may be as low as 35 km. The emission found interferometrically was always 5″ north and 0.1
sec east from the position predicted by Yeoman's solution 55.The comparison of the interferometric continuum emission with
the simultanously obtained molecular line observations (reported on this conference) shows the origin of the strongest line
emission concentrated on the nucleus. The 30-m observations show a radio halo with a gaussian FWHP of ∼11, corresponding to
a diameter of 11000 km at geocentric distance of 1.2 a.u.
A spectral index of ∼3.0 for the total signal, which may indicate a smaller mean particle size than for Hyakutake. Assuming
an average cometary density of 0.5 gcm−3, the mass contained in the nucleus is ∼1$#x2013;3 1019 g and 1012 g in the particle halo.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
S. García-Burillo F. Combes J. Graciá-Carpio A. Usero M. Guélin 《Astrophysics and Space Science》2008,313(1-3):261-265
High-resolution CO maps are an essential tool to search for observational evidence of AGN fueling in galaxy nuclei. While
their capabilities will be surpassed by ALMA, current mm-interferometers can already provide relevant information on scales
which are critical for the process of angular momentum transfer in fueling the AGN. In this context we present the latest
results issued from the NUclei of GAlaxies (NUGA) project, a high-resolution (0.5′′–1′′) CO survey of low luminosity AGNs conducted with the IRAM Plateau de Bure interferometer (PdBI). The use of more specific
molecular tracers of dense gas can probe the feedback influence of activity on the chemistry and energy balance in the interstellar
medium of nearby galaxies, a prerequisite to understanding how feedback operate at higher redshift galaxies. We discuss the
results obtained in an ongoing study devoted to probe the feedback of activity from nearby Seyferts to high-redshift QSO. 相似文献
3.
Tetsuo Hasegawa Takaaki Arai Nobuyuki Yamaguchi Fumio Sato 《Astrophysics and Space Science》2008,313(1-3):91-94
We report mapping observations of a 35 pc × 35 pc region covering the Sgr B2 molecular cloud complex in the 13CO (3-2) and the CS (7-6) lines using the ASTE 10 m telescope with high angular resolution. The central region was mapped
also in the C18O (3-2) line. The images not only reproduce the characteristic structures noted in the preceding millimeter observations,
but also highlight the interface of the molecular clouds with a large velocity jump of a few tens of km s−1. These new results further support the scenario that a cloud–cloud collision has triggered the formation of massive cloud
cores, which form massive stars of Sgr B2. Prospects of exciting science enabled by ALMA are discussed in relation to these
observations. 相似文献
4.
The results of morphological and spectral study of the galaxies Kaz 5, Kaz 92, and Kaz 390 are presented. The observations
were made on the 2.6-m telescope at the Byurakan Observatory with the VAGR microlenses spectrograph. Isophotes of the images
of the galaxies are constructed in the Hα, [NII] λλ6584 , 6548, and [SII] λλ6731, 6717 emission lines and in the continuum. The masses of Kaz 5 and Kaz 92 are determined to be 8.6 × 108 M⊙ and 6.1 × 109 M⊙ , respectively. The mass of the gaseous component in the centers of regions I and IV of Kaz 390, which encompass a 1 pixel
area, are also determined. The morphological structure of the central region of Kaz 5 in the observed spectral range, λλ6400–6800?, differs completely from the structure of the same part of the galaxy observed with the 6-m and 2.5-m telescopes. It is shown
that these differences in the structure in images of Kaz 5 are mostly explained by the comparatively low resolution of the
telescope in combination with the VAGR spectrograph. Absorbing matter also contributes to this effect. It is also shown that
a “deficit” of nitrogen has been observed in the region of Kaz 390 studied here (a circle of diameter 40″).
Translated from Astrofizika, Vol. 52, No. 1, pp. 63–74 (February 2009). 相似文献
5.
A. Chalabaev E. Le Coarer P. Rabou Y. Magnard P. Petmezakis D. Le Mignant 《Experimental Astronomy》2002,14(3):147-181
The GraF instrument using a Fabry-Perot interferometer cross-dispersed with a grating was one of the first integral-field
and long-slit spectrographs built for and used with an adaptive optics system. We describe its concept, design, optimal observational
procedures and the measured performances. The instrument was used in 1997–2001 at the ESO3.6 m telescope equipped with ADONIS
adaptive optics and SHARPII+camera. The operating spectral range was 1.2–2.5 μm. We used the spectral resolution from 500
to 10 000 combined with the angular resolution of 0.1″–0.2″. The quality of GraF data is illustrated by the integral field
spectroscopy of the complex0.9″ × 0.9″ central region of η Car in the1.7 μm spectral range at the limit of spectral and angular
resolutions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
M. Stupar M. D. Filipović Q. A. Parker G. L. White T. G. Pannuti P. A. Jones 《Astrophysics and Space Science》2007,307(4):423-435
The Parkes–MIT–NRAO (PMN) radio survey has been used to generate a quasi all-sky study of Galactic Supernova Remnants (SNRs)
at a common frequency of 4.85 GHz (λ=6 cm). We present flux densities estimated for the sample of 110 Southern Galactic SNRs (up to δ=−65°) observed with the Parkes 64-m radio telescope and an additional sample of 54 from the Northern PMN (up to δ=+64°) survey undertaken with the Green Bank 43-m (20 SNRs) and 91-m (34 SNRs) radio telescopes. Out of this total sample
of 164 selected SNRs (representing 71% of the currently 231 known SNRs in the Green catalogue) we consider 138 to provide
reliable estimates of flux density and surface brightness distribution. This sub-sample represents those SNRs which fall within
carefully chosen selection criteria which minimises the effects of the known problems in establishing reliable fluxes from
the PMN survey data. Our selection criteria are based on a judicious restriction of source angular size and telescope beam
together with careful evaluation of fluxes on a case by case basis. Direct comparison of our new fluxes with independent literature
values gives excellent overall agreement. This gives confidence in the newly derived PMN fluxes when the selection criteria
are respected. We find a sharp drop off in the flux densities for Galactic SNRs beyond 4 Jy and then a fairly flat distribution
from 5 to 9 Jy, a slight decline and a further flat distribution from 9 to 20 Jy though the numbers of SNR in each Jy bin
are low. We also re-visit the contentious Σ–D (radio surface brightness–SNRs diameter) relation to determine a new power law index for a sub-sample of shell type SNRs
which yields β=−2.2±0.6. This new evaluation of the Σ–D relation, applied to the restricted sample, provides new distance estimates and their Galactic scale height distribution.
We find a peak in the SNR distribution between 7–11 kpc with most restricted to ±100 pc Galactic scale height. 相似文献
7.
Thomas Bertram Andreas Eckart Melanie Krips Johannes Staguhn 《Astrophysics and Space Science》2005,295(1-2):303-308
We present the results of 12CO(1-0) and 12CO(2-1) observations on UGC 1347 obtained with BIMA and the IRAM 30 m telescope. UGC 1347 is a member of the Abell 262 cluster. In Abell 262, a nearby spiral rich cluster, the signs of galaxy interaction and therefore the mechanisms which play an important role in galaxy evolution within clusters can be studied with high spatial resolution. Aside from its bright central region, UGC 1347 features a second prominent source at the southern tip of the bar, which has been identified as region with recent enhanced star formation. The CO observations prove the existence of reservoirs of cold molecular gas at the positions of both bright regions. 相似文献
8.
Chuan Peng Zhang Jarken Esimbek Jian Jun Zhou Gang Wu Zhi Mao Du 《Astrophysics and Space Science》2012,337(1):283-302
There are relatively few H2CO mappings of large-area giant molecular cloud (GMCs). H2CO absorption lines are good tracers for low-temperature molecular clouds towards star formation regions. Thus, the aim of
the study was to identify H2CO distributions in ambient molecular clouds. We investigated morphologic relations among 6-cm continuum brightness temperature
(CBT) data and H2CO (111−110; Nanshan 25-m radio telescope), 12CO (1–0; 1.2-m CfA telescope) and midcourse space experiment (MSX) data, and considered the impact of background components
on foreground clouds. We report simultaneous 6-cm H2CO absorption lines and H110α radio recombination line observations and give several large-area mappings at 4.8 GHz toward W49 (50′×50′), W3 (70′×90′),
DR21/W75 (60′×90′) and NGC2024/NGC2023 (50′×100′) GMCs. By superimposing H2CO and 12CO contours onto the MSX color map, we can compare correlations. The resolution for H2CO, 12CO and MSX data was ∼10′, ∼8′ and ∼18.3″, respectively. Comparison of H2CO and 12CO contours, 8.28-μm MSX colorscale and CBT data revealed great morphological correlation in the large area, although there
are some discrepancies between 12CO and H2CO peaks in small areas. The NGC2024/NGC2023 GMC is a large area of HII regions with a high CBT, but a H2CO cloud to the north is possible against the cosmic microwave background. A statistical diagram shows that 85.21% of H2CO absorption lines are distributed in the intensity range from −1.0 to 0 Jy and the ΔV range from 1.206 to 5 km s−1. 相似文献
9.
Javier Alcolea Valentín Bujarrabal Roberto Neri 《Astrophysics and Space Science》2008,313(1-3):235-239
M 1–92 is a very well studied bipolar pPN that can be considered an archetype of this type of sources; it shows a clear axial
symmetry, along with the kinematics characteristic of this class of envelopes around post-AGB stars. We performed sub-arcsecond
resolution observations of the J=2–1 rotational line of 13CO in M 1–92 with the new extended configurations of the IRAM Plateau de Bure interferometer, for studying the morphology
and velocity field of the molecular gas better in the nebula, particularly in its central parts. We found that the equatorial
structure dividing the two lobes is a thin flat disk, which expands radially with a velocity proportional to the distance
to the central stellar system. The kinetic age of this equatorial flow is very similar to that measured in the two lobes,
suggesting that the whole structure was formed as a result of a single event some 1200 yr ago, after which the nebula reached
an expansion velocity field with axial symmetry. The small widths and velocity dispersion in the gas forming the lobe walls
confirm that the acceleration responsible for the nebular shape could not last more than 100–120 yr. In view of the similarity
to η Car, we speculate on the possibility that the whole nebula was formed as a result of a magneto-rotational explosion in a
common-envelope system. The study of the possible importance of this mechanism in the context of global PNe and pPNe reshaping
should be one on the fields in which future ALMA observations will make a crucial contribution.
Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG
(Germany) and IGN (Spain). 相似文献
10.
Jill M. Rathborne James M. Jackson Robert Simon Qizhou Zhang 《Astrophysics and Space Science》2009,324(2-4):155-162
Infrared dark clouds (IRDCs) are cold, dense molecular clouds identified as extinction features against the bright mid-infrared Galactic background. Our recent 1.2 mm continuum emission survey of IRDCs reveals many compact (<0.5 pc) and massive (10–2100 M⊙) cores within them. These prestellar cores hold the key to understanding IRDCs and their role in star formation. Here, we present high angular resolution spectral-line and mm/sub-mm continuum images obtained with the IRAM Plateau de Bure Interferometer and the Sub-Millimeter Array towards three high-mass IRDC cores. The high angular resolution images reveal that two of the cores are resolved into multiple, compact protostellar condensations, while the remaining core contains a single, compact protostellar condensation with a very rich molecular spectrum, indicating that it is a hot molecular core. The derived gas masses for these condensations suggest that each core is forming at least one high-mass protostar, while two of the cores are also forming lower-mass protostars. The close proximity of multiple protostars of disparate mass indicates that these IRDCs are in the earliest evolutionary states in the formation of stellar clusters. 相似文献
11.
V. L. Karbovs’ky P. F. Lazorenko V. N. Andruk V. V. Kleshchenok M. O. Litvin K. O. Bogatyrev E. V. Denisyuk 《Kinematics and Physics of Celestial Bodies》2011,27(4):204-210
Specifications of a new Apogee Alta U47 CCD camera mounted at the Kyiv meridian axial circle (MAC) are presented. The camera
is based on the 1024 × 1024 pxl e2v CCD47-10 with pixel sizes of 13 × 13 μm. Observations are carried out in the scan-drift
mode with an effective exposure time of 77 s for equatorial stars. The MAC photometric system answers the standard Johnson
V band, the MAC limiting magnitude V is 17
m
. The test MAC observations of 2009 give positional accuracy and V magnitude errors equal to approximately 0.1″ and 0.09
m
, respectively, for Tycho-2 stars. The telescope is used for observations of equatorial stars with the purpose of detecting
their positions, proper motion, and brightness. 相似文献
12.
R. A. Burenin M. G. Revnivtsev I. M. Khamitov I. F. Bikmaev A. S. Nosov M. N. Pavlinsky R. A. Sunyaev 《Astronomy Letters》2011,37(2):100-112
We study the variability of the optical flux from the peculiar Galactic source SS 433 based on observations with the Russian-Turkish
1.5-m telescope. We describe in detail the technique of highquality photometric measurements with a time resolution of 0.3–1
s using an ordinary CCD. Through test observations of nonvariable stars, we show that atmospheric turbulence introduces no
significant distortions into the light curves. Therefore, such data are well suited for studying the aperiodic variability of various objects. 相似文献
13.
We present observations of four filaments that exhibit large-amplitude periodic mass motion. Observations are obtained using
the high resolution (2″) and high cadence (1 min) Hα telescope system at the Big Bear Solar Observatory (BBSO). The motions
found in these events are along the axis of the filaments, and are associated with the activity of a nearby flare or filament.
The most characteristic properties of these motions are long period (≥ q80 min), large distance (≥ q 4 × 104 km) of mass transport at much higher velocity (≥ q 30 km s−1) than ever detected from filament motions. The velocity, period, dimension and damping timescale measured for these motions
are presented, and discussed to identify the most plausible restoring force and damping mechanism. 相似文献
14.
Y. M. Pihlstrm J. E. Conway R. S. Booth P. J. Diamond B. Koribalski 《New Astronomy Reviews》1999,43(8-10)
We report on observations, with sub-parsec resolution, of neutral hydrogen seen in absorption in the λ=21 cm line against the nucleus of the active spiral galaxy NGC 5793. The absorption line consists of three components separated in both location as well as velocity. We derive HI column densities of 2×1022 cm−2 assuming a gas spin temperature of 100 K. For the first time we are able to reliably estimate the HI cloud sizes (≈15 pc) and atomic gas densities (≈200 cm−3). Our results suggest that the HI gas is not associated with the <10 pc region which presumably contains the H2O masers, but it is more distant from the nucleus, and is probably associated with the r1 kpc gas seen in CO. 相似文献
15.
Massimo Tarenghi 《Astrophysics and Space Science》2008,313(1-3):1-7
The Atacama Large Millimeter/Submillimeter Array (ALMA) is an international millimeter-wavelength radio telescope under construction
in the Atacama Desert of northern Chile. ALMA will be situated on a high-altitude site at 5000 m elevation which provides
excellent atmospheric transmission over the instrument wavelength range of 0.3 to 3 mm. ALMA will be comprised of two key
observing components—a main array of up to sixty-four 12-m diameter antennas arranged in a multiple configurations ranging
in size from 0.15 to ∼18 km, and a set of four 12-m and twelve 7-m antennas operating in a compact array ∼50 m in diameter
(known as the Atacama Compact Array, or ACA), providing both interferometric and total-power astronomical information. High-sensitivity
dual-polarization 8 GHz-bandwidth spectral-line and continuum measurements between all antennas will be available from two
flexible digital correlators.
At the shortest planned wavelength and largest configuration, the angular resolution of ALMA will be 0.005″. The instrument
will use superconducting (SIS) mixers to provide the lowest possible receiver noise contribution, and special-purpose water
vapor radiometers to assist in calibration of atmospheric phase distortions. A complex optical fiber network will transmit
the digitized astronomical signals from the antennas to the correlators in the Array Operations Site Technical Building, and
post-correlation to the lower-altitude Operations Support Facility where the array will be controlled, and initial construction
and maintenance of the instrument will occur. ALMA Regional Centers in the US, Europe, Japan and Chile will provide the scientific
portals for the use of ALMA; early science observations are expected in 2010, with full operations in 2012. 相似文献
16.
The “circumpolar survey” technique allowed us to achieve a rather high antenna temperature sensitivity of 0.5 mK at 6 cm on
a fixed antenna with a relatively narrow frequency resolution band (600 kHz) and an angular resolution of 45″ × 7′. Starting
from 2007 we use a Fourier spectral analyzer with a survey band 10 times broader than that of previous observations. This
upgrade allowed us to rapidly perform repeated test observations, which confirmed the power-law nature and the frequency structure
of spatial spectra in two strips in the vicinity of the celestial pole in the 4′–16′ interval of angular periods. These observations
also showed that the Galactic CH molecular line that was by chance captured in our survey strip (Λ-doubling of rotational
transition) has nothing to do with the emission spectra we obtained. The angular pattern of emission in two main lines of
Λ-doubling (4847.84 and 4870.12 MHz) is absolutely different, whereas there is practically no maser amplification in the CH
line to explain this fact. Our observations also confirm the H110 α line (4874.157 MHz), which forms in the tenuous ionized Galactic hydrogen at such relatively high latitudes. Other features
of the spatial spectra also appear to be quite real, although their interpretation remains unclear and requires further studies. 相似文献
17.
Claudia Comito Peter Schilke Ulrike Endesfelder Izaskun Jiménez-Serra Jesus Martín-Pintado 《Astrophysics and Space Science》2008,313(1-3):59-63
The direct detection of accretion onto massive protostars through rotating disks constitutes an important tile in the massive-star-formation-theory
mosaic. This task is however observationally very challenging. A very interesting example is Cepheus A HW2. The properties
of the molecular emission around this YSO seems to suggest the presence of a massive rotating disk (cf. Patel et al. in Nature
437:109, 2005). We have carried out sub-arcsec-resolution PdBI observations of high-density and shock tracers such as SO2, SiO, CH3CN, and CH3OH towards the center of the outflow. A detailed analysis of the spatial distribution and of the velocity field traced by
all observed species leads us to conclude that, on a ∼700 AU scale, the Cep-A “disk” is actually the result of the superposition
of multiple hot-core-type objects, at least one of them ejecting an outflow at a small angle with respect to the line of sight.
Together with the well-known large-scale outflow ejected by HW2, this setup makes for a very complex spatial and kinematic
picture.
Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG
(Germany) and IGN (Spain). 相似文献
18.
C. L. Brogan T. R. Hunter R. Indebetouw C. J. Chandler Y. L. Shirley R. Rao A. P. Sarma 《Astrophysics and Space Science》2008,313(1-3):53-57
We describe results from recent Submillimeter Array observations of massive protostellar objects (CepheusA-East, NGC7538 IRS1,
and G5.89-0.39) with resolutions ranging from 0.8″ to 2″. A wide range of spectral and continuum properties are observed,
with one unifying theme: at these resolutions all of the studied sources reveal multiple submillimeter cores. Some are observed
to have cm-wavelength counterparts, and others not, suggesting a range of evolutionary stages coexisting in close proximity.
In the presence of such complexity and multiplicity of sources, these data suggest that the interpretation of diagnostics
such as kinematic velocity gradients and temperatures that are strongly dependent on spatial resolution should be approached
cautiously. 相似文献
19.
We present the observations of the Irr galaxy IC 10 at the 6-m SAO telescope with the panoramic Multi-Pupil Fiber Spectrograph
(MPFS). Based on the results of these observations and our long-slit spectroscopy performed previously, we have investigated
the ionized-gas emission spectrum in the region of intense star formation and refined the gas metallicity estimates. We show
that the “diagnostic diagrams” constructed from our observations agree best with the new improved ionization models by Martin-Manjon
et al. Using these models, we have determined the electron density and gas ionization parameter and ionizing-cluster characteristics,
the age and mass, from the spectra of the investigated HII regions. The cluster ages and masses are shown to be within the
ranges 2.5–5 Myr and (0.2–1) × 105
M
⊗, respectively. 相似文献
20.
Melanie Krips Andreas Eckart Roberto Neri Joerg-Uwe Pott Jens Zuther Julia Scharwächter Thomas Bertram 《Astrophysics and Space Science》2005,295(1-2):95-100
We present new interferometric observations of the molecular gas distribution and kinematics in the nuclei of different active galaxies at high angular resolution and high sensitivity carried out with the IRAM Plateau de Bure interferometer (PdBI). The observations cover galaxies in a redshift range of 0.03–1.4. We have so far observed five different active galaxies: NGC3718, NGC1068, HE1029–1831, 3C48 and Q0957+561. The first two objects belong to the NUGA (NUclei of GAlaxies) project – an international collaboration mainly between Spain, France and Germany – containing about 30 Seyfert and LINER galaxies. Both are at the same distance of 14Mpc and show a warped gas and dust disk. The new mosaic map of NGC3718 corrected for short-spacing effects with IRAM 30 m observations well demonstrates the existence of the warped gas disk with several secondary maxima in the projected gas distribution caused by orbit crowding effects. Based on these new data we have improved recent simulations of the warped disk in NGC3718. HE1029–1831 and 3C48 are nearby QSOs. HE1029–1831 is taken out of the Cologne nearby QSO sample. The maps of the integrated CO(1–0) and CO(2–1) emission clearly show that the molecular gas is mostly related to the central bulge with a non-negligible fraction distributed along the bar known from optical observations. Our new CO data of 3C48 unveil new information about the kinematics of its molecular gas complementing and improving further studies based on previous infrared observations and detailed multi-particle simulations. Finally, new measurements of the CO(1–0) line in Q0957+561 – a highly-red-shifted, gravitationally lensed quasar – will be presented as a link to earlier evolutionary stages of active galaxies and their hosts. 相似文献