Detection of Anomalous Microwave Emission in the Perseus Molecular Cloud with the COSMOSOMAS Experiment
We present direct evidence for anomalous microwave emission in thePerseus molecular cloud, which shows a clear rising spectrum from 11 to17 GHz in the data from the COSMOSOMAS experiment. By extending thefrequency coverage using W ilkinson Microwave Anisotropy Probe mapsconvolved with the COSMOSOMAS scanning pattern, we reveal a peak fluxdensity of 42+/-4 Jy at 22 GHz integrated over an extended area of 1.65d×1.0d centered on R.A.=55.4d+/-0.1d and decl.=+31.8d+/-0.1d(J2000). The flux density that we measure at this frequency is nearly anorder of magnitude higher than can be explained in terms of normalGalactic emission processes (synchrotron, free-free, and thermal dust).An extended IRAS dust feature, G159.6-18.5, is found near this position,and no bright unresolved source that could be an ultracompact H IIregion or gigahertz-peaked source could be found. An adequate fit forthe spectral density distribution can be achieved from 10 to 50 GHz byincluding a very significant contribution from electric dipole emissionfrom small spinning dust grains.
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Pre-main-sequence stars in the young open cluster NGC 1893. I. A spectroscopic search for candidates in the area photometrically surveyed
We present low-resolution spectroscopy of the majority of the stars inthe field of NGC 1893 which were classified asnon-members based on the photometry of Marco et al. (2001). We separatefield stars from pre-main-sequence members based on a combination ofspectral type and photometric indices which allows us to determine thereddening to the objects. For candidates to pre-main-sequence objects,we present intermediate-resolution spectra. We confirm 3 F-typeemission-line objects as massive T Tauri stars in NGC1893 and find two good candidates for being absorption-lineHerbig A stars. A B5 star is a very good candidate for anabsorption-line Herbig B star. We also investigate the nature ofemission-line B-type stars close to the cluster centre. Availableevidence suggests that both classical Be stars and Herbig Be stars arepresent in NGC 1893. Based on observations obtainedat the Asiago Observatory (Italy), the Isaac Newton Telescope (La Palma,Spain) and Observatoire de Haute Provence (CNRS, France).
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Photometric and Spectroscopic Study of the Young Open Cluster NGC 1893
We present uvbyβ CCD photometry of the field of the open clusterNGC 1893. Our photometry is deep enough to cover the completemain-sequence B spectral type. We identify ~50 very likely members ofthe cluster down to spectral type B9-A0, some of which have much higherreddenings than the average. We derive a color excess E(b-y)=0.33+/-0.03and a dereddened distance modulusV0-MV=13.9+/-0.2. From the β index, weidentify several candidates as emission-line stars, for which we haveobtained spectroscopy. Three of them display spectra corresponding tospectral type F but showing Hα in emission. Photometricmeasurements in this and previous studies indicate strong variability.These characteristics show them to be pre-main-sequence stars ofspectral type F. We also identify two likely Herbig Be stars. Theseresults hint at the existence of a sizable pre-main-sequence populationin NGC 1893.
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1 deg- and 2.5°-scale interferometric surveys in the northern sky at 5GHz
We present observations from a 5-GHz short-baseline interferometer atJodrell Bank, which has been operating at spacings of 0.702 and 1.79mbetween 1990 and 1997. These surveys covered 2 sr of the sky betweenDec.=+30 deg and +55 deg, at rms sensitivities of 10 and 8μK, onangular scales of ~1 deg (l=184+/-15) and ~2.5° (l=71+/-13)respectively. This sensitivity was achieved by using the maximum entropymethod (MEM) to find the most probable underlying sky fluctuations. Wehave used the Green Bank 5-GHz catalogue to model point sourcecontributions, for subtraction from the survey at each spacing. Theresulting rms signal measured at intermediate and high Galacticlatitudes, in directions away from strong extragalactic sources, is50+/-6μK at the shorter spacing and 54+/-3μK at the longerspacing. Allowing for the interferometer window function and acontribution arising from uncorrected point source variability, thesevalues correspond to intrinsic rms levels of 373+/-55 and1080+/-120μK for narrow and wide spacings. We compare these valueswith measurements at 10GHz, and conclude that between these frequenciesthe Galactic spectrum is predominantly synchrotron in nature. Furthercomparison with the Tenerife experiments, sensitive to different angularscales, suggests that the angular power spectrum is flat(l-2) over the observed l-range.
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Near-infrared photometry of the young open clusters NGC 1893 and Berkeley 86
We present photometry in the J and K near-infrared bands for two regionscentered on the young open clusters NGC 1893 and Berkeley 86. We study700 stars down to K = 17 in the field of NGC 1893, and about 2000 starsin the field of Berkeley 86 down to K ~ 16.5, for which near-infraredphotometry was insofar not available. Coupling J-K data with UBVphotometry taken from literature, we produce reddening correctedcolour-magnitude diagrams. We find that our data are consistent withprevious determinations: the clusters are roughly coeval with an agebetween 4 and 6 million years. The mean reddening (measured as E(J-K))values turn out to be 0.35 and 0.50 for NGC 1893 and Berkeley 86,respectively. Using colour-colour plots we discuss the presence ofcandidate pre-main sequence stars showing infrared excess. Candidatesare found in both cluster regions, confirming the young age of theseclusters. Based on observations taken at TIRGO
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Gamma-Ray Pulsars and Massive Stars in the Solar Neighborhood
We revisit the association of unidentified Galactic plane EGRET sourceswith tracers of recent massive star formation and death. Up-to-datecatalogs of OB associations, supernova remnants (SNRs), young pulsars, HII regions, and young open clusters were used in finding counterpartsfor a recent list of EGRET sources. It has been argued for some timethat EGRET source positions are correlated with SNRs and OB associationsas a class; we extend such analyses by finding additional counterpartsand assessing the probability of individual source identifications.Among the several scenarios relating EGRET sources to massive stars, wefocus on young neutron stars as the origin of the gamma -ray emission.The characteristics of the candidate identifications are compared to theknown gamma -ray pulsar sample and to detailed Galactic populationsyntheses using our outer gap pulsar model of gamma -ray emission. Boththe spatial distribution and luminosity function of the candidates arein good agreement with the model predictions; we infer that youngpulsars can account for essentially all of the excess low latitude EGRETsources. We show that with this identification, the gamma -ray pointsources provide an important new window into the history of recentmassive star death in the solar neighborhood.
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The Far-Ultraviolet Imaging Spectrograph Experiment on Spartan-204 /STS-63
The Naval Research Laboratory's Far Ultraviolet Imaging Spectrograph(FUVIS) experiment was flown as the Spartan-204 payload on shuttlemission STS-63, February 3-11, 1995. Its science objectives were tostudy astronomical and artificially-induced sources of diffusefar-ultraviolet radiation. The astronomical sources of interest includediffuse nebulae (H II regions, reflection nebulae, and supernovaremnants) and the diffuse galactic background radiation, formeasurements of temperature and abundances (in the gaseous phase) and ofthe scattering properties of dust grains (particularly at shortwavelengths). The instrument design optimized its diffuse-sourcesensitivity and long-slit imaging capability. Observations were obtainedin the 970-2000 A and 1230-2000 A wavelength ranges, with spectralresolution as good as 5 A. The field of view along the spectrograph slitwas 2.7R and the spatial (imaging) resolution along the slit was about 3arc min. Targets of observation in the STS-63 mission included the OrionNebula (observed with several slit azimuth orientations centered on thenebula), the region of 15 Mon, IC 410, the Crab Nebula, the CaliforniaNebula, and the Rosette Nebula. Processing of the flight film recordings(from the spectrograph and aspect cameras) was in progress at theabstract submission deadline. Quick-look results, and plans fornear-future data reduction and analysis, will be presented at theconference.
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A catalog of bright-rimmed clouds with IRAS point sources: Candidates for star formation by radiation-driven implosion. I - The Northern Hemisphere
Forty-four bright-rimmed clouds associated with IRAS sources have beenselected from the Palomar Sky Survey prints. They are good candidatesfor the sites of star formation induced by radiation-driven implosions;three well-established cases of radiation-driven implosions inbright-rimmed globules have been reported by Sugitani et al. (1989).Nine of the bright-rimmed clouds are known to be associated withmolecular outflows and two (including one with an outflow) with HHobjects. Most of their sizes are not more than 1 pc, similar to those ofBok globules. The luminosities of the associated IRAS sources arerelatively large, about 10 to 10,000 solar luminosities, compared tothose of the IRAS sources associated with dark globules or dense coresin dark cloud complexes. IRAS luminosity to cloud mass ratios aresignificantly greater than those in dark globules or in dense cores ofdark cloud complexes.
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Spectrophotometric Studies of Galactic Nebulae - Part Thirty-One - the Dense Condensations in NGC7635 - IC410 Nebulae and Stars with Wide H Emission Line
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WO ist der Himmel AM buntesten ?
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Catalogue of Eclipsing and Spectroscopic Binary Stars in the Regions of Open Clusters
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Decameter observations of the nebulae IC 405 and IC 410
Results are presented of absorption measurements of the H II regions IC405 and IC 410 obtained at five freequencies between 12.6 and 25 MHzwith 0.5-1.0 deg resolution using the UTR-2 radio telescope. The averagenonthermal radiation density of the interstellar medium at 12.6 MHztoward IC 405 is determined to be 135 K/pc, whereas it is found to be 37K/pc toward IC 410. It is found that the kinetic temperature of IC 410is 11,000 K and that the electron density is approximately 12/cu cm.Calculations are presented for several other physical parameters towardthe center of IC 410: optical depth at 25 MHz = 8, emission measure =8,000 pc/cm exp 6, and mass = 3400 solar masses.
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Catalog of CO radial velocities toward galactic H II regions
This is a catalog of 242 molecular cloud complexes which are associatedwith optical H II regions. CO observations were made toward all but fiveof the H II regions in the Sharpless catalog and toward 62 additionalsuspected H II regions, 33 of which are previously uncataloged. Radialvelocities are tabulated for each molecular cloud complex found to beassociated with an H II region. The CO antenna temperature and linewidth are given for the most intense CO line seen toward each source.The catalog also summarizes previous CO observations as well as theoptical distances to the stars exciting the H II regions. Radio-quiet HII regions (those with 1.4 GHz flux densities less than 100 mJy) arefound to be well correlated with objects having no associated CO. A listof kinematically distinct complexes is tabulated to facilitateinvestigations of the motions of the complexes.
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Photoelectric photometry of diffuse gaseous nebulae in the H-alpha line
Results are given of the H-alpha photometry of diffuse gaseous nebulaeobserved with a nebula photometer attached to the 60-cm reflector of thePic du Midi Observatory. Isophote maps are given for the followingobjects: the Orion nebula, the Rosette nebula, IC 410, IC 434 and NGC2024, and M 8 (NGC 6523); several scans are presented for NGC 6514, NGC7000, and Barnard's Loop. In cases where the spherical modelapproximation may be performed, the variation of electron density withradius was determined; for the Rosette nebula a steeper decrease towardthe center than previously established was found.
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H2O masers near OB associations
Four new water masers have been found in the vicinity of three OBassociations. One of these, in Cep OB3, is among the most intensesources yet discovered and may be related to the most recent epoch ofstar formation in the OB association. Two others, one in CMa OB1, theother in M16, have large radial velocities relative to their associatedmolecular clouds. These results are discussed in the context of starformation and CO line self-reversal within the individual sources.
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The chemical composition of galactic and extragalactic H II regions
Line intensities are compiled for a large number of galactic H IIregions, and physical conditions and chemical abundances are computed.Detailed observations of extragalactic H II regions are examined inorder to deduce the electron temperatures from a measurement of theforbidden N II line at 5755 A and to deduce a more accurate sulfurabundance from the forbidden S III line at 6312 A. The questions ofabundance gradients in the Galaxy and of line intensities as abundanceindicators are considered. Improved abundances are presented for aninner-arm H II region in M101, and abundance gradients across M101 arecompared with those in the Galaxy. The results show that: (1) there areoxygen and nitrogen abundance gradients among H II regions in theGalaxy; (2) certain line ratios exhibit generally the same gradients inthe Galaxy as in other spiral galaxies; and (3) abundance gradients inM101 are similar to those in the Galaxy.
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The chemical composition of galactic and extragalactic H II regions.
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H II regions of the northern Milky Way: medium-large-field photographic atlas and catalogue.
Abstract image available at:http://adsabs.harvard.edu/abs/1976A&AS...25...25D
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A first attempt to determine the nitrogen to sulphur abundance gradient across the disk of our Galaxy
Results of an extensive spectrographic survey of galactic emissionregions are presented. The H II regions selected for the present studyare all large low-density nebulae similar to the ones which can beobserved spectrophotometrically in nearby galaxies. A radial increase inthe H-alpha/6584-A forbidden N II line-intensity ratio is found alongwith a radial decrease in the forbidden N II/forbidden S IIline-intensity ratio for a radial distance from the galactic center of 8to 14 kpc. The variation of the forbidden N II/forbidden S IIline-intensity ratio indicates a nitrogen-to-sulfur abundance gradientacross the disk of our Galaxy. This gradient is found to be similar tothe one observed in M 33.
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A Comparison between Radio and Optical Radial Velocities of H N Regions
Abstract image available at:http://adsabs.harvard.edu/abs/1970A&A.....7..322G
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The Effective Temperatures of the O Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969ApJ...158..629M&db_key=AST
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Interstellar Reddening for H II Regions and Lyman-Visual Colors of Their Exciting Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...153..743G&db_key=AST
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Spectral Types and Hγ Observations for Stars in Eight Associations
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Radial Velocities and Kinematics of Galactic H II Regions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...151..473M&db_key=AST
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The stellar distribution in the galactic anticenter.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967AJ.....72.1199M&db_key=AST
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A catalogue of discrete sources observed at 400 Mc/s
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Catalogue of radio sources in the galactic plane
Abstract image available at:http://adsabs.harvard.edu/abs/1963AJ.....68..181W
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Die räumliche Verteilung von 55 H II-Regionen in der Milchstraβe. Mit 1 Textabbildung
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A Survey of Galactic Radiation at 960 Mc/s
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The distances and dimensions of IC 1805, IC 1848, and IC 410.
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