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L' and M' standard stars for the Mauna Kea Observatories Near-Infrared system
We present L' and M' photometry, obtained at the United Kingdom InfraredTelescope (UKIRT) using the Mauna Kea Observatories Near-Infrared(MKO-NIR) filter set, for 46 and 31 standard stars, respectively. The L'standards include 25 from the in-house `UKIRT Bright Standards' withmagnitudes deriving from Elias et al. and observations at the InfraredTelescope Facility in the early 1980s, and 21 fainter stars. The M'magnitudes derive from the results of Sinton and Tittemore. We estimatethe average external error to be 0.015 mag for the bright L' standardsand 0.025 mag for the fainter L' standards, and 0.026 mag for the M'standards. The new results provide a network of homogeneously observedstandards, and establish reference stars for the MKO system, in thesebands. They also extend the available standards to magnitudes whichshould be faint enough to be accessible for observations with moderndetectors on large and very large telescopes.
| Molecular Outflows in the Young Open Cluster IC 348
We present a wide-field survey of the young open cluster IC 348 formolecular H2 outflows. Outflow activity is only found at itssouthwestern limit, where a new subcluster of embedded sources is in anearly phase of its formation. If the IC 348 cluster had been built up bysuch subclusters forming at different times, this could explain thelarge age-spread that Herbig (1998) found for the IC 348 member stars.In addition to several compact groups of H2 knots, our surveyreveals a large north-south oriented outflow, and we identify the newlydiscovered far-infrared and millimeter object IC 348 MMS as its source.New deep images in the 1-0 S(1) line of molecular hydrogen trace the HH211 jet and counterjet as highly collimated chains of knots, resemblingthe interferometric CO and SiO jets. This jet system appears rotatedcounterclockwise by about 3° with respect to the prominentH2 bow shocks. Furthermore, we resolve HH 211-mm as a doublepointlike source in the millimeter continuum.Based on observations taken at the German-Spanish Astronomical Centre,Calar Alto, operated by the Max-Planck-Institute für Astronomie,Heidelberg, jointly with the Spanish National Commission for Astronomyand on observations with ISO, an ESA project with instruments funded byESA Member States (especially the PI countries: France, Germany, theNetherlands, and the United Kingdom) and with the participation of ISASand NASA.
| JHK Standard Stars on the CIT Photometric System
We present a set of 58 stars with JHK standard values on the CIT systemand with a suitable magnitude range for use with array detectors onsmall- to moderate-size telescopes. Each final value is based on six to47 measures (with a mean of 17) obtained on separate nights with the USNaval Observatory (USNO) NICMOS3 (HgCdTe) camera. The objects include 20primary CIT standards from Elias et al. and 38 secondary sourcesselected from the SAAO and UKIRT standards lists, cover a K-magnituderange between 6.0 and 10.8, and lie north of declination -20°. Thestars were reduced to the CIT system as defined by Elias et al.,producing a USNO system that is identical to the near-infrared CITsystem. This work densifies the original CIT system by nearly a factorof 3 and extends its range by about 3 mag. The SAAO and UKIRT standardsare also compared with the CIT system.
| High-Precision Near-Infrared Photometry of a Large Sample of Bright Stars Visible from the Northern Hemisphere
We present the results of 8 yr of infrared photometric monitoring of alarge sample of stars visible from Teide Observatory (Tenerife, CanaryIslands). The final archive is made up of 10,949 photometric measuresthrough a standard InSb single-channel photometer system, principally inJHK, although some stars have measures in L'. The core of this list ofstars is the standard-star list developed for the Carlos SánchezTelescope. A total of 298 stars have been observed on at least twooccasions on a system carefully linked to the zero point defined byVega. We present high-precision photometry for these stars. The medianuncertainty in magnitude for stars with a minimum of four observationsand thus reliable statistics ranges from 0.0038 mag in J to 0.0033 magin K. Many of these stars are faint enough to be observable with arraydetectors (42 are K>8) and thus to permit a linkage of the bright andfaint infrared photometric systems. We also present photometry of anadditional 25 stars for which the original measures are no longeravailable, plus photometry in L' and/or M of 36 stars from the mainlist. We calculate the mean infrared colors of main-sequence stars fromA0 V to K5 V and show that the locus of the H-K color is linearlycorrelated with J-H. The rms dispersion in the correlation between J-Hand H-K is 0.0073 mag. We use the relationship to interpolate colors forall subclasses from A0 V to K5 V. We find that K and M main-sequence andgiant stars can be separated on the color-color diagram withhigh-precision near-infrared photometry and thus that photometry canallow us to identify potential mistakes in luminosity classclassification.
| Near-Infrared Photometric Survey of Proto-planetary Nebula Candidates
We present JHK' photometric measurements of 78 objects mostly consistingof proto-planetary nebula candidates. Photometric magnitudes aredetermined by means of imaging and aperture photometry. Unlike theobservations with a photometer with a fixed-sized beam, the method ofimaging photometry permits accurate derivation of photometric values,because the target sources can be correctly identified and confusionwith neighboring sources can be easily avoided. Of the 78 sourcesobserved, we report nearly 10 cases in which the source seems to havebeen misidentified or confused by nearby bright sources. We also presentnearly two dozen cases in which the source seems to have indicated avariability that prompts a follow-up monitoring. There are also a fewsources that show previously unreported extendedness. In addition, wepresent H-band finding charts of the target sources.
| H II Emission from a Complete Spectroscopic Survey of Be Stars in h and χ Persei
We describe data for emission-line B stars observed in a spectroscopicsurvey of h and χ Persei. The survey is complete to V=12.5 andcovers an area of ~1100 arcmin2 roughly centered on the twoclusters. We detect 32 Be stars; some have low Hα emissionstrength. Seven of these are new identifications; seven others areconfirmations of Be stars previously identified using photometry. Fiveof the observed Be stars show significant Hα profile variationsfrom epoch to epoch. We show that spectral indices yield physicalcharacteristics of the H II emission region. This automatic method isrobust and easily applied to large spectroscopic samples. We inferHα:Hβ flux ratios of 2-5 and observe a linear relationshipbetween Hα emission and J-K color for these stars. We include aHertzsprung-Russell diagram for the B-type stars in the clusters.
| A Survey of Near Infrared Nebulosities around Luminous Young Stellar Objects: J, H, and K' Imaging
We present J, H, and K' images of 45 IRAS sources in the recent list byCampbell, Persson, & Matthews, which have been presumed to beluminous young stellar objects (YSOs) because of their infrared colorsand their large IRAS fluxes. These objects have been classified intofour groups according to two dust features in the 3 μm band-theH2O ice absorption and the unidentified infrared band (UIB)emission. Our near-infrared images reveal that most of them (42/45) havenebulosity in at least one of the three bands. By examining thenebulosities around these YSOs, we find that (1) nebulae around theobjects with the ice absorption can be explained by the scattered lightof the central stars, (2) nebulae around the objects with the UIBemission cannot be explained by the scattered light alone-additionalemission, most likely from very small grains, is necessary to explainthe nebular colors and the surface brightness, and (3) the objects withneither the ice absorption nor the UIB emission tend to have faint or nonebulosity. We interpret the variation of nebular brightness and thecolor as evolutionary phases of circumstellar matter of intermediate- tohigh-mass YSOs.
| K'-Band Polarimetric Imaging of S187 IR and S233
K'-band polarimetric images of star-forming regions S187 IR and S233 arepresented. In S187 IR, a bipolar, near-infrared nebula is observedaround IRAS 01202+6133, with the southern part being bright and knotty,and the northern part being faint and filamentary. The polarizationpattern shows that the nebula is illuminated by a single near-infraredsource, which is associated with IRAS 01202+6133. A polarization disk isfound around this source with the disk plane roughly perpendicular tothe axis of the bipolar nebula. We conclude that this source is thedriving source of the outflow in the region. Two nebulae are detected inthe S233 region. Associated with a compact infrared cluster, S233 A isroughly round in shape and shows a weak polarization pattern. The S233 Bnebula shows roughly elongated geometry in the east-west direction. Thepolarization vectors divide it into three parts. Each part hasdistinctly different polarization from the others. The northeastern partof S233 B exhibits a centrosymmetric polarization pattern around acentroid, at which we locate a deeply embedded source (DES) undetectedin the K' band and shorter wavelengths. The DES is likely the excitingsource of water masers and outflows in the S233 B region. The westernpart of the nebula shows a parallel polarization pattern, but thesoutheastern part displays very little polarization. Comparison of themorphology and polarization of the nebulae in different star-formingregions suggests a close relationship between the evolutionary sequenceof the young stellar objects and the morphology of the associatednebulae.
| Unveiling Deeply Embedded Sources by Near-Infrared Polarimetric Imaging
Near-infrared polarimetric images are presented for six molecularoutflow sources: IRAS 20050+2720, IRAS 20126+4104, IRAS 20188+3928,S233, AFGL 5180, and AFGL 6366S. All the regions are found to exhibitreflection nebulae and to be associated with massive and clustered starformation. By inspecting polarimetric patterns in the nebulae, we haveidentified six deeply embedded sources (DESs) which illuminatecircumstellar nebulosity but are not detectable in wavelengths shorterthan 2 μm. While the DES in IRAS 20050 coincides with an infraredsource in a previous, longer wavelength observation and the one in IRAS20126 with a hot molecular core, the nature of the other newlydiscovered DESs is not known. From the compilation of the observationsof DESs over a large wavelength range, we suspect that the DESs possesscharacteristics similar to hot molecular cores and are likely to be inthe pre-ultracompact H II region phase of massive star formation.
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| Near-Infrared Imaging of the Star-forming Region AFGL 5157
We present near-infrared images of the star-forming region AFGL 5157 inthe JHK' broadband filters and H_2 v=1-0 S(1) narrowband filter. Theimages reveal a dense cluster of stars and infrared nebulositiesassociated with previously known infrared sources. Of 54 near-infraredsources detected in the nebula, NGC 1985, 12 exhibit infrared excessestypical of T Tauri stars, Herbig Ae/Be stars, and protostars. Themagnitude and color distribution of the cluster of stars in the nebulaare found to be different from those outside the nebular region. TheK'-magnitude distribution of the cluster is quite flat, while thenoncluster is peaked toward the low magnitude. The [H-K'] color of thecluster also displays 0.3 mag redder than that of the noncluster. Theinfrared nebula displays a bright nucleus with two spirals extended tothe north and south. In light of the color properties of the nebula, wepropose a shell model for the nebular structure that could be formed bystar-forming activity of the central cluster. Many sources with infraredexcesses are found to be embedded in the shell structure. Twelve shockedknots in H_2 emission are observed in the region. The nonaxisymmetricdistribution of the knots indicates the presence of multiple outflows inthe region. Although we failed to identify the powering sourcesresponsible for some of the HH-like objects, the relationship of the H_2emission with infrared sources shows that there must be severalspatially separated sources exciting the shocked H_2 emission as well asthe previously observed H_2O masers and molecular outflow. Diffuse H_2emission is also detected on the shell structure, which supports theshell model of the nebula. This diffuse emission could result fromfluorescence by relatively evolved stars in the cluster.
| Towards a fundamental calibration of stellar parameters of A, F, G, K dwarfs and giants
I report on the implementation of the empirical surface brightnesstechnique using the near-infrared Johnson broadband { (V-K)} colour assuitable sampling observable aimed at providing accurate effectivetemperatures of 537 dwarfs and giants of A-F-G-K spectral-type selectedfor a flux calibration of the Infrared Space Observatory (ISO). Thesurface brightness-colour correlation is carefully calibrated using aset of high-precision angular diameters measured by moderninterferometry techniques. The stellar sizes predicted by thiscorrelation are then combined with the bolometric flux measurementsavailable for a subset of 327 ISO standard stars in order to determineone-dimensional { (T, V-K)} temperature scales of dwarfs and giants. Theresulting very tight relationships show an intrinsic scatter induced byobservational photometry and bolometric flux measurements well below thetarget accuracy of +/- 1 % required for temperature determinations ofthe ISO standards. Major improvements related to the actual directcalibration are the high-precision broadband { K} magnitudes obtainedfor this purpose and the use of Hipparcos parallaxes for dereddeningphotometric data. The temperature scale of F-G-K dwarfs shows thesmallest random errors closely consistent with those affecting theobservational photometry alone, indicating a negligible contributionfrom the component due to the bolometric flux measurements despite thewide range in metallicity for these stars. A more detailed analysisusing a subset of selected dwarfs with large metallicity gradientsstrongly supports the actual bolometric fluxes as being practicallyunaffected by the metallicity of field stars, in contrast with recentresults claiming somewhat significant effects. The temperature scale ofF-G-K giants is affected by random errors much larger than those ofdwarfs, indicating that most of the relevant component of the scattercomes from the bolometric flux measurements. Since the giants have smallmetallicities, only gravity effects become likely responsible for theincreased level of scatter. The empirical stellar temperatures withsmall model-dependent corrections are compared with the semiempiricaldata by the Infrared Flux Method (IRFM) using the large sample of 327comparison stars. One major achievement is that all empirical andsemiempirical temperature estimates of F-G-K giants and dwarfs are foundto be closely consistent between each other to within +/- 1 %. However,there is also evidence for somewhat significant differential effects.These include an average systematic shift of (2.33 +/- 0.13) % affectingthe A-type stars, the semiempirical estimates being too low by thisamount, and an additional component of scatter as significant as +/- 1 %affecting all the comparison stars. The systematic effect confirms theresults from other investigations and indicates that previousdiscrepancies in applying the IRFM to A-type stars are not yet removedby using new LTE line-blanketed model atmospheres along with the updatedabsolute flux calibration, whereas the additional random component isfound to disappear in a broadband version of the IRFM using an infraredreference flux derived from wide rather than narrow band photometricdata. Table 1 and 2 are only available in the electronic form of thispaper
| Multiwavelength Observations of Collisional Ring Galaxies.I.Broad-Band Images, Global Properties, and Radial Colors of the Sample Galaxies
This is one of a series of papers discussing the optical, infrared andradio continuum properties of a sample of collisional ring galaxies. Thepresent paper concentrates on the global broad-band optical (B, V and R)and near-IR (J, H and K) images of the galaxies and describe theirglobal properties. An analysis of the colors of the galaxies over avariety of wavelength baselines is described. In the B and V bands, thebluest colors are found in the outer bright ring. The B-V colors of thesample of galaxies are blue, the median value for the sample is B-V =0.60, and V-K= 2.33 mag. The IR morphology of the galaxies is, in mostcases, very similar to that of the B-band data, suggesting that theclumpy appearance of the star formation in the outer rings is real, andnot a result of patchy dust obscuration. Only in one ring (WN1, aSeyfert ring galaxy) was the IR morphology different from the optical,suggesting the presence of significant dust in the disk. In II Hz 4,faint spiral arms are seen within the ring. There is a suggestion thatthe larger rings have redder V-K colors, which may be due to anincreased incidence of nuclear bulges in larger ring galaxies. Radialprofiles of surface brightness and color are presented for fourgalaxies. In all cases, the colors becomes bluer as one proceedsradially outwards, but in two galaxies, the rings redden again outsidethe main ring, suggesting the existence of a red stellar population thatmay have pre-dated the collisions.
| Optical, infrared and millimetre-wave properties of Vega-like systems.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996MNRAS.279..915S&db_key=AST
| An Infrared Study of the Star-forming Region IRAS 05380-0728
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...461..909C&db_key=AST
| A Butterfly in the Making: Revealing the Near-Infrared Structure of Hubble 12
Abstract image available at:http://adsabs.harvard.edu/abs/1996ApJ...461..288H
| Forbidden Fe^+ emission from supernova remnants in M33
Supernova remnants are known to be luminous sources of infrared [FeII]emission. By studying how the luminosity scales with age, environmentand other relevant factors, we can construct an [FeII] luminosityfunction for supernova remnants. This will enable us to predictsupernova rates in starburst galaxies that are too distant forindividual remnants to be resolved. First, however, we require accurateluminosities for a sample of remnants of varying ages, and in varyingphysical environments. As part of this project, we have carried out aninitial study of a small sample of evolved (ages greater than a fewthousand years) remnants in M33. From these data we tentatively concludethat there is evidence for the peak luminosity in the [FeII] lines ofthese sources to arise in a narrow range of ages. In other respects, theM33 remnants are similar to their galactic and Magellanic Cloudcounterparts in the observed peak luminosity. From this, and internalevidence as to the environment present in these regions, we concludethat the luminosity of evolved remnants is only marginally dependent ondensity and metallicity.
| Multiwavelength observations of ring galaxies. 2: Global star formation in ring galaxies
We present optical H-alpha emission-line images and K band near-infraredimages of a sample of collisionally formed ring galaxies. These are usedto determine the distribution of star formation and the distribution ofthe old stellar population, respectively, in the galaxies. Our resultsshow ring galaxies to have similar Hcx luminosities to starburstgalaxies, with star formation being contained almost exclusively in thering. In the larger ring galaxies we observe the ionized hydrogen to lieon the outer edge of the underlying, broader, K band ring. No conclusiveevidence is found in our sample for a true underlying stellar densitywave. Rather, the evidence suggests that either the density waves havepassed into the outer, mainly H I disk of the galaxies or that theprogenitor galaxies were mainly gas-rich low surface brightness objectsand that most of the optical/IR light we now observe has resulted fromrecent star formation in the expanding ring.
| A K' imaging survey of molecular outflow sources
A K'-band imaging survey with a approximately equals 8 min x 3 min fieldof view of all regions associated with CO molecular outflow from thelist of Fukui (1989) has been conducted. We present the individualimages and describe individual nebulous objects and star clusters. Thedata, including photometric calibration data, are being published asFITS files on a CD-ROM. The vast majority of all outflow sources areassociated with nebulosity detectable in K', so such nebulae can be usedas tracers for very young stars. We find a significant fraction(one-third) of molecular outflow sources to be associated with clustersof young stars. Most of the young embedded clusters show peaks in theirK' magnitude histograms that, if interpreted as an evolutionary effect,indicate average ages of the embedded star population of is less than 1x 106 yr.
| Interstellar medium and star formation in the nearby QSO I ZW 1
We report the first detection of the millimeter (13)CO(1-0) and thenear-infrared H2 v = 1-0 S(1) line from the QSO I Zw 1. We also presentupper limits on the 1.6435 micrometer (Fe II) and 1.9615 micrometer (SiVI) line as well as high-resolution near-infrared continuum data on itsnucleus. We interpret the results in light of previously published(12)CO data on this source and common properties of the far-infrared andmolecular line emission of external, luminous infrared galaxies. Wepropose a two-component model for the molecular line emission in which acore and disk component have similar contributions. In this model thenucleus is dominated by emission from warm, (mostly) optically thickmolecular gas, whereas the line emission in the disk is mostly due tocold, probably subthermally excited molecular gas. We also confirm theneed for a two-component model for I Zw 1 in which about 2/3 of thefar-infrared luminosity originates in the disk and 1/3 originates in thenucleus. We estimate star-forming rate and efficiency for the disk andthe nucleus of the I Zw 1 host galaxy and find that the values for bothare comparable to those of luminous IRAS galaxies. Over the whole diskthe star formation efficiency is close to the maximum value of approx. =30 solar luminosity/solar mass found in Galactic star-forming regionslike M17 or W51. Analysis of the nuclear near-infrared colors suggests amixture of a QSO nucleus and an extincted stellar component contributingabout 10%-20% of the flux density at 2.2 micrometer. This results in anestimate of the molecular bulge size of the order of 1 sec to 2 sec(1.2-2.4 kpc). However, the presence of the QSO nucleus in I Zw 1 isclearly related to the nucleus would be blocked by obscuring material, IZw 1 would be seen as a luminous IRAS galaxy.
| The lowest mass stars in the Hyades
In Bryja et al. (1992), we presented proper motions and photometry of 12very low mass star and brown dwarf candidates in the Hyades cluster,selected on the basis of colors and proper motions measured from threeepochs of plate material. We here present new observations of some ofthese candidates, including seven low resolution spectra, plus motionsand photometry of 17 fainter additional candidates. Most of thecandidates have JHK colors typical of M5-M8 dwarfs, while their opticalcolors are consistent with earlier M spectral types. The availablespectra consist of late M dwarfs with H alpha emission featuresindicative of Hyades membership, earlier M dwarf background stars, andtwo anomalous objects with early M dwarf features but unusually redcontinua. We find that the proper motion distribution of faint red fieldstars in the region is irregular, and it is not possible to determine ifthe anomalous objects are Hyades members or background field stars. Inthe most conservative view, only five of our 29 candidates are Hyades.These five stars have optical and infrared colors consistent with thebottom of the Hyades main sequence, with four of them also shown to havelate M dwarf spectra. It follows that these are the lowest mass starsknown in the Hyades (M is about 0.1 solar mass).
| A filter for deep near-infrared imaging
The K passband (central wavelength 2.2 microns, FWHM 0.4 micron) is thelongest wavelength standard near-IR passband through which deepground-based imaging is possible. Thermal emission from telescope,instrument, and sky limits the depth to which such imaging can reach byproducing strongly temperature-dependent backgrounds in the range11-13.5 mag/sq arcsec. This paper describes how a passband, which isdenoted as K-prime, located slightly shortward of the standard Kpassband (central wavelength 2.1 microns), yet still within the sameatmospheric window, leads to a significantly lower thermal component ofthe background, reducing the background surface brightness by up to 0.9mag sq arcsec, and thereby allowing deeper imaging to be obtained in thesame integration time. The photometric differences between the K-primefilter and the standard K filter are discussed.
| A 2.2 micron survey in the L1630 molecular cloud
A 2.2 micron survey of a significant portion of the L1630 molecularcloud was carried out using the NOAO infrared array camera on the KittPeak 1.3 m telescope. This survey is estimated to be complete to 13thmagnitude at K, which corresponds to a main-sequence star of about 0.6solar mass. Therefore this survey has provided a sensitive census of theyoung stellar objects within this molecular cloud. As a result, 912sources having m(K) less than 13.0 have been detected. It is estimatedthat 50 percent of these sources are associated with the molecularcloud. These sources are not distributed uniformly throughout thesurveyed region but rather appear grouped or clustered. In fact, fourembedded infrared clusters were identified. These clusters contain atleast 58 percent but possibly as much as 96 percent of the total numberof sources associated with this molecular cloud suggesting that thedominant mode of star formation in this region is in clusters.
| Infrared standard stars
The results of an observational program aimed at setting up a network offaint near-infrared standards of sufficient accuracy are reported. Thenetwork covers both northern and southern hemispheres and includesstandards red enough to provide at least a limited check on colortransformations. The standards are set up at J (1.2 micron), H (1.6micron), K (2.2 microns), and L (3.5 microns), and their H2O and COmolecular absorption indices are determined. The problem of colortransformations between observatories is discussed briefly. Allmagnitudes presented are transformed to the natural system defined bythe CIT observations.
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| קבוצת-כוכבים: | דגים |
| התרוממות ימנית: | 00h33m39.53s |
| סירוב: | +20°26'01.7" |
| גודל גלוי: | 7.857 |
| מרחק: | 142.45 פארסק |
| תנועה נכונה: | 3.7 |
| תנועה נכונה: | 1.4 |
| B-T magnitude: | 8.205 |
| V-T magnitude: | 7.886 |
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