Survey Plates Research Articles

The Digital Archive of the Photographic Images of the Córdoba Observatory Plates Collections

The astronomical events registered in photographic plates are unique. A remarkable interest in using old plates in many areas of the current astronomical research is widely recognized by the IAU. There are almost ten thousand plates in several collections at the Cordoba Observatory and most of them are nearly one century old. This photographic material is difficult to handle in order to get the information stored in it. The goal of this project is to make a digital archive of images of these collections. In this first survey plates are being scanned with a standard commercial transparency scanner. These low spatial resolution, low digital resolution and low signal-to-noise ratio images are intended for facilitating handling and visual inspection. However, one arc-second positions can be obtained. Photometric quality has not been yet determined. Otherwise high quality digital images can be acquired with a microdenstitometer based on a scientific grade CCD whose implementation is at its final stage. The possibility of using a better-performance scanner is being evaluated. It is planned to permit the access to low-resolution images via internet. High-resolution images of selected zones will be available upon request. At this first stage, collections totally digitized at low resolution are:Carte du Ciel and Small Magellanic Cloud Zones. Gaviola's Eta Carinae Spectra and Pulkovo Zones are still in process.

Searching for unknown open clusters in the Tycho-2 catalog

We present 11 new open cluster candidates found in a systematic search for unknown star clusters using the astrometric and photometric data included in the Tycho 2 catalog. The possible existence of these stellar aggregates is supported by the analysis of proper motions, color–magnitude diagrams, stellar density distributions, and by the visual inspection of the Digitized Sky Survey (DSS) plates. With these tools we were able to determine mean absolute proper motions as well as preliminary reddenings, distances and ages for the majority of the candidates. We found that most of them are possibly nearby (closer than ~600 pc) open clusters never studied before.

The early stages of NOVA Oph 2003 (V2573 Oph)

Intermediate resolution spectroscopy of NOVA Oph 2003 (V2573 Oph), which was first detected March 21th 2003 but reported July 19th 2003, obtained 19th to 23rd of July is presented here. The photometry during the early phases of the object is shortly discussed. We also retrieved very accurate astrometry of the target in this crowded field. This is needed to be able to do further observations of the post-nova during the next years. The inspection of the sky survey plates gives a possible progenitor candidate and allows to derive a lower limit for the outburst magnitude of about 10. 0. The spectrum shows an overall expansion of 2200 km s −1 and has clearly complex outflow substructures. The spectroscopy identifies this object as classical

The multiplicity function of galaxies

The multiplicity function (MF) of groups and clusters of galaxies is determined using galaxy catalogues extracted from a set of Digitized Palomar Sky Survey (DPOSS) plates. The two different types of structures (of low and high richness) were identified using two different algorithms: a modified version of the van Albada method for groups, and a peak finding algorithm for larger structures. In a 300 sq. deg. area up to z<0.2, we find 2944 groups and 179 clusters. Our MF covers a wide range of richnesses, from 2 to 200, and the two MF's derived by the two algorithms match smoothly without the need for additional conditions or normalisations. The resulting multiplicity function, of slope alpha= -2.08 +- 0.07, strongly resembles a power law.

A study of 11 newly discovered and 11 poorly known open clusters in the solar vicinity

We present the first determination of fundamental parameters (positions, reddenings, distances, ages and kinematics) for a sample of 22 open clusters in the solar vicinity. A systematic search for unknown open clusters using the astrometric and photometric data included in the Tycho2 catalogue has resulted in the identification of several candidates. In this work, we introduce 11 of the most promising open cluster candidates. The reality of the stellar aggregates is supported by the analysis of proper motions, colour-magnitude diagrams, stellar density distributions, and by the visual inspection of the Digitised Sky Survey (DSS) plates. The proper motion data included in the Tycho2 catalogue has also allowed us to identify members in 11 open clusters for which no information, besides their positions and estimates of their apparent diameters, was previously available. Reddenings, distances and ages were determined for most objects using colour-magnitude diagrams for cluster members, built using the photometry included in Tycho2, complemented by spectral types found in the literature. We find that the majority of the aggregates are nearby (closer than ~500 pc) open clusters.

The Southern Dwarf Hunt: Local Group Dwarf Candidates in the Southern Sky

We present observations of 82 Local Group dwarf galaxy candidates, of which 62 were chosen visually from ESO-SRC survey plates of the southern sky (32 of which were not previously cataloged) and the rest suggested by various sources in the literature. Two are the Local Group galaxies Antlia and Cetus; nine are more distant galaxies, though still within a few megaparsecs; 45 are background galaxies; seven are planetary (or other emission) nebulae; 15 are reflection or other Galactic nebulae; two are galaxy clusters; one is a Galactic star cluster; and one is a misidentified star. We conclude that there is no large population of faint Local Group dwarf galaxies of any familiar type awaiting discovery. We point out the danger of relying on a single type of data to reach conclusions about an object.

The Optical Proper Motions of HH 7–11 and Cepheus E

A key ingredient in understanding the dynamics of stellar outflows is their proper motion. We have used optical images in the [S II] emission at 6717/6731 A and the red Digitized Palomar Observatory Sky Survey (DSS) plates to determine the proper motion of the HH 7–11 system and the optical knot of Cep E (HH 377). The DSS plate measurements span nearly 37 years for both HH 7–11 and HH 377 and have a wide field of view, which allows an accurate determination of the proper motions despite their relatively low angular resolution. The optical images, with higher angular resolution, cover a shorter period, 7 and 4 years, respectively, for HH 7–11 and HH 377 and have been used to complement the DSS measurements. From the DSS plates we have found that HH 377 has a proper motion of 0031 ± 0003 yr-1 with P.A. = 206°; i.e., it is moving away from IRAS 230111+63, which at a distance of 730 pc corresponds to a tangential velocity of 107 ± 14 km s-1. The values obtained from the optical images are consistent with these measurements. Similarly, the proper motions of HH 7–11 range from 0015 ± 0009 yr-1 (HH 9) to 0044 ± 0007 yr-1 (HH 11), and the flow is moving away from SVS 13 with mean P.A. ~ 136°. At a distance of 330 pc, these motions correspond to tangential velocities of ~25–70 km s-1, i.e., comparable to the original values obtained by Herbig & Jones (1983). The measurements from the optical CCD [S II] images are again consistent with these motions, although in detail there are some differences, particularly for HH 7 and HH 10.

Automated Selection of Metal‐poor Stars in the Galaxy—The HK‐II Survey

Automated Selection of Metal‐poor Stars in the Galaxy—The HK‐II Survey

High and Low Surface Brightness Galaxies in the Local Universe. IV. Optical and 21 Centimeter Spectroscopy

We present flux-calibrated spectra in the range 3500 to 8000 A for the nuclear regions of 250 galaxies and H I 21 cm line profiles for 238 galaxies selected from the catalog of low surface brightness galaxies identified in Automated Plate Measuring Facility (APM) scans of UK Schmidt Telescope survey plates. For the optical spectra, common nebular absorption- and emission-line equivalent widths and emission-line fluxes were measured with typical errors of about 20%. H I mass and velocity widths were measured from the 21 cm line emission, with 15% accuracy. Galaxies in this study span over 6 mag in surface brightness. Only about 20% of these galaxies show spectroscopic evidence of active galactic nuclei. Derived quantities such as synthetic colors, metallicity, star formation rate, the ratio of neutral hydrogen mass to blue light, and gas mass fraction are presented in a companion paper.

An all-sky set of $\vec (B)-V-R$ photometric calibrators for Schmidt surveys

We publish 622 CCD photometric sequences in the Johnson-Kron-Cousins standard system, distributed both in the northern and southern hemispheres, useful for the calibration of photographic photometry of Schmidt survey plates. The collection and reduction of the CCD data presented here are part of a long-term program devoted to the construction of the Second Guide Star Photometric Catalog (GSPC-II). The GSPC-II is an all-sky catalog of photometric stellar sequences with a limiting magnitude of V = 19 or fainter, in the (B), V ,a nd R passbands of the Johnson-Kron-Cousins system. Standard photometric errors are at the level of0.07 for a V 19 magnitude star. These sequences are being used by teams of the Space Telescope Science Institute (STScI) and the Osservatorio Astronomico of Torino (OATo) for the photometric calibration of the Second Guide Star Catalog.

Frequency Dependence of the Parsec-scale Polarization Structures of BL Lac Objects

BL Lacertae objects are active galactic nuclei with weak or undetectable line emission and strong variability in total intensity and linear polarization over a wide wavelength range from optical to radio. The radio emission and much of the optical emission is believed to be synchrotron radiation. Sources in the complete sample of BL Lac objects defined by Kühr and Schmidt (1990) have: 5 GHz fluxes of at least 1 Jy, radio spectral index α ≥ −0.5 (Sv ˜ v+α), rest frame equivalent width of the strongest emission lines less than 5 Å, and optical counterparts on the Sky Survey plates with brightness greater than 20m.

Mass‐to‐Light Ratios of Groups and Clusters of Galaxies

We constrain the mass-to-light ratios, gas mass fractions, baryon mass fractions and the ratios of total to luminous mass for a sample of eight nearby relaxed galaxy groups and clusters: A262, A426, A478, A1795, A2052, A2063, A2199 and MKW4s. We useASCA spatially resolved spectroscopic X-ray observations and ROSAT PSPC images to constrain the total and gas masses of these clusters. To measure cluster luminosities we use galaxy catalogs resulting from the digitization and automated processing of the second generation Palomar Sky Survey plates calibrated with CCD images in the Gunn-Thuan g, r, and i bands. Under the assumption of hydrostatic equilibrium and spherical symmetry, we can measure the total masses of clusters from their intra-cluster gas temperature and dens ity profiles. Spatially resolved ASCA spectra show that the gas temperature decreases with increasing distance from the center. By comparison, the assumption that the gas is isothermal results in an underestimate of the total ma ss at small radii, and an overestimate at large cluster radii. We have obtained luminosity functions for all clusters in our sample. After correcting for background and foreground galaxies, we estimate the total cluster luminosity using Schechter function fits to the galaxy catalogs. In the three lowest redshift clusters where we can sample to fainter absolute magnitudes, we have detected a flattening of the luminosity function at intermediate magni tudes and a rise at the faint end. These clusters were fitted with a sum of two Schechter functions. The remaining cl usters were well fitted with a single Schechter function. Assuming H0 = 50 h50 km s -1 Mpc -1 , the measured mass-to-light ratios are ∼ 100 h50 M⊙/L⊙. This, along with a high baryonic fraction, is indicative of a low density universe with 0 ∼ 0.15 - 0.2. Subject headings: Cosmology — galaxies: clusters: individual — intergalactic medium — X-rays: galaxies

The APM Survey for cool carbon stars in the Galactic halo -- II. The search for dwarf carbon stars

We present proper motion measurements for carbon stars found during the APM Survey for Cool Carbon Stars in the Galactic Halo (Totten & Irwin, 1998). Measurements are obtained using a combination of POSSI, POSSII and UKST survey plates supplemented where necessary by CCD frames taken at the Isaac Newton Telescope. We find no significant proper motion for any of the new APM colour-selected carbon stars and so conclude that there are no dwarf carbon stars present within this sample. We also present proper motion measurements for three previously known dwarf carbon stars and demonstrate that these measurements agree favourably with those previously quoted in the literature, verifying our method of determining proper motions. Results from a complimentary program of JHK photometry obtained at the South African Astronomical Observatory are also presented. Dwarf carbon stars are believed to have anomalous near-infrared colours, and this feature is used for further investigation of the nature of the APM carbon stars. Our results support the use of JHK photomtery as a dwarf/giant discriminator and also reinforce the conclusion that none of the new APM-selected carbon stars are dwarfs. Finally, proper motion measurements combined with extant JHK photometry are presented for a sample of previously known Halo carbon stars, suggesting that one of these stars, CLS29, is likely to be a previously unrecognised dwarf carbon star.

The ROSAT International X-ray/Optical Survey (RIXOS): source catalogue

We describe the ROSAT International X-ray/Optical Survey (RIXOS), a medium-sensitivity survey and optical identification of X-ray sources discovered in ROSAT high Galactic latitude fields (|b|>28°) and observed with the Position Sensitive Proportional Counter (PSPC) detector. The survey made use of the central 17 arcmin of each ROSAT field. A flux limit of 3×10−14 erg cm−2 s−1 (0.5–2 keV) was adopted for the survey, and a minimum exposure time of 8000 s was required for qualifying ROSAT observations. X-ray sources in the survey are therefore substantially above the detection threshold of each field used, and many contain enough counts to allow the X-ray spectral slope to be estimated. Spectroscopic observations of potential counterparts were obtained of all sources down to the survey limit in 64 fields, totalling a sky area of 15.77 deg2. Positive optical identifications are made for 94 per cent of the 296 sources thus examined. A further 18 fields (4.44 deg2), containing 105 sources above the 3×10−14 erg cm−2 s−1 survey limit, are completely optically identified to a higher flux of 8×10−14 erg cm−2 s−1 (0.5–2 keV). Optical spectroscopic data are supplemented by deep CCD imaging of many sources to reveal the morphology of the optical counterparts, and objects too faint to register on Sky Survey plates. The faintest optical counterparts have R∼22. This paper describes the survey method, and presents a catalogue of the RIXOS sources and their optical identifications. Finding charts based on Sky Survey data are given for each source, supplemented by CCD imaging where necessary.

Compact Stellar Systems in the Fornax Cluster: Super-massive Star Clusters or Extremely Compact Dwarf Galaxies?

AbstractWe describe a population of compact objects in the centre of the Fornax Cluster which were discovered as part of our 2dF Fornax Spectroscopic Survey. These objects have spectra typical of old stellar systems, but are unresolved on photographic sky survey plates. They have absolute magnitudes −13 &lt; MB &lt; −11, so they are 10 times more luminous than any Galactic globular clusters, but fainter than any known compact dwarf galaxies. These objects are all within 30 arcminutes of the central galaxy of the cluster, NGC 1399, but are distributed over larger radii than the globular cluster system of that galaxy. We suggest that these objects are either super-massive star clusters (intra-cluster globular clusters or tidally stripped nuclei of dwarf galaxies) or a new type of low-luminosity, compact elliptical dwarf (‘M32-type”) galaxy. The best way to test these hypotheses will be to obtain high-resolution imaging and high-dispersion spectroscopy to determine their structures and mass-to-light ratios. This will allow us to compare them to known compact objects and establish whether they represent a new class of hitherto unknown stellar system.

A New Local Group Galaxy in Cetus

We report the discovery of a previously uncataloged Local Group galaxy in the constellation Cetus. Faintly visible on UKST survey plates, it has a smooth, diffuse appearance and appears to be a dwarf spheroidal of type dE3.5. A color-magnitude diagram in V, V-I shows a clear giant branch but no sign of recent star formation. From the position of the tip of the giant branch, we derive a reddening-corrected distance modulus of 24.45 ± 0.15 and a metallicity of -1.9 ± 0.2. With an implied heliocentric distance of 775 ± 50 kpc, and a corresponding Local Group barycentric distance of 615 kpc, the Cetus dwarf lies well within the boundaries of the Local Group, and although it currently lacks a radial velocity measurement, it is undoubtedly a member of the Local Group. The nearest Local Group galaxies are WLM and IC 1613 at angular separations of 73 and 163 and roughly 175 and 230 kpc total distance, respectively. Although the Cetus dwarf is unlikely to be directly associated with any other Local Group galaxy, it does lie in the general direction of the extension of the Local Group toward the Sculptor Group.

X-Ray Nova XTE J1550−564: Optical Observations

We report the identification of the optical counterpart of the X-ray transient XTE J1550-564 described in two companion papers by Sobczak et al. and Remillard et al. We find that the optical source brightened by ≈4 mag over the quiescent counterpart seen at B≈22 on a SERC survey plate and then decayed by ≈1.5 mag over the 7 week-long observation period. There was an optical response to the large X-ray flare described by Sobczak et al., but it was much smaller and delayed by ≈1 day.

The Fornax Spectroscopic Survey: The Number of Unresolved Compact Galaxies

We describe a sample of thirteen bright (18.5<Bj<20.1) compact galaxies at low redshift (0.05<z<0.21) behind the Fornax Cluster. These galaxies are unresolved on UK Schmidt sky survey plates, so would be missing from most galaxy catalogs compiled from this material. The objects were found during initial observations of The Fornax Spectroscopic Survey. This project is using the Two-degree Field spectrograph on the Anglo-Australian Telescope to obtain spectra for a complete sample of all 14000 objects, stellar and non-stellar, with 16.5<Bj<19.7, in a 12 square degree area centered on the Fornax cluster of galaxies. The surface density of compact galaxies with magnitudes 16.5<Bj<19.7 is 7+/-3 /sq.deg., representing 2.8+/-1.6% of all local (z<0.2) galaxies to this limit. There are 12+/-3 /sq.deg. with 16.5<Bj<20.2. They are luminous (-21.5<Mb<-18.0, for H0=50 km/s/mpc) and most have strong emission lines (H alpha equivalent widths of 40-200 A) and small sizes typical of luminous HII galaxies and compact narrow emission line galaxies. Four out of thirteen have red colors and early-type spectra, so are unlikely to have been detected in any previous surveys.

Found: High Surface Brightness Compact Galaxies

AbstractWe are using the 2dF spectrograph to make a survey of all objects (“stars” and “galaxies”) in a 12 deg2 region towards the Fornax cluster. We have discovered a population of compact emission-line galaxies unresolved on photographic sky survey plates and therefore missing in most galaxy surveys based on such material. These galaxies are as luminous as normal field galaxies. Using Hα to estimate star formation they contribute at least an additional 5% to the local star formation rate.

Unified Scheme for Seyferts or the Influence of Interactions?

The first statistical study of the environment of Seyfert galaxies (of both types 1 and 2) was done by Petrosian (1982), who found that Sy2 galaxies had an excess of nearby companion galaxies with respect to field galaxies. Dahari (1985) made a similar study, and obtained that both types of Seyfert galaxies are found five times more often in interacting systems that “normal” galaxies. Fuentes-Williams &amp; Stocke (1988) obtained the opposite result: that Seyfert galaxies have no significative excess of nearby companions, and MacKenty (1989) obtained the same result as Petrosian. The last papers appeared in 1995: Rafanelli, Violato &amp; B.aruffolo (1995) obtained a similar result as Dahari. Laurikainen &amp; Salo (1995) made a careful attempt to understand the discrepancies; they concluded that the incompatibilities in the results were mainly due to control sample selection, and problems in background galaxy determination. Their work confirmed the result of the first study. However, in order to explain the discrepancies between previous results, they also used incorrectly defined control samples. Objections can be made against all of these works for this only reason. We have repeated the study using, for the first time, the digitized Palomar Sky Survey plates (paSS), an automated selection procedure, and correctly defined control samples (Osterbrock 1993).