CCD standards for U and I in the open cluster
 NGC 7790

Petrov, G. T.; Seggewiß, W.; Dieball, A.; Kovachev, B.

doi:10.1051/0004-6361:20011001

“…We used the clusters M 92 3 (Majewski et al 1994), NGC 7790 (Odewahn et al 1992;Petrov et al 2001),k and M 67 (Chevalier & Ilovaisky 1991) for this purpose. We performed aperture stellar photometry of the standard fields by means of DAOPHOT II package (Stetson 1987(Stetson , 1991.…”

Section: Photometric Calibrationmentioning

confidence: 99%

Optical multiband surface photometry of a sample of Seyfert galaxies

Slavcheva-Mihova

¹

,

Mihov

²

2010

A&A

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Context. Parallel analysis of the large-scale morphology and local environment of matched active and control galaxy samples plays an important role in studies of the fueling of active galactic nuclei. Aims. We carry out a detailed morphological characterization of a sample of 35 Seyfert galaxies and a matched sample of inactive galaxies in order to compare the evidence of non-axisymmetric perturbation of the potential and, in the second part of this paper, to be able to perform a multicomponent photometric decomposition of the Seyfert galaxies. Methods. We constructed contour maps, BVR C I C profiles of the surface brightness, ellipticity, and position angle, as well as colour index profiles. We further used colour index images, residual images, and structure maps, which helped clarify the morphology of the galaxies. We studied the presence of close companions using literature data. Results. By straightening out the morphological status of some of the objects, we derived an improved morphological classification and built a solid basis for a further multicomponent decomposition of the Seyfert sample. We report hitherto undetected (to our knowledge) structural components in some Seyfert galaxies -a bar (Ark 479), an oval/lens (Mrk 595), rings (Ark 120, Mrk 376), a nuclear bar and ring (Mrk 352), and nuclear dust lanes (Mrk 590). We compared the large-scale morphology and local environment of the Seyfert sample to those of the control one and found that (1) the two samples show similar incidences of bars, rings, asymmetries, and close companions; (2) the Seyfert bars are generally weaker than the bars of the control galaxies; (3) the bulk of the two samples shows morphological evidence of non-axisymmetric perturbations of the potential or close companions; (4) the fueling of Seyfert nuclei is not directly related to the large-scale morphology and local environment of their host galaxies.

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“…If the Li  line was stronger than the Ca  line, we classified the star as Li-rich. Soderblom et al (1993) measured the equivalent width of the Li  (W(Li)) and the Ca  magnitudes are given in Petrov et al (2001). The error of the photometry is ±0.04 mag.…”

Section: Optical Spectroscopic Observationmentioning

confidence: 99%

Search for new T Tauri stars in the Cepheus-Cassiopeia region

Tachihara¹,

Neuhäuser²,

Kun

³

et al. 2005

A&A

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Abstract. The Cepheus-Cassiopeia star-forming region has been searched for new T Tauri stars (TTSs) based on the ROSAT all sky survey (RASS). Optical spectroscopic observations were carried out toward 45 GSC stellar counterparts of RASS sources looking for the Li absorption line (6708 Å), a sign of youth. The detection of this line resulted in finding 11 to 16 new TTSs in this region. Using follow-up optical photometric observations and evolutionary models these Li-rich stars are revealed to be young low-mass stars. The most of the young stars are separated from the 13 CO molecular clouds by ∼10 pc, significantly more than in Chamaeleon. A group of the new TTSs are isolated from the CO clouds and distributed inside the previously determined CO void. Possible formation scenarios including the interaction with the supernova shock for the isolated TTSs are discussed.Key words. ISM: clouds -ISM: molecules -stars: formation -stars: late-type -stars: pre-main sequence -X-rays: stars Introduction: The Cepheus-Cassiopeia star-forming regionLarge-scale X-ray surveys are a powerful method to search for T Tauri stars (TTSs) that are widely spread over starforming regions (SFRs). Spectroscopic follow-up observations towards the X-ray sources found by the ROSAT X-ray satellite have been carried out in nearby SFRs such as Taurus ), Chamaeleon (Alcalá et al. 1995), and Lupus (Wichmann et al. 1997, most of which are thought to belong to the Gould belt. These surveys found a large number of T Tauri stars (see Neuhäuser 1997 for a review). One of the interesting results of the X-ray selected TTS surveys is that a large number of TTSs have been found far away from the molecular clouds. Because of their youth ( < ∼ a few ×10 7 yr), they are supposed to be distributed within ∼10 pc of their birthplaces. Nonetheless, many so-called "isolated TTSs", separated from the molecular clouds by more than a few tens of pc, are found, for example, south of the Taurus and η Cha clusters (Mamajek et al. 1999), even though many of those south of Taurus were later reported to be active binaries (Torres et al. 2002). Recent studies suggest that such isolation is likely caused by in situ star formation in small clouds and their subsequent rapid dissipation (e.g., Mizuno et al. 1998;Tachihara et al. 2001).Cepheus-Cassiopeia (Cep-Cas) is a nearby SFR located at l ∼ 100 • -140 • and b ∼ 5 • -25 • . The region has been surveyed extensively for molecular clouds in 12 CO by Grenier et al. (1989) who found a total molecular mass of ∼10 5 M . They reported that the cloud distribution shows a CO void which contains an excess of soft X-rays and radio continuum, suggesting a hot bubble created by a supernova. A distance estimation to several dark clouds have been carried out by measuring the colour excess or utilizing star counts (Kun & Prusti 1993;Kun et al. 1994;Kun 1998;Obayashi et al. 1998). Yonekura et al. (1997) surveyed the region in 13 CO and detected 188 distinct molecular clouds. They obtained different radial velocities suggesting that layers at d...

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“…The nights of photometric quality were calibrated using multi-star standard fields established in stellar clusters. We used the clusters M 92 3 (Majewski et al 1994), NGC 7790 (Odewahn et al 1992;Petrov et al 2001), and M 67 (Chevalier & Ilovaisky 1991) for this purpose.…”

Section: Photometric Calibrationmentioning

confidence: 99%

Optical multiband surface photometry of a sample of Seyfert galaxies. I. Large-scale morphology and local environment analysis of matched Seyfert and inactive galaxy samples

Slavcheva-Mihova,

Mihov

2010

Preprint

0

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Context. Parallel analysis of the large-scale morphology and local environment of matched active and control galaxy samples plays an important role in studies of the fueling of active galactic nuclei. Aims. We carry out a detailed morphological characterization of a sample of 35 Seyfert galaxies and a matched sample of inactive galaxies in order to compare the evidence of non-axisymmetric perturbation of the potential and, in the second part of this paper, to be able to perform a multicomponent photometric decomposition of the Seyfert galaxies. Methods. We constructed contour maps, BVR C I C profiles of the surface brightness, ellipticity, and position angle, as well as colour index profiles. We further used colour index images, residual images, and structure maps, which helped clarify the morphology of the galaxies. We studied the presence of close companions using literature data. Results. By straightening out the morphological status of some of the objects, we derived an improved morphological classification and built a solid basis for a further multicomponent decomposition of the Seyfert sample. We report hitherto undetected (to our knowledge) structural components in some Seyfert galaxies -a bar (Ark 479), an oval/lens (Mrk 595), rings (Ark 120, Mrk 376), a nuclear bar and ring (Mrk 352), and nuclear dust lanes (Mrk 590). We compared the large-scale morphology and local environment of the Seyfert sample to those of the control one and found that (1) the two samples show similar incidences of bars, rings, asymmetries, and close companions; (2) the Seyfert bars are generally weaker than the bars of the control galaxies; (3) the bulk of the two samples shows morphological evidence of non-axisymmetric perturbations of the potential or close companions; (4) the fueling of Seyfert nuclei is not directly related to the large-scale morphology and local environment of their host galaxies.

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CCD standards for U and I in the open cluster NGC 7790

Cited by 7 publications

References 12 publications

Optical multiband surface photometry of a sample of Seyfert galaxies

Optical multiband surface photometry of a sample of Seyfert galaxies

Search for new T Tauri stars in the Cepheus-Cassiopeia region

Optical multiband surface photometry of a sample of Seyfert galaxies. I. Large-scale morphology and local environment analysis of matched Seyfert and inactive galaxy samples

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