Showing papers by "Stephen E. Schneider published in 2009"

HI line observations of 2MASS galaxies in the Zone of Avoidance

Abstract: A pilot survey has been made to obtain 21cm HI emission line profiles for 197 objects in the Zone of Avoidance (ZoA) that were classified as galaxies in the 2MASS all-sky near-infrared Extended Source Catalog (2MASX) 116 of the sources were observed using the Nancay radio telescope, in the 325 to 11,825 km/s range, and the other 81 sources were observed at Arecibo in the -500 to 11,000 km/s range, and for 9 also in the 9,500 to 21,000 km/s range Global HI line parameters are presented for the 22 and 29 2MASX objects that were detected at Nancay and Arecibo, respectively, as well as upper limits for the undetected 2MASX objects Whereas object 2MASX J08170147-3410277 appears to be a very massive galaxy with an HI mass of 46 x 10E10 Msun, it is clear that only radio synthesis HI imaging observations will allow a firm conclusion on this Overall, the global properties of the detected galaxies match those of other ZoA HI surveys Although the detections are as yet too sparse to give further insight into suspected or unknown large-scale structures in the ZoA, they already indicate that an extension of the present pilot survey is bound to quantify filaments, clusters, and voids behind this part of the Milky Way It is shown that the number of candidate 2MASS-selected ZoA galaxies to be observed in HI could have been reduced by about 15% through examination of composite near-infrared images and the application of extinction-corrected near-infrared colour limits Present results confirm that the Galactic extinction values from Schlegel et al (1998) are valid for latitudes above |b|=5 degrees, but increasingly less so for lower latitudes

H I line observations of 2MASS galaxies in the zone of avoidance

Abstract: Aims: A pilot survey has been made to obtain 21 cm H i emission line profiles for 197 objects in the zone of avoidance (ZoA) that were classified as galaxies in the 2MASS all-sky near-infrared Extended Source Catalog (2MASX), as well as a further 16 2MASS pre-release working database sources that did not make it into 2MASX. Methods: One hundred sixteen of the 2MASX sources and the 16 working database sources were observed using the Nancay radio telescope, usually in the 325 to 11 825 km s-1 range, and the other 81 2MASX sources were observed with the Arecibo radio telescope in the -500 to 11 000 km s-1 range, and for 9 also in the 9500 to 21 000 km s-1 range. Results: Global H i line parameters are presented for the 22 and 29 2MASX objects that were detected at Nancay and Arecibo, respectively, as well as upper limits for the undetected 2MASX objects. Another galaxy (ESO 371-27) was detected in the Nancay beam centred on an undetected target, ESO 371-26. Nancay data on 12 sources could not be used due to high rms noise levels, most likely caused by strong nearby continuum sources. None of the 16 working database sources were detected at Nancay. Whereas object 2MASX J08170147-3410277 appears to be a very massive galaxy with an H i mass of 4.6 × 1010 {M}ȯ and an inclination-corrected rotation velocity of 314 km s-1, it is clear that only radio synthesis H i imaging observations will allow a firm conclusion on this. Conclusions: Overall, the global properties of the detected galaxies match those of other ZoA H i surveys. Although the detections are as yet too sparse to give further insight into suspected or unknown large-scale structures in the ZoA, they already indicate that an extension of the present pilot survey is bound to quantify filaments, clusters, and voids behind this part of the Milky Way. It is shown that the number of candidate 2MASS-selected ZoA galaxies to be observed in H i could have been reduced by about 15% through examination of composite near-infrared images and the application of extinction-corrected near-infrared colour limits. Present results confirm that the Galactic extinction values from Schlegel et al. (1998) are valid for latitudes |b| ⪆ 5°, but increasingly less so for lower latitudes. Tables 1, 2, 4 and 5 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/505/29 Tables 3, 6, 7, and spectra in FITS format are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/505/29

A search for dust emission in the leo intergalactic cloud

Abstract: We present a search for infrared dust emission associated with the Leo cloud, a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared images were obtained with the InfraRed Array Camera and the Multiband Imaging Photometer for Spitzer on the Spitzer Space Telescope. Our analysis of these maps is done at each wavelength relative to the H I spatial distribution. We observe a probable detection at 8 μm and a marginal detection at 24 μm associated with the highest H I column densities in the cloud. At 70 and 160 μm, upper limits on the dust emission are deduced. The level of the detection is low so that the possibility of a fortuitous cirrus clump or of an overdensity of extragalactic sources along the line of sight cannot be excluded. If this detection is confirmed, the quantities of dust inferred imply a dust-to-gas ratio in the intergalactic cloud up to a few times solar but no less than 1/20 solar. A confirmed detection would therefore exclude the possibility that the intergalactic cloud has a primordial origin. Instead, this large intergalactic cloud could therefore have been formed through interactions between galaxies in the group.