J/A+A/409/115 VLA imaging of IRAS 1 Jy ULIRG sample (Nagar+, 2003)
The AGN content of ultraluminous IR galaxies: High resolution VLA imaging of the IRAS 1 Jy ULIRG sample. Nagar N.M., Wilson A.S., Falcke H., Veilleux S., Maiolino R. <Astron. Astrophys. 409, 115 (2003)> =2003A&A...409..115N
ADC_Keywords: Surveys ; Galaxies, IR ; Active gal. nuclei ; Radio sources Keywords: accretion, accretion disks - galaxies: active - galaxies: jets - radio continuum: galaxies - surveys Abstract: This paper presents the results of a high resolution radio imaging survey of 83 of the 118 ultraluminous infrared galaxies (ULIRGs) in the IRAS 1Jy ULIRG sample (Kim & Sanders, 1998ApJS..119...41K, Veilleux et al., 2002, Cat. J/ApJS/143/315). We have observed these ULIRGs at 15-GHz with the Very Large Array (VLA). We find that ∼75% of Seyferts (both type 1 and 2) and LINERs have radio nuclei which are compact at our 150mas resolution. The detection rate of HII nuclei is significantly lower (32%); the detections among these are preferentially HII+LINER/Seyfert composite nuclei. Among ULIRGs with multiple optical or near-IR nuclei our observations detected only one (or no) nucleus; in these the radio detection is typically towards the brightest near-IR nucleus. The compactness of the radio sources, the higher detection rates in AGN-type nuclei than HII nuclei, the preferential detection of nuclei with unresolved point sources in the near-IR, the low soft X-ray to nuclear radio luminosity ratio (arguing against thermal emission powering the radio nuclei), and the lack of correlation between radio power and Hα luminosity, all support an origin of the detected radio nuclei in AGN related activity. This result is especially interesting for LINER ULIRGs for which signatures of AGNs have often been ambiguous in other wavebands. Such a high incidence of AGN would provide, for the first time, a large sample in which to study the interplay between AGN, starbursts, and galaxy mergers. Description: Results of new 15GHz VLA A-array observations (150mas resolution) of 83 ULIRGs drawn from the IRAS 1Jy ULIRG sample are listed in the table. These include all (67) of the IRAS 1Jy sample with declination >0°, plus an additional 16 ULIRGs from the sample with declination between 0 and -20 degrees. For each target ULIRG, we list the source name, the activity type and class, the position of the radio source(s) from our 15GHz observations, the offset between the 15GHz radio position and that of the near-infrared nucleus (taken from Kim et al. 2002, Cat. J/ApJS/143/277), the peak and total radio flux densities from a gaussian fit to the nuclear radio source, the redshift, the (assumed isotropic) monochromatic radio power, and any comments. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 89 84 New 2cm VLA observations of the IRAS 1Jy ULIRG sample.
See also: II/156 : IRAS Faint Source Catalog, |b|>10, Version 2.0 (Moshir+ 1989) J/ApJS/143/315 : IRAS 1Jy sample of ultraluminous galaxies II. (Veilleux+ 2002) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 11 A11 --- FSC IRAS FSC name (FHHMMm+DDMM or ZHHMMm+DDMM) 12- 13 A2 --- n_FSC Multiplicity index on FSC (1) 15- 17 A3 --- AType Nuclear activity type (2) 19- 20 I2 h RAh ? 15GHz radio right ascension (J2000) 22- 23 I2 min RAm ? 15GHz radio right ascension (J2000) 25- 30 F6.3 s RAs ? 15GHz radio right ascension (J2000) 32 A1 --- DE- ? 15GHz radio declination sign (J2000) 33- 34 I2 deg DEd ? 15GHz radio declination (J2000) 36- 37 I2 arcmin DEm ? 15GHz radio declination (J2000) 39- 43 F5.2 arcsec DEs ? 15GHz radio declination (J2000) 45- 48 F4.2 arcsec Delta ? Offset between the 15GHz radio position and the position of the near-IR nucleus as listed in KVS (Veilleux et al., 2002, Cat. J/ApJS/143/315) 50- 56 F7.1 mJy Speak ? Peak flux density at 15GHz (in mJy/beam) 58 A1 --- l_Stot Limit flag on Stot 59- 65 F7.1 mJy Stot Total flux at 15GHz 67- 71 F5.3 --- z Redshift of the ULIRG from Veilleux et al., 1999, Cat. J/ApJ/522/113 73 A1 --- l_logPcore Limit flag on logPcore 74- 78 F5.2 [W/Hz] logPcore Core radio power at 15GHz 80- 89 A10 --- Com Comments (3)
Note (1): When the radio source is clearly identifiable with one subcomponent of a multi-component ULIRG, then the component (following the naming convention of KVS, J/ApJS/143/315) is also listed. Note (2): Nuclear activity type: L: LINER S: Seyfert H: HII region type spectrum 2: no broad Hα or broad Paα detected 1: broad Hα or broad Paα are detected (Veilleux et al., 1999, Cat. J/ApJ/522/113, 1999ApJ...522..139V) ":" represents an uncertain classification. H II: display spectra which are transitional between H II regions and Seyferts/LINERs Note (3): Comments: 1: phase-calibration not used; the radio position listed is taken from the VLA calibrator database; 2: uncertain detection. Flux measured by summing within an aperture rather than by a Gaussian fit; 3: known to have a milli-arcsec scale radio core (Smith et al., 1998ApJ...492..137S, 1998ApJ...493L..17S); 4: known to have a milli-arcsec scale radio core (Ulvestad et al., 1999ApJ...517L..81U); 5: known to have a milli-arcsec scale radio core; 6: broad Pa (but not broad Hα) is detected in this object, so it is counted as a Seyfert 1 in this paper; 7: the highly accurate radio position (Ma et al., 1998, Cat. I/251) is offset from both near-IR nuclei, but is closer to the "W" nucleus.
Acknowledgements: Neil Nagar
(End) Neil Nagar [Kapteyn Institute], Patricia Bauer [CDS] 16-Sep-2003
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