arXiv subjects

P. Vaisanen

Publications and source records attributed to P. Vaisanen.

39 records · Page 3Linked to original sources

arXiv2001

Confusion limit due to galaxies: using SIRTF's Infrared Array Camera

Recent ISO-data has allowed for the first time observationally based estimates for source confusion in mid-infrared surveys. We use the extragalactic source counts from ISOCAM in conjunction with K-band counts to predict the confusion due to galaxies in deep mid-IR observations. We specifically concentrate on the near-future Space Infrared Telescope Facility (SIRTF) mission, and calculate expected confusion for the Infrared Array Camera (IRAC) onboard SIRTF. A defining scientific goal of the IRAC instrument will be the study of high redshift galaxies using a deep, confusion limited wide field survey at 3-10 microns. A deep survey can reach 3 $μ$Jy sources with reasonable confidence in the shorter wavelength IRAC bands. Truly confusion limited images at 8 microns will be difficult to obtain due to practical time constraints, unless infrared galaxies exhibit very strong evolution beyond the deepest current observations. We find L^star galaxies to be detectable to z=3-3.5 at 8 microns, which is slightly more pessimistic than found by Simpson & Eisenhardt (1999).

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arXiv2000

Wide-field J- and K-band galaxy counts in the ELAIS fields

New near-infrared galaxy counts in the J and K bands are presented over a total area of 0.70 and 0.97 degrees^2, respectively. The limiting magnitudes of the deepest regions are 19.5 in J and 18.0 in K. At J>16 and K>15 our J and K-band counts number counts agree well with existing surveys provided all data are corrected to a common magnitude scale. There are real differences from field to field, and the ELAIS N1 and N2 fields show an overdensity of J<16, K<15 galaxies. The slopes of log N(m) / dm are 0.40 to 0.45 at 15<K<18 and 16<J<19.5. Our counts favor galaxy models with a high normalization of the local luminosity function and without strong evolution.

astro-ph↗

arXiv1999

The Type Ia Supernova 1998bu in M96 and the Hubble Constant

We present optical and near-infrared photometry and spectroscopy of the type Ia SN 1998bu in the Leo I Group galaxy M96 (NGC 3368). The data set consists of 356 photometric measurements and 29 spectra of SN 1998bu between UT 1998 May 11 and July 15. The well-sampled light curve indicates the supernova reached maximum light in B on UT 1998 May 19.3 (JD 2450952.8 +/- 0.8) with B = 12.22 +/- 0.03 and V = 11.88 +/- 0.02. Application of a revised version of the Multicolor Light Curve Shape (MLCS) method yields an extinction toward the supernova of A_V = 0.94 +/- 0.15 mag, and indicates the supernova was of average luminosity compared to other normal type Ia supernovae. Using the HST Cepheid distance modulus to M96 (Tanvir et al. 1995) and the MLCS fit parameters for the supernova, we derive an extinction-corrected absolute magnitude for SN 1998bu at maximum, M_V = -19.42 +/- 0.22. Our independent results for this supernova are consistent with those of Suntzeff et al. (1999). Combining SN 1998bu with three other well-observed local calibrators and 42 supernovae in the Hubble flow yields a Hubble constant, H_0 = 64^{+8}_{-6} km/s/Mpc, where the error estimate incorporates possible sources of systematic uncertainty including the calibration of the Cepheid period-luminosity relation, the metallicity dependence of the Cepheid distance scale, and the distance to the LMC.

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