Deep galaxy counts in the K band with the Keck telescope

S. Djorgovski, B. T. Soifer, M. A. Pahre, J. E. Larkin, J. D. Smith, G. Neugebauer, I. Smail, K. Matthews, D. W. Hogg, R. D. Blandford, J. Cohen, W. Harrison, J. Nelson

    Research output: Contribution to journalArticle

    Abstract

    We present deep galaxy counts in the K (λ2.2 μm) band, obtained at the W. M. Keck 10 m telescope. The data reach limiting magnitudes K ∼ 24 mag, about 5 times deeper than the deepest published K-band images to date. The counts are performed in three small (∼1′), widely separated high-latitude fields. Extensive Monte Carlo tests were used to derive the completeness corrections and minimize photometric biases. The counts continue to rise, with no sign of a turnover, down to the limits of our data, with the logarithmic slope of d log N/dm = 0.315 ± 0.02 between K = 20 and 24 mag. This implies a cumulative surface density of ∼5 × 105 galaxies deg-2, or ∼2 × 1010 over the entire sky, down to K = 24 mag. Our counts are in good agreement with, although slightly lower than, those from the Hawaii Deep Survey by Cowie and collaborators; the discrepancies may be due to the small differences in the aperture corrections. The observed field-to-field variations are as expected from the Poissonian noise and galaxy clustering as described by the angular two-point correlation function for faint galaxies. We compare our counts with some of the available theoretical predictions. The data do not require models with a high value of Ω0, but can be well fitted by models with no (or little) evolution, and cosmologies with a low value Ω0. Given the uncertainties in the models, it may be premature to put useful constrains on the value of Ω0 from the counts alone. Optical-to-IR colors are computed, using CCD data obtained previously at Palomar. We find a few red galaxies with (r - K) ≳ 5 mag, or (i - K) ≳ 5 mag; these may be ellipticals at z ∼ 1. While the redshift distribution of galaxies in our counts is still unknown, the flux limits reached would allow us to detect unobscured L* galaxies out to substantial redshifts (z > 3?).

    Original languageEnglish (US)
    JournalAstrophysical Journal
    Volume438
    Issue number1 PART 2
    StatePublished - Jan 1 1995

    Fingerprint

    extremely high frequencies
    telescopes
    galaxies
    turnover
    completeness
    polar regions
    prediction
    sky
    charge coupled devices
    apertures
    slopes
    color
    predictions

    Keywords

    • Cosmology: observations
    • Galaxies: evolution
    • Galaxies: photometry

    ASJC Scopus subject areas

    • Space and Planetary Science

    Cite this

    Djorgovski, S., Soifer, B. T., Pahre, M. A., Larkin, J. E., Smith, J. D., Neugebauer, G., ... Nelson, J. (1995). Deep galaxy counts in the K band with the Keck telescope. Astrophysical Journal, 438(1 PART 2).

    Deep galaxy counts in the K band with the Keck telescope. / Djorgovski, S.; Soifer, B. T.; Pahre, M. A.; Larkin, J. E.; Smith, J. D.; Neugebauer, G.; Smail, I.; Matthews, K.; Hogg, D. W.; Blandford, R. D.; Cohen, J.; Harrison, W.; Nelson, J.

    In: Astrophysical Journal, Vol. 438, No. 1 PART 2, 01.01.1995.

    Research output: Contribution to journalArticle

    Djorgovski, S, Soifer, BT, Pahre, MA, Larkin, JE, Smith, JD, Neugebauer, G, Smail, I, Matthews, K, Hogg, DW, Blandford, RD, Cohen, J, Harrison, W & Nelson, J 1995, 'Deep galaxy counts in the K band with the Keck telescope', Astrophysical Journal, vol. 438, no. 1 PART 2.
    Djorgovski S, Soifer BT, Pahre MA, Larkin JE, Smith JD, Neugebauer G et al. Deep galaxy counts in the K band with the Keck telescope. Astrophysical Journal. 1995 Jan 1;438(1 PART 2).
    Djorgovski, S. ; Soifer, B. T. ; Pahre, M. A. ; Larkin, J. E. ; Smith, J. D. ; Neugebauer, G. ; Smail, I. ; Matthews, K. ; Hogg, D. W. ; Blandford, R. D. ; Cohen, J. ; Harrison, W. ; Nelson, J. / Deep galaxy counts in the K band with the Keck telescope. In: Astrophysical Journal. 1995 ; Vol. 438, No. 1 PART 2.
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    abstract = "We present deep galaxy counts in the K (λ2.2 μm) band, obtained at the W. M. Keck 10 m telescope. The data reach limiting magnitudes K ∼ 24 mag, about 5 times deeper than the deepest published K-band images to date. The counts are performed in three small (∼1′), widely separated high-latitude fields. Extensive Monte Carlo tests were used to derive the completeness corrections and minimize photometric biases. The counts continue to rise, with no sign of a turnover, down to the limits of our data, with the logarithmic slope of d log N/dm = 0.315 ± 0.02 between K = 20 and 24 mag. This implies a cumulative surface density of ∼5 × 105 galaxies deg-2, or ∼2 × 1010 over the entire sky, down to K = 24 mag. Our counts are in good agreement with, although slightly lower than, those from the Hawaii Deep Survey by Cowie and collaborators; the discrepancies may be due to the small differences in the aperture corrections. The observed field-to-field variations are as expected from the Poissonian noise and galaxy clustering as described by the angular two-point correlation function for faint galaxies. We compare our counts with some of the available theoretical predictions. The data do not require models with a high value of Ω0, but can be well fitted by models with no (or little) evolution, and cosmologies with a low value Ω0. Given the uncertainties in the models, it may be premature to put useful constrains on the value of Ω0 from the counts alone. Optical-to-IR colors are computed, using CCD data obtained previously at Palomar. We find a few red galaxies with (r - K) ≳ 5 mag, or (i - K) ≳ 5 mag; these may be ellipticals at z ∼ 1. While the redshift distribution of galaxies in our counts is still unknown, the flux limits reached would allow us to detect unobscured L* galaxies out to substantial redshifts (z > 3?).",
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    T1 - Deep galaxy counts in the K band with the Keck telescope

    AU - Djorgovski, S.

    AU - Soifer, B. T.

    AU - Pahre, M. A.

    AU - Larkin, J. E.

    AU - Smith, J. D.

    AU - Neugebauer, G.

    AU - Smail, I.

    AU - Matthews, K.

    AU - Hogg, D. W.

    AU - Blandford, R. D.

    AU - Cohen, J.

    AU - Harrison, W.

    AU - Nelson, J.

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    N2 - We present deep galaxy counts in the K (λ2.2 μm) band, obtained at the W. M. Keck 10 m telescope. The data reach limiting magnitudes K ∼ 24 mag, about 5 times deeper than the deepest published K-band images to date. The counts are performed in three small (∼1′), widely separated high-latitude fields. Extensive Monte Carlo tests were used to derive the completeness corrections and minimize photometric biases. The counts continue to rise, with no sign of a turnover, down to the limits of our data, with the logarithmic slope of d log N/dm = 0.315 ± 0.02 between K = 20 and 24 mag. This implies a cumulative surface density of ∼5 × 105 galaxies deg-2, or ∼2 × 1010 over the entire sky, down to K = 24 mag. Our counts are in good agreement with, although slightly lower than, those from the Hawaii Deep Survey by Cowie and collaborators; the discrepancies may be due to the small differences in the aperture corrections. The observed field-to-field variations are as expected from the Poissonian noise and galaxy clustering as described by the angular two-point correlation function for faint galaxies. We compare our counts with some of the available theoretical predictions. The data do not require models with a high value of Ω0, but can be well fitted by models with no (or little) evolution, and cosmologies with a low value Ω0. Given the uncertainties in the models, it may be premature to put useful constrains on the value of Ω0 from the counts alone. Optical-to-IR colors are computed, using CCD data obtained previously at Palomar. We find a few red galaxies with (r - K) ≳ 5 mag, or (i - K) ≳ 5 mag; these may be ellipticals at z ∼ 1. While the redshift distribution of galaxies in our counts is still unknown, the flux limits reached would allow us to detect unobscured L* galaxies out to substantial redshifts (z > 3?).

    AB - We present deep galaxy counts in the K (λ2.2 μm) band, obtained at the W. M. Keck 10 m telescope. The data reach limiting magnitudes K ∼ 24 mag, about 5 times deeper than the deepest published K-band images to date. The counts are performed in three small (∼1′), widely separated high-latitude fields. Extensive Monte Carlo tests were used to derive the completeness corrections and minimize photometric biases. The counts continue to rise, with no sign of a turnover, down to the limits of our data, with the logarithmic slope of d log N/dm = 0.315 ± 0.02 between K = 20 and 24 mag. This implies a cumulative surface density of ∼5 × 105 galaxies deg-2, or ∼2 × 1010 over the entire sky, down to K = 24 mag. Our counts are in good agreement with, although slightly lower than, those from the Hawaii Deep Survey by Cowie and collaborators; the discrepancies may be due to the small differences in the aperture corrections. The observed field-to-field variations are as expected from the Poissonian noise and galaxy clustering as described by the angular two-point correlation function for faint galaxies. We compare our counts with some of the available theoretical predictions. The data do not require models with a high value of Ω0, but can be well fitted by models with no (or little) evolution, and cosmologies with a low value Ω0. Given the uncertainties in the models, it may be premature to put useful constrains on the value of Ω0 from the counts alone. Optical-to-IR colors are computed, using CCD data obtained previously at Palomar. We find a few red galaxies with (r - K) ≳ 5 mag, or (i - K) ≳ 5 mag; these may be ellipticals at z ∼ 1. While the redshift distribution of galaxies in our counts is still unknown, the flux limits reached would allow us to detect unobscured L* galaxies out to substantial redshifts (z > 3?).

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