Microlensing optical depth toward the galactic bulge using clump giants from the macho survey

P. Popowski, K. Griest, C. L. Thomas, K. H. Cook, D. P. Bennett, A. C. Becker, D. R. Alves, D. Minniti, A. J. Drake, C. Alcock, R. A. Allsman, T. S. Axelrod, K. C. Freeman, M. Geha, M. J. Lehner, S. L. Marshall, C. A. Nelson, B. A. Peterson, P. J. Quinn, C. W. StubbsW. Sutherland, T. Vandehei, D. Welch

Resultado de la investigación: Article

77 Citas (Scopus)

Resumen

Using 7 yr of MACHO survey data, we present a new determination of the optical depth to microlensing toward the Galactic bulge. We select the sample of 62 microlensing events (60 unique) on clump giant sources and perform a detailed efficiency analysis. We use only the clump giant sources because these are bright bulge stars and are not as strongly affected by blending as other events. Using a subsample of 42 clump events concentrated in an area of 4.5 deg2 with 739,000 clump giant stars, we find τ = 2.17 -0.38+0.47 × 10-6 at (l, b) = (1°.50, -2°.68), somewhat smaller than found in most previous MACHO studies but in excellent agreement with recent theoretical predictions. We also present the optical depth in each of the 19 fields in which we detected events and find limits on optical depth for fields with no events. The errors in optical depth in individual fields are dominated by Poisson noise. We measure optical depth gradients of (1.06 ± 0.71) × 10-6 deg-1 and (0.29 ± 0.43) × 10-6 deg-1 in the Galactic latitude b and longitude l directions, respectively. Finally, we discuss the possibility of anomalous duration distribution of events in the field 104 centered on (l, b) = (3°.11, -3°.01), as well as investigate spatial clustering of events in all fields.

Idioma originalEnglish
Páginas (desde-hasta)879-905
Número de páginas27
PublicaciónAstrophysical Journal
Volumen631
N.º2 I
DOI
EstadoPublished - 1 oct 2005

Huella dactilar

galactic bulge
clumps
optical thickness
optical depth
massive compact halo objects
giant stars
longitude
prediction
stars
gradients
predictions

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

Popowski, P., Griest, K., Thomas, C. L., Cook, K. H., Bennett, D. P., Becker, A. C., ... Welch, D. (2005). Microlensing optical depth toward the galactic bulge using clump giants from the macho survey. Astrophysical Journal, 631(2 I), 879-905. https://doi.org/10.1086/432246
Popowski, P. ; Griest, K. ; Thomas, C. L. ; Cook, K. H. ; Bennett, D. P. ; Becker, A. C. ; Alves, D. R. ; Minniti, D. ; Drake, A. J. ; Alcock, C. ; Allsman, R. A. ; Axelrod, T. S. ; Freeman, K. C. ; Geha, M. ; Lehner, M. J. ; Marshall, S. L. ; Nelson, C. A. ; Peterson, B. A. ; Quinn, P. J. ; Stubbs, C. W. ; Sutherland, W. ; Vandehei, T. ; Welch, D. / Microlensing optical depth toward the galactic bulge using clump giants from the macho survey. En: Astrophysical Journal. 2005 ; Vol. 631, N.º 2 I. pp. 879-905.
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title = "Microlensing optical depth toward the galactic bulge using clump giants from the macho survey",
abstract = "Using 7 yr of MACHO survey data, we present a new determination of the optical depth to microlensing toward the Galactic bulge. We select the sample of 62 microlensing events (60 unique) on clump giant sources and perform a detailed efficiency analysis. We use only the clump giant sources because these are bright bulge stars and are not as strongly affected by blending as other events. Using a subsample of 42 clump events concentrated in an area of 4.5 deg2 with 739,000 clump giant stars, we find τ = 2.17 -0.38+0.47 × 10-6 at (l, b) = (1°.50, -2°.68), somewhat smaller than found in most previous MACHO studies but in excellent agreement with recent theoretical predictions. We also present the optical depth in each of the 19 fields in which we detected events and find limits on optical depth for fields with no events. The errors in optical depth in individual fields are dominated by Poisson noise. We measure optical depth gradients of (1.06 ± 0.71) × 10-6 deg-1 and (0.29 ± 0.43) × 10-6 deg-1 in the Galactic latitude b and longitude l directions, respectively. Finally, we discuss the possibility of anomalous duration distribution of events in the field 104 centered on (l, b) = (3°.11, -3°.01), as well as investigate spatial clustering of events in all fields.",
author = "P. Popowski and K. Griest and Thomas, {C. L.} and Cook, {K. H.} and Bennett, {D. P.} and Becker, {A. C.} and Alves, {D. R.} and D. Minniti and Drake, {A. J.} and C. Alcock and Allsman, {R. A.} and Axelrod, {T. S.} and Freeman, {K. C.} and M. Geha and Lehner, {M. J.} and Marshall, {S. L.} and Nelson, {C. A.} and Peterson, {B. A.} and Quinn, {P. J.} and Stubbs, {C. W.} and W. Sutherland and T. Vandehei and D. Welch",
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Popowski, P, Griest, K, Thomas, CL, Cook, KH, Bennett, DP, Becker, AC, Alves, DR, Minniti, D, Drake, AJ, Alcock, C, Allsman, RA, Axelrod, TS, Freeman, KC, Geha, M, Lehner, MJ, Marshall, SL, Nelson, CA, Peterson, BA, Quinn, PJ, Stubbs, CW, Sutherland, W, Vandehei, T & Welch, D 2005, 'Microlensing optical depth toward the galactic bulge using clump giants from the macho survey', Astrophysical Journal, vol. 631, n.º 2 I, pp. 879-905. https://doi.org/10.1086/432246

Microlensing optical depth toward the galactic bulge using clump giants from the macho survey. / Popowski, P.; Griest, K.; Thomas, C. L.; Cook, K. H.; Bennett, D. P.; Becker, A. C.; Alves, D. R.; Minniti, D.; Drake, A. J.; Alcock, C.; Allsman, R. A.; Axelrod, T. S.; Freeman, K. C.; Geha, M.; Lehner, M. J.; Marshall, S. L.; Nelson, C. A.; Peterson, B. A.; Quinn, P. J.; Stubbs, C. W.; Sutherland, W.; Vandehei, T.; Welch, D.

En: Astrophysical Journal, Vol. 631, N.º 2 I, 01.10.2005, p. 879-905.

Resultado de la investigación: Article

TY - JOUR

T1 - Microlensing optical depth toward the galactic bulge using clump giants from the macho survey

AU - Popowski, P.

AU - Griest, K.

AU - Thomas, C. L.

AU - Cook, K. H.

AU - Bennett, D. P.

AU - Becker, A. C.

AU - Alves, D. R.

AU - Minniti, D.

AU - Drake, A. J.

AU - Alcock, C.

AU - Allsman, R. A.

AU - Axelrod, T. S.

AU - Freeman, K. C.

AU - Geha, M.

AU - Lehner, M. J.

AU - Marshall, S. L.

AU - Nelson, C. A.

AU - Peterson, B. A.

AU - Quinn, P. J.

AU - Stubbs, C. W.

AU - Sutherland, W.

AU - Vandehei, T.

AU - Welch, D.

PY - 2005/10/1

Y1 - 2005/10/1

N2 - Using 7 yr of MACHO survey data, we present a new determination of the optical depth to microlensing toward the Galactic bulge. We select the sample of 62 microlensing events (60 unique) on clump giant sources and perform a detailed efficiency analysis. We use only the clump giant sources because these are bright bulge stars and are not as strongly affected by blending as other events. Using a subsample of 42 clump events concentrated in an area of 4.5 deg2 with 739,000 clump giant stars, we find τ = 2.17 -0.38+0.47 × 10-6 at (l, b) = (1°.50, -2°.68), somewhat smaller than found in most previous MACHO studies but in excellent agreement with recent theoretical predictions. We also present the optical depth in each of the 19 fields in which we detected events and find limits on optical depth for fields with no events. The errors in optical depth in individual fields are dominated by Poisson noise. We measure optical depth gradients of (1.06 ± 0.71) × 10-6 deg-1 and (0.29 ± 0.43) × 10-6 deg-1 in the Galactic latitude b and longitude l directions, respectively. Finally, we discuss the possibility of anomalous duration distribution of events in the field 104 centered on (l, b) = (3°.11, -3°.01), as well as investigate spatial clustering of events in all fields.

AB - Using 7 yr of MACHO survey data, we present a new determination of the optical depth to microlensing toward the Galactic bulge. We select the sample of 62 microlensing events (60 unique) on clump giant sources and perform a detailed efficiency analysis. We use only the clump giant sources because these are bright bulge stars and are not as strongly affected by blending as other events. Using a subsample of 42 clump events concentrated in an area of 4.5 deg2 with 739,000 clump giant stars, we find τ = 2.17 -0.38+0.47 × 10-6 at (l, b) = (1°.50, -2°.68), somewhat smaller than found in most previous MACHO studies but in excellent agreement with recent theoretical predictions. We also present the optical depth in each of the 19 fields in which we detected events and find limits on optical depth for fields with no events. The errors in optical depth in individual fields are dominated by Poisson noise. We measure optical depth gradients of (1.06 ± 0.71) × 10-6 deg-1 and (0.29 ± 0.43) × 10-6 deg-1 in the Galactic latitude b and longitude l directions, respectively. Finally, we discuss the possibility of anomalous duration distribution of events in the field 104 centered on (l, b) = (3°.11, -3°.01), as well as investigate spatial clustering of events in all fields.

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DO - 10.1086/432246

M3 - Article

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JO - Astrophysical Journal

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Popowski P, Griest K, Thomas CL, Cook KH, Bennett DP, Becker AC y otros. Microlensing optical depth toward the galactic bulge using clump giants from the macho survey. Astrophysical Journal. 2005 oct 1;631(2 I):879-905. https://doi.org/10.1086/432246