### Abstract

We present the first results of the measurements of angular auto-correlation functions (ACFs) of X-ray point sources detected in the XMM-Newton observations of the ∼2 deg ^{2} COSMOS field (COSMOS XMM-Newton). Significant positive signals have been detected in the 0.5-2 (SFT) band, in the angle range of 0.5′-24′, while the positive signals were at the ∼2 and ∼3 σ levels in the 2-4.5 (MED) and 4.5-10 (UHD) keV bands, respectively. Correctly taking integral constraints into account is a major limitation in interpreting our results. With power-law fits to the ACFs without the integral constraint term, we find correlation lengths of θ _{c} = 1.9″ ± 0.3″ , 0.8″ _{-0.4″} ^{+0.5″} and 6″ ± 2″ for the SFT, MED, and UHD bands, respectively, for γ = 1.8. The inferred comoving correlation lengths, also taking into account the bias by the source merging due to XMM-Newton PSF, are r _{c} ≈ 9.8 ± 0.7, 5.8 _{-1.7} ^{+1.4}, and 12 ± 2 h ^{-1} Mpc at the effective redshifts of z̄ _{eff} ≈1.1, 0.9, and 0.6 for the SFT, MED, and UHD bands, respectively. If we include the integral constraint term in the fitting process, assuming that the power law extends to the scale length of the entire COSMOS XMM-Newton field, the correlation lengths become larger by ∼20%-90%. Comparing the inferred rms fluctuations of the spatial distribution of AGNs σ _{8,AGN} with those of the underlying mass, the bias parameters of the X-ray source clustering at these effective redshifts are in the range b _{AGN} = 1.5-4.

Original language | English (US) |
---|---|

Pages (from-to) | 396-405 |

Number of pages | 10 |

Journal | Astrophysical Journal, Supplement Series |

Volume | 172 |

Issue number | 1 |

DOIs | |

State | Published - Oct 22 2007 |

Externally published | Yes |

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### Keywords

- Galaxies: active
- Quasars: general
- X-rays: galaxies

### ASJC Scopus subject areas

- Space and Planetary Science

### Cite this

*Astrophysical Journal, Supplement Series*,

*172*(1), 396-405. https://doi.org/10.1086/516579

**The XMM-Newton wide-field survey in the COSMOS field. V angular clustering of the X-ray point sources.** / Miyaji, Takamitsu; Zamorani, Giovanni; Cappelluti, Nico; Gilli, Roberto; Griffiths, Richard E.; Comastri, Andrea; Hasinger, Günther; Brusa, Marcella; Fiore, Fabrizio; Puccetti, Simonetta; Guzzo, Luigi; Finoguenov, Alexis.

Research output: Contribution to journal › Review article

*Astrophysical Journal, Supplement Series*, vol. 172, no. 1, pp. 396-405. https://doi.org/10.1086/516579

}

TY - JOUR

T1 - The XMM-Newton wide-field survey in the COSMOS field. V angular clustering of the X-ray point sources

AU - Miyaji, Takamitsu

AU - Zamorani, Giovanni

AU - Cappelluti, Nico

AU - Gilli, Roberto

AU - Griffiths, Richard E.

AU - Comastri, Andrea

AU - Hasinger, Günther

AU - Brusa, Marcella

AU - Fiore, Fabrizio

AU - Puccetti, Simonetta

AU - Guzzo, Luigi

AU - Finoguenov, Alexis

PY - 2007/10/22

Y1 - 2007/10/22

N2 - We present the first results of the measurements of angular auto-correlation functions (ACFs) of X-ray point sources detected in the XMM-Newton observations of the ∼2 deg 2 COSMOS field (COSMOS XMM-Newton). Significant positive signals have been detected in the 0.5-2 (SFT) band, in the angle range of 0.5′-24′, while the positive signals were at the ∼2 and ∼3 σ levels in the 2-4.5 (MED) and 4.5-10 (UHD) keV bands, respectively. Correctly taking integral constraints into account is a major limitation in interpreting our results. With power-law fits to the ACFs without the integral constraint term, we find correlation lengths of θ c = 1.9″ ± 0.3″ , 0.8″ -0.4″ +0.5″ and 6″ ± 2″ for the SFT, MED, and UHD bands, respectively, for γ = 1.8. The inferred comoving correlation lengths, also taking into account the bias by the source merging due to XMM-Newton PSF, are r c ≈ 9.8 ± 0.7, 5.8 -1.7 +1.4, and 12 ± 2 h -1 Mpc at the effective redshifts of z̄ eff ≈1.1, 0.9, and 0.6 for the SFT, MED, and UHD bands, respectively. If we include the integral constraint term in the fitting process, assuming that the power law extends to the scale length of the entire COSMOS XMM-Newton field, the correlation lengths become larger by ∼20%-90%. Comparing the inferred rms fluctuations of the spatial distribution of AGNs σ 8,AGN with those of the underlying mass, the bias parameters of the X-ray source clustering at these effective redshifts are in the range b AGN = 1.5-4.

AB - We present the first results of the measurements of angular auto-correlation functions (ACFs) of X-ray point sources detected in the XMM-Newton observations of the ∼2 deg 2 COSMOS field (COSMOS XMM-Newton). Significant positive signals have been detected in the 0.5-2 (SFT) band, in the angle range of 0.5′-24′, while the positive signals were at the ∼2 and ∼3 σ levels in the 2-4.5 (MED) and 4.5-10 (UHD) keV bands, respectively. Correctly taking integral constraints into account is a major limitation in interpreting our results. With power-law fits to the ACFs without the integral constraint term, we find correlation lengths of θ c = 1.9″ ± 0.3″ , 0.8″ -0.4″ +0.5″ and 6″ ± 2″ for the SFT, MED, and UHD bands, respectively, for γ = 1.8. The inferred comoving correlation lengths, also taking into account the bias by the source merging due to XMM-Newton PSF, are r c ≈ 9.8 ± 0.7, 5.8 -1.7 +1.4, and 12 ± 2 h -1 Mpc at the effective redshifts of z̄ eff ≈1.1, 0.9, and 0.6 for the SFT, MED, and UHD bands, respectively. If we include the integral constraint term in the fitting process, assuming that the power law extends to the scale length of the entire COSMOS XMM-Newton field, the correlation lengths become larger by ∼20%-90%. Comparing the inferred rms fluctuations of the spatial distribution of AGNs σ 8,AGN with those of the underlying mass, the bias parameters of the X-ray source clustering at these effective redshifts are in the range b AGN = 1.5-4.

KW - Galaxies: active

KW - Quasars: general

KW - X-rays: galaxies

UR - http://www.scopus.com/inward/record.url?scp=35348893063&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=35348893063&partnerID=8YFLogxK

U2 - 10.1086/516579

DO - 10.1086/516579

M3 - Review article

AN - SCOPUS:35348893063

VL - 172

SP - 396

EP - 405

JO - Astrophysical Journal, Supplement Series

JF - Astrophysical Journal, Supplement Series

SN - 0067-0049

IS - 1

ER -