The Chandra Multiwavelength Project:Galactic Plane Survey Chandra X-ray Observatory National Optical Astronomy Observatory

The ChaMPlane survey is being conducted at the Harvard-Smithsonian Center for Astrophysics.

Bulge Latitude Survey

The ChaMPlane team is conducting a "Bulge Latitude Survey" (BLS) to measure the latitude distribution of faint X-ray point sources in the region b = +/- 1.5°, l = +/- 0.35° centered at l = 0°. The science goals closely connect to those of our ChaMPlane survey, with the focus on measuring the large-scale distribution — and hence the nature! — of the low-luminosity (LX ≤ 1033erg s-1) point-source population away from the Galactic Center. Therefore, this survey directly complements the previous survey of Wang et al. (2002) for the longitude distribution of sources in the central Bulge, but also our deep Bulge Windows Survey of low-extinction regions between 1.5° and 4° from the Galactic Center.

Survey coverage
The BLS is proposed to ultimately be 36 ACIS-I pointings of 15 ks each above/below the plane at the Galactic Center. In Chandra cycle 7, two-thirds of the region below the galactic plane were observed (BLS-Sa); observations of a similar-sized region above the plane (BLS-Na) are planned for cycle 8 (summer 2007). For cycle 9, we proposed to complete the full area of the survey (BLS-Sb and BLS-Nb). This image shows the regions of the BLS survey in relation to those of the Wang survey, and our Windows survey (inset). The green contours in the inset follow the visual extinction AV, going from about AV=1.6 in Baade's Window to AV ≥ 30 in the Galactic Center. (click image to enlarge)

First results
This image shows the first results of the BLS: the X-ray (left) and ISPI near-infrared (right) images of BLS-Sa (covering b = -0.2 to -1.5° and l = -0.35 to +0.25°) are shown on the same scale and at the same orientation. Color images were created by coding RGB channels as follows: 0.3-2 keV, 2-4 keV, 4-8 keV for the X-ray and K (2.2 μ), H (1.6 μ), J (1.2 μ) for the near-infrared image. Hard X-ray sources in the Bulge appear blue-ish (left). Moving down in galactic latitude, diffuse soft emission (red) becomes visible. In the infrared image, the extinction and dense molecular clouds thin out over the same distance, hence the higher star density and bluer appearance in this direction. The infrared coverage is incomplete as a result of time lost due to bad weather. (click image to enlarge)
Mosaiced Chandra (0.3-8 keV) BLS-Sa image (left) and partially completed mosaiced CTIO ISPI (J,H,K) BLS-Sa image (right). BLS-Na is scheduled for July 2007, and the remaining ISPI coverage will be obtained then for BLS-Sa as well. Completion of the full survey is proposed for Chandra Cycle 9 with BLS-Sb/Nb and corresponding ISPI coverage for IR.