Galaxy fields from QORG

Galaxy fields with overdensities of QSOs / QSO candidates.

A selection of interesting fields are presented below. The significance of the QSO/candidate overdensities is unclear, because of the heterogeneity of the source catalogues used by QORG, and the question of what apparent overdensities would be expected randomly. That having been said, these overdensities look significant and are probably largely due to weak lensing about the central galaxy. However, some patterns look oriented along the minor axis of the central galaxy (see the NGC 891 map immediately below for an example), raising the possibility that some of these objects are at the distance of the galaxy, i.e. "intrinsic redshift" objects.

I will say that my own hunt for intrinsic-redshift objects at the central-galaxy distance has been akin to chasing ghosts. Sometimes I have reflected that these look like mirages, or Christmas tree lights. So the scenario that weak lensing is the primary agent for these, seems quite fitting. This is a developing area in current cosmology, hotting up just in the past year (2005-06).

On the sky charts below, where objects are labelled with a decimal, e.g. "1.38", the label is the known redshift of that object. If the label is just an integer, it is the percent chance that the object is a QSO as calculated by the QORG catalog (A&A 2004, 427, 387), or by the same technique used on data published subsequent to QORG. Other objects are labelled by name only: PGC# = galaxy without redshift, TYCHO# = bright star, etc. Technical details on the object formulation and selection are here.


NGC 4151, strong clustering around the central galaxy. Closest object is in the disk. A closer look and a listing of objects is here.			NGC 891, an overdensity of objects, partly across the galaxy minor axis. About 10 of these objects have been identified as QSOs or AGNe. A closer look and listing of objects is here.
More galaxy fields with interesting overdensities; each link goes to its own page with a sky chart(s) and listing of objects: NGC 253 - spray of objects around nearby spiral. NGC 520 - a few objects around this spiral in a sparse sky. NGC 720 - good packing of objects around this elliptical galaxy. NGC 1316 - objects crossing on long and short axes of an S0 galaxy. NGC 1553 - S0 galaxy, presumably prolate, objects seemingly arrayed in arcs along long axis. Also a wide gravitational lens candidate. NGC 3115 - an elliptical galaxy with some high-confidence candidates very close in. NGC 3184 - spiral galaxy with some close-in objects in a dense background. NGC 3227 - objects loitering around galaxy, but no clear patterns. NGC 4559 - objects close in to spiral, and a bunch to the south. NGC 4697 - an elliptical galaxy with objects strung along its major axis, and bunched around the minor axis. Odd appearance. NGC 5033 - bright radio and X-ray objects strung a degree each way from a spiral. Whirlpool Galaxy - objects curtained around galaxy with some symmetry. NGC 5548 -- bright objects congregating about an S0 galaxy. NGC 7314 - many objects packed close by galaxy, boxey configuration. NGC 7479 - a few close-in objects strung across galaxy in an empty sky.

The Leo Triplet - Three galaxies with QSO surrounds. NGC 3628 is virtually ringed by QSOs/candidates, see here for a presentation. NGC 3627 / 3623 are crossed by a stream of candidates, see here.			Galaxy PGC 2998 (never studied) seems to be puffing out objects as it turns. Object D is a quasar. Details here.