Explanation of the extragalactic proper motion list.

The data in this list are 224 NGC galaxies¹ and bright quasars² that have entries in the PPMXL³, UCAC4⁴, or URAT1⁵, within 2" of their HNGC positions that have non zero proper motions. The actual proper motions of a galaxy in the ICRS⁶ coordinate system are below current measurement thresholds.

Each entry in the list begins with the NGC galaxy or LBQS quasar name and its visual magnitude, followed by a short table of entries in the astrometric catalogs that are within 2" of the extragalactic object. The data in the table's column gives:

1. δ) The distance from the extragalactic object to the catalog object in arc seconds.
2. J2000) The J2000 coordinates for the astrometric catalog object.
3. mv) The catalog's visual magnitude, Johnson V band or G band (Gaia).
4. PM Ra) The proper motion in right ascension, in milliarcseconds/year.
5. PM Dec) The proper motion in declination, in milliarcseconds/year.
6. Id) The astrometric catalog identification number for the object.
7. Cat) The astrometric catalog code. P: PPMXL, U: UCAC4, Z: URAT1.

Notes:

• A magnitude of 30 means there was no magnitude data for this object.
• The Tycho⁷ and Gaia⁸ catalogs were also searched, but no anomalies were found in either of them.
• That a star in the Gaia catalog was included in this study only if it had a measured proper motion. This eliminated the vast majority of the Gaia stars.

Method

The catalogs were downloaded from their respective sites, and separate C programs were written to parse the data into this format:

typedef struct StarData {
  double ra;    // J 2000 Right ascension in radians.
  double dec;   // J 2000 Declination in radians.
  int mv;       // Visual magnitude. * 100. 3000 == no data.
  int mb;       // blue magnitude. * 100. 3000 == no data.
  int mk;       // K band magnitude. * 100. 3000 == no data.
  int pmRa;     // Proper motion in RA in mas/yr. * 100.
  int pmDec;    // Proper motion in dec in mas/yr. * 100.
  int pme;      // Proper motion error in mas/yr. * 100.
  char cat;     // Catalog the data is from.
  char id[23];  // Catalog ID.
} sData; 

Coordinates were precessed to J 2000 if necessary.

Each catalog's dataset was then combined into a master dataset, sorted by right ascension.

The master dataset was then parsed, object by object. When a quasar or galaxy was found, all objects within 2" of it were examined. If these were found to have proper motions greater than zero, the galaxy or quaser was included in the list, along with the objects within 2" of it

References

1) The Historically Corrected New General Catalogue

2) LBQS: The Large Bright Quasar Survey

3) The PPMXL catalog web site.

4) The Fourth US Naval Observatory CCD Astrographic Catalog (UCAC4). Zacharias, et al, 2012.

5) The extragalactic reference system of the International Earth Rotation Service, ICRS. Arias et al.

6) The URAT web site

7) The Tycho catalog web site.

8) The Gaia Data Release 1 web site.