QUAC: an Atlas-Catalogue of Quasars and BL Lacertae objects

PRESENTATION

Due to the fact that they are the farthest sources from the known Universe,
the Quasars (QSO) and the BL Lacertae objects (BL) are not only the most
important aspects either of the cosmological studies and of the other
studies dedicated to far removed from our own objects, but their studies
have started to excite the curiosity and the interest of a large part of the
amatorial Astronomy. This renewed interest is due to the most advanced
technology placed at the modern amateur astronomer's disposal; this
technology is really different from the technology available 20 years ago.

Nowadays these instruments, equipped with sophisticated CCD cameras, can
easily reached the magnitudes of the historical Palomar Observatory Sky
Survey (POSS), a real myth for entire generations of people keen on
astronomical studies.

We should add that the QSO and BL are optically variables and this
phenomenon has excited many amateur astronomers' curiosity and has
guaranteed them large satisfactions.

It's important to remark that there is the realistic probability that such
an object could have leaved its print image centred somewhere on a galaxy or
on a cluster.

All this makes at least interesting the simple knowledge of the exact
positions of these exotic, celestial objects.

But where are exactly the QSO and the BL and what can we do to identify
them? Their pointed aspect makes them very similar to stars and so it's very
difficult to distinguish these objects from stars. That's why it's necessary
a precise identification.

Sometimes astronomers working in this field publish the maps of the studied
objects only, often using very narrow fields and without worrying about the
quality of reproduction.

In the since now published literature there is not a work which presents
more than 100 - 200 finding charts of these objects (usually they present
10-20 units, sometimes some units less) with well shaped images, while the
available catalogue and lists often contain information and details which
are not really interesting for amateur astronomers.

We have thought to make up for this lack publishing a new work called QUAC
(from QUasar Atlas and Catalogue) which contains homogeneous information,
positions and finding charts.

Information and positions are obtained and calculated consulting various
publications while finding charts are directly obtained from the digitized
POSS plates (for fields of 10'x10'), all in the same scale.

The most brilliant objects are suitable to be visually observed and
sometimes they are observable with photoelectric-photometers.

The "QUAC" will be subjected to revisions either interesting the Catalogue
section, with the presentation of new objects and other information, and the
Atlas section where we project to propose a growing number of finding
charts.


STRUCTURE

The QUAC is divided into two parts: Catalogue and Atlas.

The Catalogue is then divided into two tables (I and II).

Table I is arranged into 19 columns containing the following informations:

1: type of the object. At the end of the column there are explanatory notes
and symbols. If there is the celestial colour it means that the map is
available on the Atlas.

2: names mainly known to identify the objects. To see the meaning of various
acronyms and abbreviations, see table II.

3-4-5: right ascension for the equinoxe J2000,0.

6-7-8: declination for the equinoxe J2000,0.

9: red-shift (z).

10: magnitude, usually in V, but see also other indications.

11: B-V colour index.

12: U-B colour index.

13: references to other known publications where it is possible to get an
identification map. The acronym QUAC means that the finding chart of the
object is available in the Atlas section.

14-15-16: right ascension for the equinoxe B1950,0.

17-18-19: declination for the equinoxe B1950,0.

Information between brackets means that we are not certain about
attribution.

Note to the Table I:
QUAC is an instrument subjected to continuous revisions, especially
regarding recently discovered objects. That's why some columns may not
present much information which will be included as soon as they are
available.
The asterisk means references to the compilation of catalogue but these are
not influential for consultation.


Table II regards explanation of the abbreviations and the acronyms usually
used in literature to indicate individual objects. This table is arranged
into five columns:

1: acronym or abbreviation.

2: extensive denomination.

3: spectral band utilized.

4: type of objects presented in the correlated publication.

5: publication containing the catalogue or the referencing list or at least
the essential information the acronym is related to.

A short list of the abbreviations used in periodic and internationally wide
circulation journals follow.


The Atlas is divided into 24 sections (one for each hour of R.A.); within
each section it is possible to trace back to the maps identifying the
objects according to their J2000.0 equatorial co-ordinates.

Substantially there has been the preparation of negative, in GIF
format-file, referring to celestial field having all the same 10'x10'
extensions, with the north at the upper position and the east on the left.

The QUAC, dated March 2003, is now at its second version, while the third
version is now being prepared.

It is possible to download the QUAC from www.vialattea.net/sharru



Rinaldo Monella
SHARRU Astronomical Observatory
Via Giovanni XXIII; 13
24050 COVO BG
Italy

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