Table information for 'cars.srccat'

General

Table Description: Extracted sources from the CARS survey, comprising positions and multiband photometry.

This table is available for ADQL queries and through the TAP endpoint.

Resource Description: Images and data from from the CFHTLS archive research survey, a multi-band dataset spanning 37 square degrees of sky in high galactic latitudes.

For a list of all services and tables belonging to this table's resource, see Information on resource 'CARS survey data'

Citing this table

This table has an associated publication. If you use data from it, it may be appropriate to reference 2009A&A...493.1197E (ADS BibTeX entry for the publication) either in addition to or instead of the service reference.

To cite the table as such, we suggest the following BibTeX entry:

@MISC{vo:cars_srccat,
  year=2009,
  title={{CARS} survey data},
  author={Erben, T. and Hildebrandt, H. and Lerchster, M. and Hudelot, P. and Benjamin, J. and van Waerbeke, L. and Schrabback, T. and Brimioulle, F. and Cordes, O. and Dietrich, J. P. and Holhjem, K. and Schirmer, M. and Schneider, P.},
  url={http://dc.zah.uni-heidelberg.de/tableinfo/cars.srccat},
  howpublished={{VO} resource provided by the {GAVO} Data Center}
}

Copyright, License, Acknowledgements

If you use the CARS products for your own research, please give proper acknowledgment to CADC, the CFHTLS project and the publication 2009A&A...493.1197E

Resource Documentation

These services deliver products from the CFHTLS-Archive-Research Survey (CARS). The survey currently offers derived products from 37 sq. degrees of the Wide part from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). The main documentation for the products, its creation and its content is the publication 2009A&A...493.1197E. Here, we discuss some points which are not evident from this publication.

AVAILABLE DATA PRODUCTS

For each 1 sq. deg. CARS pointing we currently offer the following products (we discuss them on the example of the CARS pointing W1m0p1); a typical file is named W1m0p1_izrgu.V1.7A.final.cat. The name contains the following information:

W1m0p1 -- name of CARS field under consideration
izrgu -- filters involved in the product (here i', r', z', g', u*); for catalogues etc. the first listed filter corresponds to the object detection filter (here 'i'; see also 2009A&A...493.1197E)
V1.7A -- internal CARS version number
final -- 'final' product

The individual files we offer are:

W1m0p1_izrgu.V1.7A.final.cat

object catalogue in FITS binary format; beware that they are very big and cumbersome to handle if you do not have efficient tools to work on big FITS binary tables! (typical file size per field: 0.5GB!)

W1m0p1_izrgu.V1.7A.final.asc.gz

An ASCII version of W1m0p1_izrgu.V1.7A.final.cat containing a subset of the most important catalogue quantities. This catalogue should be sufficient for most users. The main content of the catalogue can also be queried in the cat service. (typical gzipped file size per field: 20MB)

W1m0p1_izrgu.V1.7A.final.reg.gz

An ASCII ds9 region file containing saoimage/ds9 polygon entries (in pixel coordinates). They represent the CARS image masks described in Sect. 3.4 of 2009A&A...493.1197E. Polygons originating from different masking procedures are encoded with different colours (look at expressions such as '# color=yellow' at the end of each line). We offer this file so that interested users can construct own masks containing only parts of our global MASK key. (typical gzipped file size per field: 1MB)

The colour coding in these files is as follows:

yellow: masks from our object density analysis and stars identified in the USNO-A2 catalogue
green: stars identified in the GSC1 and GSC2 cataogues
magenta: masks around extended haloes of bright stars
red: masks from our asteroid track analysis

W1m0p1_irg.V1.7A.truecol.jpg

low resolution true colour i', r' and g' JPG image of the CARS field. These images allow a quick look at the data but they are probably not suitable for high-quality poster print-outs. (typical file size per field: 10MB)

W1m0p1_izrgu.V1.7A.masks.obj.jpg

low resolution JPG image showing object positions and object masks overlayed on the i'-band image. It allows a quick-look at field-layout and object positions. (typical file size per field: 3MB)

The colour coding in this is:

green: areas excluded from scientific analysis by our MASK key
yellow: stellar sources (SExtractor CLASS_STAR >=0.95)
red: galaxies with high-confidence photo-z estimates: (SExtractor CLASS_STAR < 0.95; reliable object photometry in five bands; BPZ ODDS quality parameter > 0.9); see also Sect. 4 of 2009A&A...493.1197E
blue: all other galaxies (SExtractor CLASS_STAR < 0.95)

CATALOGUE QUANTITIES

See 2009A&A...493.1197E, in particular Sect. 4, and the SExtractor Users manual for a description of most catalogue entries. Also see the table notes.

CURRENT COVERAGE

Columns

Sorted by DB column index. [Sort alphabetically]

Name	Table Head	Description	Unit	UCD
carsid	Id	CARS object ID	N/A	meta.id;meta.main
SeqNr	No	Running object number (in field)	N/A	meta.id
raj2000	RA	Right ascension of barycenter (J2000)	deg	pos.eq.ra;meta.main
dej2000	Dec	Declination of barycenter (J2000)	deg	pos.eq.dec;meta.main
xpos	X	Object position on exposure along x	pix	pos.cartesian.x;instr.det
ypos	Y	Object position on exposure along y	pix	pos.cartesian.y;instr.det
magAuto	Auto. mag.	Kron-like elliptical aperture magnitude [Note 1]	mag	phot.mag
magErrAuto	Err. Auto. mag.	Error in Kron-like elliptical aperture magnitude	mag	stat.error;phot.mag
magisoU	Iso. mag. u*	Isophotal magnitude in the u* band [Note 1]	mag	phot.mag;em.opt
magisoErrU	Err. iso. mag. u*	RMS error of isophotal magnitude in the u* band	mag	stat.error;phot.mag;em.opt
magaprU	F.a. mag. u*	Fixed aperture magnitude in the u* band [Note 1]	mag	phot.mag;em.opt
magaprErrU	Err. F.a. mag. u*	RMS error of fixed aperture magnitude in the u* band	mag	stat.error;phot.mag;em.opt
maglimU	Lim. mag. u*	Limiting magnitude at object's position in u* band [Note 4]	mag	N/A
magisoG	Iso. mag. g'	Isophotal magnitude in the g' band [Note 1]	mag	phot.mag;em.opt
magisoErrG	Err. iso. mag. g'	RMS error of isophotal magnitude in the g' band	mag	stat.error;phot.mag;em.opt
magaprG	F.a. mag. g'	Fixed aperture magnitude in the g' band [Note 1]	mag	phot.mag;em.opt
magaprErrG	Err. F.a. mag. g'	RMS error of fixed aperture magnitude in the g' band	mag	stat.error;phot.mag;em.opt
maglimG	Lim. mag. g'	Limiting magnitude at object's position in g' band [Note 4]	mag	N/A
magisoR	Iso. mag. r'	Isophotal magnitude in the r' band [Note 1]	mag	phot.mag;em.opt
magisoErrR	Err. iso. mag. r'	RMS error of isophotal magnitude in the r' band	mag	stat.error;phot.mag;em.opt
magaprR	F.a. mag. r'	Fixed aperture magnitude in the r' band [Note 1]	mag	phot.mag;em.opt
magaprErrR	Err. F.a. mag. r'	RMS error of fixed aperture magnitude in the r' band	mag	stat.error;phot.mag;em.opt
maglimR	Lim. mag. r'	Limiting magnitude at object's position in r' band [Note 4]	mag	N/A
magisoI	Iso. mag. i'	Isophotal magnitude in the i' band [Note 1]	mag	phot.mag;em.opt
magisoErrI	Err. iso. mag. i'	RMS error of isophotal magnitude in the i' band	mag	stat.error;phot.mag;em.opt
magaprI	F.a. mag. i'	Fixed aperture magnitude in the i' band [Note 1]	mag	phot.mag;em.opt
magaprErrI	Err. F.a. mag. i'	RMS error of fixed aperture magnitude in the i' band	mag	stat.error;phot.mag;em.opt
maglimI	Lim. mag. i'	Limiting magnitude at object's position in i' band [Note 4]	mag	N/A
magisoZ	Iso. mag. z'	Isophotal magnitude in the z' band [Note 1]	mag	phot.mag;em.opt
magisoErrZ	Err. iso. mag. z'	RMS error of isophotal magnitude in the z' band	mag	stat.error;phot.mag;em.opt
magaprZ	F.a. mag. z'	Fixed aperture magnitude in the z' band [Note 1]	mag	phot.mag;em.opt
magaprErrZ	Err. F.a. mag. z'	RMS error of fixed aperture magnitude in the z' band	mag	stat.error;phot.mag;em.opt
maglimZ	Lim. mag. z'	Limiting magnitude at object's position in z' band [Note 4]	mag	N/A
fwhm	FWHM	Full width half max assuming a gaussian core	deg	phys.angSize
fluxRadius	Flux rad.	Fraction-of-light radius	pix	N/A
majorAxis	RMS major	Profile RMS along major axis	deg	phys.angSize.smajAxis
minorAxis	RMS minor	Profile RMS along minor axis	deg	phys.angSize.sminAxis
theta	Pos. Ang.	Position angle (east of north) (J2000)	deg	pos.posAng
sgclass	S/G	S/G classifier output (0..1)	N/A	src.class.starGalaxy
extflags	Ext. Flags	Extraction Flags	N/A	N/A
mask	In mask	True if object is within an object mask	N/A	meta.code
z_b	Z_B	Photometric redshift	N/A	N/A
t_b	T_B	Mask value	N/A	N/A
odds	z odds	Confidence parameter for photometric redshift	N/A	N/A
NgoodFilters	#Good	Number of filters with good photometry for BPZ [Note 2]	N/A	meta.code.qual
NbadFilters	#Bad	Number of filters with bad photometry for BPZ [Note 2]	N/A	meta.code.qual
NfaintFilters	#Faint	Number of filters with faint photometry for BPZ [Note 2]	N/A	meta.code.qual
goodFilters	Good	Filters with faint photometry for BPZ [Note 3]	N/A	N/A
badFilters	Bad	Filters with bad photometry for BPZ [Note 3]	N/A	N/A
faintFilters	Faint	Filters with faint photometry for BPZ [Note 3]	N/A	N/A
fieldKey	Field	CARS field designation	N/A	meta.id

Columns that are parts of indices are marked like this.

Other

The following services may use the data contained in this table:

VOResource

VO nerds may sometimes need VOResource XML for this table.

Notes

Note 1
The fluxes and related quantities are the result of a statistical analysis that may yield three different results, viz.,
- invalid measurement: value and error are both NULL
- null detection (i.e., we are sure that nothing has been detected down to
  
  the local limit): value 99, error NULL
- object detection: value anything but 99, valid error
This means that something like:
```
SELECT sum(magisoU)/count(*) FROM cars.srccat WHERE <whatever>
```
to estimate a mean magnitude will, in all likelihood, not give the correct result since values of 99 will be present in the sum.

Instead, use something like:
```
SELECT sum(magisoU)/count(*) FROM cars.srccat
        WHERE magisoErrU IS NOT NULL
        AND <whatever>
```
Note 2
The relation between NgoodFilters/NBPZ_GOODFILT, NbadFilters/NBPZ_BADFILT, NfaintFilters/NBPZ_LIMFILT is as follows:

The number of filters in which an object has 'reliable photometry' is given NgoodFilters. Reliable photometry means magnitude errors < 1 mag and an object brighter than the limiting magnitude.

NbadFilters is the number of filters in which an object has formal magnitude errors of 1 mag or larger.

NfaintFilters is the number of filters in which an object is fainter than the formal limiting magnitude.

If an object would fall into badFilters AND faintFilters it is listed under badFilters. Magnitude errors refer to isophotal magnitudes; the adopted limiting magnitude is defined in Sect. 2 of 2009A&A...493.1197E.
Note 3
For the meaning of good, bad, and faint, see note 2.

The goodFilters/BPZ_GOODFILT, badFilters/BPZ_BADFILT, and failtFilters/BPZ_LIMFILT columns contain a binary encoding of the filters:

Filter Bit Value

The columns contain the sum of the values of the filters fulfilling the corresponding criteria.
Note 4
For non-detected objects in a filter magnitude limit columns might contain an invalid value NaN (NULL in the database).

Metadata

Identifier

Cite this

Description

Keywords

Creator

Created

Data updated

Metadata updated

Rights

Source

Reference URL