Key to ASCII object tables

Fld	Strt Col	Ncol	Format	Description
0	0	2	%2d	Run: Data run id number
1	3	1	%1d	Rerun: Data processing id number
2	5	1	%1d	CamCol: Mosaic Camera Column id number
3	7	3	%3d	Field: Run field id number
4	11	4	%4d	Id: Id number within a field
5	16	1	%1d	Type: 3=galaxy, 6=star, 8=sky
6	18	10	%08x	Object Flags: photo pipeline bit flags
7	29	7	%7.2f	Object Column: column number (x) in field
8	37	7	%7.2f	Object Row: row number (y) in field
9	45	10	%10.6f	RA: J2000 RA of object
10	56	10	%10.6f	DEC: J2000 DEC of object
11	67	5	%5.2f	u^* psf magnitude (see note on flux-magnitude system below)
12	73	4	%4.2f	u^* psf magnitude error (see system note)
13	78	5	%5.2f	g^* psf magnitude
14	84	4	%4.2f	g^* psf magnitude error
15	89	5	%5.2f	r^* psf magnitude
16	95	4	%4.2f	r^* psf magnitude error
17	100	5	%5.2f	i^* psf magnitude
18	106	4	%4.2f	i^* psf magnitude error
19	111	5	%5.2f	z^* psf magnitude
20	117	4	%4.2f	z^* psf magnitude error
21	122	5	%5.2f	u^* fiber magnitude
22	128	4	%4.2f	u^* fiber magnitude error
23	133	5	%5.2f	g^* fiber magnitude
24	139	4	%4.2f	g^* fiber magnitude error
25	144	5	%5.2f	r^* fiber magnitude
26	150	4	%4.2f	r^* fiber magnitude error
27	155	5	%5.2f	i^* fiber magnitude
28	161	4	%4.2f	i^* fiber magnitude error
29	166	5	%5.2f	z^* fiber magnitude
30	172	4	%4.2f	z^* fiber magnitude error
31	177	5	%5.2f	u^* Petrosian magnitude
32	183	4	%4.2f	u^* Petrosian magnitude error
33	188	5	%5.2f	g^* Petrosian magnitude
34	194	4	%4.2f	g^* Petrosian magnitude error
35	199	5	%5.2f	r^* Petrosian magnitude
36	205	4	%4.2f	r^* Petrosian magnitude error
37	210	5	%5.2f	i^* Petrosian magnitude
38	216	4	%4.2f	i^* Petrosian magnitude error
39	221	5	%5.2f	z^* Petrosian magnitude
40	227	4	%4.2f	z^* Petrosian magnitude error
41	232	5	%5.2f	u^* Sky Surface Brightness
42	238	5	%5.2f	g^* Sky Surface Brightness
43	244	5	%5.2f	r^* Sky Surface Brightness
44	250	5	%5.2f	i^* Sky Surface Brightness
45	256	5	%5.2f	z^* Sky Surface Brightness
46	263	5	%5.2f	r^* Petrosian Radius (arcsec)
47	268	4	%4.2f	r^* Petrosian Radius error (arcsec)
48	273	6	%6.2f	r^* band Q shape parameter
49	280	6	%6.2f	r^* band U shape parameter
50	287	5	%5.2f	r^* band isophotal elliptical a semi-radius (arcsec)
51	293	5	%5.2f	r^* band isophotal elliptical b semi-radius (arcsec)
52	299	6	%6.1f	r^* band isophotal elliptical inst Position Angle (degrees)
53	306	5	%5.2f	r^* band deVaucouleurs fit scale length (arcsec)
54	312	5	%5.2f	r^* band deVaucouleurs fit elliptical a/b axis ratio
55	318	6	%6.1f	r^* band deVaucouleurs fit elliptical inst Position Angle (degrees)
56	325	5	%5.2f	u^* deVaucouleurs fit magnitude
57	331	5	%5.2f	g^* deVaucouleurs fit magnitude
58	337	5	%5.2f	r^* deVaucouleurs fit magnitude
59	343	5	%5.2f	i^* deVaucouleurs fit magnitude
60	349	5	%5.2f	z^* deVaucouleurs fit magnitude
61	355	5	%5.2f	r^* band exponential disk fit scale length (arcsec)
62	361	5	%5.2f	r^* band exponential disk fit elliptical a/b axis ratio
63	367	6	%6.1f	r^* band exponential disk inst Position Angle (degrees)
64	374	5	%5.2f	u^* exponential disk fit magnitude
65	380	5	%5.2f	g^* exponential disk fit magnitude
66	386	5	%5.2f	r^* exponential disk fit magnitude
67	392	5	%5.2f	i^* exponential disk fit magnitude
68	398	5	%5.2f	z^* exponential disk fit magnitude
69	404	5	%5.2f	u^* best galaxy model fit magnitude
70	410	5	%5.2f	g^* best galaxy model fit magnitude
71	416	5	%5.2f	r^* best galaxy model fit magnitude
72	422	5	%5.2f	i^* best galaxy model fit magnitude
73	428	5	%5.2f	z^* best galaxy model fit magnitude
74	434	5	%5.2f	u^* stellar psf match likelihood
75	440	5	%5.2f	g^* stellar psf match likelihood
76	446	5	%5.2f	r^* stellar psf match likelihood
77	452	5	%5.2f	i^* stellar psf match likelihood
78	458	5	%5.2f	z^* stellar psf match likelihood
79	464	5	%5.2f	u^* exponential disk match likelihood
80	470	5	%5.2f	g^* exponential disk match likelihood
81	476	5	%5.2f	r^* exponential disk match likelihood
82	482	5	%5.2f	i^* exponential disk match likelihood
83	488	5	%5.2f	z^* exponential disk match likelihood
84	494	5	%5.2f	u^* deVauc profile match likelihood
85	500	5	%5.2f	g^* deVauc profile match likelihood
86	506	5	%5.2f	r^* deVauc profile match likelihood
87	512	5	%5.2f	i^* deVauc profile match likelihood
88	518	5	%5.2f	z^* deVauc profile match likelihood
89	524	10	%8x	u^* filter specific object bit flags
90	535	10	%8x	g^* filter specific object bit flags
91	546	10	%8x	r^* filter specific object bit flags
92	557	10	%8x	i^* filter specific object bit flags
93	568	10	%8x	z^* filter specific object bit flags
94	579	2	%2d	u^* filter specific object type
95	582	2	%2d	g^* filter specific object type
96	585	2	%2d	r^* filter specific object type
97	588	2	%2d	i^* filter specific object type
98	591	2	%2d	z^* filter specific object type
99	594	5	%5.2f	u^* filter specific astrometric ra offset (relative to r^*, in arcsec)
100	600	5	%5.2f	g^* filter specific astrometric ra offset (g^* pos - r^*pos, in arcsec)
101	606	5	%5.2f	r^* filter specific astrometric ra offset (relative to r^*, in arcsec)
102	612	5	%5.2f	i^* filter specific astrometric ra offset (relative to r^*, in arcsec)
103	618	5	%5.2f	z^* filter specific astrometric ra offset (relative to r^*, in arcsec)
104	624	5	%5.2f	u^* filter specific astrometric dec offset (u^* pos - r^* pos, in arcsec)
105	630	5	%5.2f	g^* filter specific astrometric dec offset (relative to r^*, in arcsec)
106	636	5	%5.2f	r^* filter specific astrometric dec offset (relative to r^*, in arcsec)
107	642	5	%5.2f	i^* filter specific astrometric dec offset (relative to r^*, in arcsec)
108	648	5	%5.2f	z^* filter specific astrometric dec offset (relative to r^*, in arcsec)
109	654	10	%8x	opdb object status (primary/secondary bit flag)
110	665	4	%4d	parent id (if child; -1 if no parent)



	Bits for 'flags' fields (Object Flags, filter specific object bit flags).

  AR_DFLAG_CANONICAL_CENTER =    0x1, /* used canonical, not local, centre   */
  AR_DFLAG_BRIGHT       =        0x2, /* detected by Bright Objects          */
  AR_DFLAG_EDGE         =        0x4, /* object is too close to edge of frame*/
  AR_DFLAG_BLENDED      =        0x8, /* object is/was blended               */
  AR_DFLAG_CHILD        =       0x10, /* object is a child                   */
  AR_DFLAG_PEAKCENTER   =       0x20, /* given centre position of peak pixel */
  AR_DFLAG_NODEBLEND    =       0x40, /* no deblending attempted             */
  AR_DFLAG_NOPROFILE    =       0x80, /* too small to estimate a profile     */
  AR_DFLAG_NOPETRO      =      0x100, /* no Petrosian radius                 */
  AR_DFLAG_MANYPETRO    =      0x200, /* more than one Petrosian radius      */
  AR_DFLAG_NOPETRO_BIG  =      0x400, /* no Petrosian radius as object is too big */
  AR_DFLAG_DEBLEND_TOO_MANY_PEAKS = 0x800, /* too many peaks to deblend      */
  AR_DFLAG_CR           =     0x1000, /* contains a CR pixel                 */
  AR_DFLAG_MANYR50      =     0x2000, /* more than one 50% radius            */
  AR_DFLAG_MANYR90      =     0x4000, /* more than one 90% radius            */
  AR_DFLAG_BAD_RADIAL   =     0x8000, /* some low S/N radial points          */
  AR_DFLAG_INCOMPLETE_PROFILE = 0x10000, /* r_P includes off-frame pixels    */
  AR_DFLAG_INTERP       =    0x20000, /* object contains interpolated pixels */
  AR_DFLAG_SATUR        =    0x40000, /* object contains saturated pixels    */
  AR_DFLAG_NOTCHECKED   =    0x80000, /* object contains NOTCHECKED pixels   */
  AR_DFLAG_SUBTRACTED   =   0x100000, /* object had wings subtracted         */
  AR_DFLAG_NOSTOKES     =   0x200000, /* object has no measured stokes params*/
  AR_DFLAG_BADSKY       =   0x400000, /* sky level so bad that object is -ve */
  AR_DFLAG_PETROFAINT   =   0x800000, /*  1 == Petrosian radius too faint     */
  AR_DFLAG_TOO_LARGE    =  0x1000000, /* object is too large                 */
  AR_DFLAG_DEBLENDED_AS_PSF = 0x2000000, /* deblender treated obj as PSF     */
  AR_DFLAG_DEBLEND_PRUNED = 0x4000000, /* deblender pruned peak list         */
  AR_DFLAG_ELLIPFAINT   = 0x8000000, /* Centre's fainter than desired elliptical isophote */
  AR_DFLAG_BINNED1      = 0x10000000, /* object was found in 1x1 binned image */
  AR_DFLAG_BINNED2      = 0x20000000, /* object was found in 2x2 binned image */
  AR_DFLAG_BINNED4      = 0x40000000, /* object was found in 4x4 binned image */
  AR_DFLAG_SPARE1       = 0x80000000  /* Spare value; largest flag value */




	Bits for 'status' field (opdb object status).

  AR_OBJECT_STATUS_SET        = 0x1,    /* This object's status has been set */
                                        /* in reference to its own run.      */
  AR_OBJECT_STATUS_GOOD       = 0x2,    /* Good as determined by its         */
                                        /* individual detection flags.       */
                                        /* Absence implies bad.  This flag is*/
                                        /* set by "setObjectStatus".         */
  AR_OBJECT_STATUS_DUPLICATE  = 0x4,    /* Duplicates a detection in an      */
                                        /* adjacent field of the same Frames */
                                        /* Pipeline Run.  Don't use.  This   */
                                        /* is set by "setObjectStatus".      */
  AR_OBJECT_STATUS_OVERLAP    = 0x8,    /* Lies in the overlap region but    */
                                        /* doesn't duplicate a detection in  */
                                        /* an adjacent field of the same     */
                                        /* FramesPipeline Run.  Don't use.   */
                                        /* This is set by "setObjectStatus". */
  AR_OBJECT_STATUS_OK_RUN     = 0x10,   /* Located within the primary range  */
                                        /* of rows for this field, if it is  */
                                        /* also GOOD then this is a usable   */
                                        /* object.  This flag is set by      */
                                        /* "setObjectStatus".                */
  AR_OBJECT_STATUS_RESOLVED   = 0x20,   /* This object has been resolved     */
                                        /* against other runs.               */
  AR_OBJECT_STATUS_BSEGMENT   = 0x40,   /* Belongs to a BAD segment.         */
  AR_OBJECT_STATUS_SSEGMENT   = 0x80,   /* Belongs to a SECONDARY segent.    */
                                        /* This does not imply that this is a*/
                                        /* secondary object.                 */
  AR_OBJECT_STATUS_PSEGMENT   = 0x100,  /* Belongs to a SECONDARY segment.   */
                                        /* This does not imply that this is a*/
                                       /* primary object.                   */
  AR_OBJECT_STATUS_FIRST_FIELD= 0x200,  /* Belongs to the first field in its */
                                        /* segment.  Used to distinguish     */
                                        /* objects in fields shared by two   */
                                        /* segments.                         */
  AR_OBJECT_STATUS_OK_SCANLINE= 0x400,  /* Lies within valid nu range        */
                                        /* for its scanline.                 */
  AR_OBJECT_STATUS_OK_STRIPE  = 0x800,  /* Lies within valid eta range       */
                                        /* for its stripe.                   */
  AR_OBJECT_STATUS_SECONDARY  = 0x1000, /* This is a secondary survey object.*/
  AR_OBJECT_STATUS_PRIMARY    = 0x2000, /* This is a primary survey object.  */
  AR_OBJECT_STATUS_TARGET     = 0x4000  /* This is a spectroscopic target.   */



Defines for objc_type field (Type field):

   Unknown        0
   Cosmic ray     1
   Defect         2
   Galaxy         3
   Ghost          4
   Known object   5
   Star           6
   Star trail     7
   Sky            8

Note on flux-magnitude system

The magnitudes listed in the calibrated files are generated from the instrumental fluxes (counts or DN) via a formula suggested by Robert Lupton, known as 'Inverse hyperbolic sine magnitudes'. These 'magnitudes' have the nice property of not blowing up for an instrumental detection of zero or negative count rates (as one often has for faint, upper limit, sky-subtracted measurements). The standard magnitude and mag error is schematically calculated by a formula such as:

mag = -2.5log10(count_rate) + zeropoint

magErr ~ [2.5/ln(10)]*count_rate_Err/count_rate

Where count_rate is 'counts per second', zeropoint is the mag system zeropoint (color terms, extinction neglected in this example), and count_rate_Err is the statistical or other error in the count rate.

The 'inverse hyperbolic sine magnitudes' are calculated by:

imag = -[2.5/ln(10)]*arcsinh(count_rate/A) + [2.5/ln(10)]*ln(2.0/A) + zeropoint

imagErr = [2.5/ln(10)]*count_rateErr/sqrt(count_rate*count_rate+A*A)

where arcsinh(x) = ln(x+sqrt(1+x*x)).

Here, count_rate, count_rateErr and zeropoint are identical to the standard magnitude quantities. The quantity "A" is a fixed constant which acts to 'soften' the magnitude-count relation for measured count rates <= 0. For the current data, A = 0.001 counts/sec (for all filters). In actual practice A should be chosen (and will be chosen) separately for each filter to a value about 1/2 the rms sky noise per pixel (in counts/sec).

These imagnitudes have the nice property that for large count rates they are indistinguishable from standard magnitudes, while for upper limit detections (<= 0 DN/sec), they continue the magnitude and error system smoothly without infinities or artificial conventions.

As one browses the t_0311.txt and t_0311.fit calibrated object files, one will notice that many magnitudes are listed as extremely faint numbers (i.e. u^* = 31.00 +/- 2.00 magnitudes). These are, of course, really upper limit detections and should be treated carefully.

Note on magnitude system

The SDSS magnitude system has not yet been systematically set up as of this printing. Thus, the absolute calibration of the u^*, g^*, r^*, i^*, and z^* magnitudes presented here are unofficial, and may differ from the final calibrated magnitudes on the u', g', r', i', z' system for these same objects by 0.1 mag or more. The limiting detection magnitudes for the present data are approximately:

u^* < 22.1, g^* < 22.4, r^* < 22.5, i^* < 22.2, z^* < 20.3.