Notes. The content of different columns is: (1) OB association identification number. (2) and (3) Right ascension (RA) and declination (Dec) of the center determined from the average of the positions of the OB members, equinox J2000.0. (4) Number of OB members (N_OB) used in the age and mass determination of the association; this figure includes the blue members listed in Garcia et al. (2009) except for blends found from inspection of images and objects with Q-color bluer than the youngest considered isochrone beyond the errors. (5) Radius estimate, defined as half the maximum distance between two members of the association (non-OB stars are not considered in the calculation). (6) Stellar surface density Σ = N_OB/(πR [pc] ²). (7) Distance of each OB member to its closest neighbor, averaged over the association. (8) log age, determined from the analysis of the association’s Q vs. V_corr diagram. When two values are provided, they represent the age interval enclosing the association. (9) Mass of the most massive star of the association, determined from the position of the star on the Q vs. V_corr diagram and comparison with theoretical isochrones. The provided value is the weighted average of the closest isochrone-point masses to the star. Stars showing blends were not used for M_up determination. First value: initial stellar mass. Second value: current stellar mass. (10) Notes: “?” – dubious association (associations with a small number of members, with a significant fraction under suspicion of being blends or not blue stars); “n” – an individual entry in the table caption; “ ⋄ ” – at least one member was discarded for age determination because of very blue Q (<–1.0); “ ⋆ ” – sequence of objects with Q smaller than the youngest isochrone (in disagreement with the remaining members) but separated from it by a smaller distance than the errors; we checked that these points are neither galaxies nor blends, but were not used for age determination. “†” – the association shows two or more age trends. (11) Average value of extinction towards the bona-fide members of the association, estimated from their colors using Eq. (3) of Paper I; The derived mean value for extinction when averaged over all the OB associations is 0.16. (12) Standard deviation of the extinction towards the members of the association; if only one member is available to calculate the average extinction, this value is set to 99.99. (13) Total mass of the association M_tot  calculated using a regular Salpeter initial mass function (IMF) down to 0.5 M_⊙ (see Sect. 3.4) and maximum mass M_up (1st value of Col. 9). A minimum of two valid members (Col. 4) are required to calculate the association mass, otherwise the value provided here is –1.00E+02. (14) Known spectral types for members, from Bresolin et al. (2007).

Comments on individual associations:

Assoc. #16 may form a larger group with #19, #21 and #22. Their ages are consistent with this hypothesis.

Assocs. #27 and #28: Their brightest members are close to a bright foreground star, which may alter their photometry. The affected members are discarded.

Assoc. #34: The two brightest members (id: 32277, 32501) are blended and therefore discarded for age and mass determination.

Assoc. #48: Visual inspection reveals a blue gaseous filament overlapping with association members. Spitzer observations at 8   μm, which traces PAH and hot dust, found a peak in the area covered by associations #43, #44 and #48.

Assoc. #57’s brightest member may be contaminated by a nearby object.

Assoc. #66: Visual inspection revealed that the brightest member, with very red B−V, is an extended source. This target was discarded.

Assoc. #72’s brightest member may be contaminated by a nearby object. Assocs. #76 and #77 are only 7″ away. Their populations exhibit a similar age distribution.

Assoc. #82: The two brightest members are very close to each other but well resolved in WFPC2 images.

Assoc. #86: Its brightest member shows a lobular shape in WFPC2 images, suggesting that it may be an unresolved triple system.

Assoc. #88: Its B−V vs. V diagram is bimodal, one set of stars following the main sequence and the other having redder B−V colors. The stars in the latter sequence look extended in the INT images, hence were discarded for age and mass determination.

Assoc. #104: Its brightest member (id: 52443) may be contaminated by a nearby object.

Assoc. #107: This association was discarded because it only has two valid members. It is close to #106; the age of the remaining members is in agreement with that of #106.

Assoc. #112: The two brightest members are very close to each other, and might be not well resolved by our photometric reduction.

Assoc. #113: Extra-reddening is seen in the B−V vs. V diagram as an offset.

Assoc. #114: The three brightest blue members are very close to each other, but well resolved in VLT-VIMOS images. After cleaning the Q vs. V_corr diagram from a vertical sequence of stars with redder Q which seem to be blends in the images, there is a very well defined sequence of stars following the 7.1 isochrone.

Assoc. #120: The brightest members are very close to each other.

Assoc. #125: Its brightest member could be contaminated by a nearby red star, although its normal colors suggest otherwise.

Assoc. #134: All members have Q color bluer than the youngest isochrone. The brightest member, however, is close to the 5.9 isochrone within the analysis errors, and was used for age and mass determination.

Assoc. #135: See Sect. 2.3.

Assoc. #151 is the most populated association of our catalog. It includes IC 1613’s supernova remnant (SNR). Our catalog’s entries for the SNR are discarded for age and mass determination.

Assoc. #153’s brightest star was discarded because it is blended with a nearby object.

Assoc. #154 encloses IC 1613’s known oxygen Wolf-Rayet, found by Dodorico & Rosa (1982). Some entries of our OB-star candidate list are knots of the nebula ionized by the WR and discarded for age and mass determination. The points left do not allow us to derive the association age; the value listed in Table 1 is the age of evolutionary points of Z = 0.004 with surface abundances matching those derived for the WO by Kingsburgh & Barlow (1995), and similar T_eff and L_bol. Those points correspond to an initial mass ranging from 60 M_⊙  to 120 M_⊙, having currently  ~10 M_⊙. Since the present analysis does not allow us to refine the result any further, these values were not provided in column M_up.

Assoc. #157: The brightest star is triple in VLT-VIMOS images but unresolved in our catalog.

Assoc. #158 contains 64 029 (or V39), the Luminous Blue Variable candidate (LBVc) we report in Herrero et al. (2010).

Assoc. #160’s brightest star (id: 64338) could be blended to another member (id: 64346).

Assoc. #185: The association displays a very high stellar density. The brightest members might be contaminated by nearby objects.

Assoc. #192: There may be contamination of the brightest star with a red star. The pair is resolved in VLT-VIMOS R-band images. All members have Q color bluer than the youngest isochrone, hence the association is classified “dubious” and we provide N_OB=0 in Table 1. We adopted log age =    5.9.

Assoc. #194: The brightest object of this association is discarded, because it is an edge-on background spiral galaxy.

Assoc. #195: The brightest object of this association is discarded, because it likely is a background galaxy.

Assoc. #197: The brightest member (id: 75661) is discarded for age and mass determination because of its very blue Q color and because it may be contaminated by a nearby object.