2 Observations and photometry

We have used a number of optical/near-IR (NIR) resources in order to compose a well sampled SED (see Table 1). UBVI observations were carried out with the 3.6-m ESO telescope (3.6ESO) equipped with EFOSC2, covering a field of view (FOV) of $5\farcm5 \times 5\farcm5$. These observations were carried out in $2\times 2$ binning mode, providing a pixel scale of $0\hbox{$.\!\!^{\prime\prime}$ }32$/pix. R-band measurements were obtained with the UT1 of the 8.2-m Very Large Telescope (8.2VLT) equipped with FORS1 and are published in Piro et al. (2002). The Z-band observations were carried out during two consecutive nights with the 1.54-m Danish Telescope (1.54D) equipped with DFOSC, which provides a FOV of $13\hbox{$.\mkern-4mu^\prime$ }7 \times 13\hbox{$.\mkern-4mu^\prime$ }7$ and a pixel scale of $0\hbox{$.\!\!^{\prime\prime}$ }39$/pix.

 

 

Table 2: Magnitudes of the host in the UBVRIZJs HKs bands. Several characteristics of the filters are displayed: filter name (1), effective wavelength (2) and bandpass width (3). The fourth column shows the measured magnitudes (in the Vega system and not corrected from Galactic reddening). To facilitate the calculation of the AB magnitudes, and consequently the flux densities for each band, the AB offsets are provided in the fifth column.

Filter	Effective	Bandpass	Magnitude	ABoff
name	wavelength (Å)	width (Å)
U (ESO#640)	3718.8	172.9	23.54$\pm$0.13	0.73
B (ESO#639)	4372.6	701.4	24.40$\pm$0.13	-0.07
V (ESO#641)	5563.9	856.4	24.22$\pm$0.08	0.04
R (ESO R_BESSEL+36)	6608.5	1300.3	23.46$\pm$0.10$^{\dag }$	0.23
I (ESO#705)	7950.2	844.0	22.49$\pm$0.12	0.45
Z (ESO#462)	9477.4	985.1	22.83$\pm$0.28	0.56
Js (ISAAC)	12498.9	957.8	21.98$\pm$0.10	0.94
H (SOFI)	16519.6	1732.3	21.51$\pm$0.23	1.41
Ks (ISAAC)	21638.0	1637.9	20.94$\pm$0.14	1.87

$\dag$ Published in Piro et al. (2002).

The H-band observations were acquired with the 3.58-m New Technology Telescope (3.58NTT) using SOFI in the large FOV mode, which provides a FOV of $4\hbox{$.\mkern-4mu^\prime$ } 9 \times 4\hbox{$.\mkern-4mu^\prime$ } 9$ and a pixel scale of $0\hbox{$.\!\!^{\prime\prime}$ }292$/pix. The Js and Ks-band observations are based on the UT1 of the 8.2VLT equipped with ISAAC, allowing us to cover a FOV of $2\hbox{$.\mkern-4mu^\prime$ }5 \times 2\hbox{$.\mkern-4mu^\prime$ }5$ with a pixel scale of $0\hbox{$.\!\!^{\prime\prime}$ }148$/pix. In Table 1 we provide the observing log of our optical and NIR observations.

Figure 1: The image shows the co-added V-band image taken at the 3.6ESO telescope at 13.219-13.253/09/01 UT. The objects contained in the circles are the ones with redshifts consistent with 0.746 < z < 0.946. As it can be seen there is no obvious concentration of these galaxies around the host. The circle radius is proportional to 1/|MB|, so the fainter the galaxy the larger the circle. The host galaxy is indicated by the tick marks. The numbers label the secondary NIR standards shown in Table 3. The FOV covered by the image corresponds to $5^{\prime } \times 5^{\prime }$.

Given that every extended source shows a different photodensity profile (or FWHM), an unique fixed Aperture Photometry (or static aperture photometry, AP hereafter) would yield unsatisfactory results. On the other hand, Isophotal Photometry (IP) would also not provide optimum photometry, since performing IP we would not consider the same fraction of each galaxy in the different bands due to colour-dependent morphologies and seeing. To solve this problem the total integrated photometry given by SExtractor was used (Bertin & Arnouts 1996). For each object SExtractor performs two types of total integrated photometry: the Adaptative Aperture Photometry (AAP) and the Corrected Isophotal Photometry (CIP). The AAP and CIP supersede the values given by the AP and IP, respectively, applying to them an aperture correction. For each object SExtractor considers the photometry output given by the AAP, except if a neighbour is found biasing the flux by more than 10%. If this is the case, SExtractor chooses the value given by the CIP (see Bertin & Arnouts 1996 for details). The host galaxy of GRB 000210 is well isolated and hence its photometry is not affected by any neighbours.

The UBVRIZJsHKs-band magnitudes of the host can be seen in Table 2. The UBVRI-band calibration is based on the secondary standards given in Table 2 of Piro et al. (2002). The JHKs-band calibration was performed observing the standard fields sj9105 and sj9172 (Persson et al. 1998) at several airmasses. The derived NIR secondary standards are given in Table 3 and displayed in Fig. 1. The Z-band calibration was carried out observing the spectro-photometric standard stars LTT2415 and LTT1788 (Hamuy et al. 1994) with the 1.54D at an airmass similar to that of the GRB field. The host galaxy BVRI-band magnitudes reported by Piro et al. (2002) are consistent with our magnitudes displayed in Table 2.

 

 

Table 3: NIR secondary standards in the GRB 000210 field.

Name	$\alpha_{2000}$	$\delta_{2000}$	Js	H	Ks
1	1:59:21.51	-40:39:33.4	$17.94 \pm 0.03$	$17.19 \pm 0.03$	$17.00 \pm 0.03$
2	1:59:16.72	-40:40:20.3	$16.77 \pm 0.07$	$16.51 \pm 0.03$	$16.59 \pm 0.04$
3	1:59:16.27	-40:40:27.2	$18.35 \pm 0.08$	$17.69 \pm 0.04$	$17.46 \pm 0.05$

In order to derive the corresponding effective wavelengths and AB offsets we convolved each filter transmission curve with the corresponding CCD efficiency curve (see Table 2). The AB offset is defined as ABoff $= m_{\it AB} - m$, where m is the magnitude in the Vega system and $m_{\it AB}$ is the magnitude in the AB system (given by $m_{\it AB} = -2.5 \times \log f_{\nu} - 48.60$, being $f_{\nu}$ the flux density in erg s^-1 cm^-2 Hz^-1).

The AB offsets of the nine bands have been derived convolving the Vega spectrum taken from the GISSEL98 (Bruzual & Charlot 1993) library ($\alpha$ Lyrae m=0 in all bands by definition) with our UBVRIZJsHKs-band filters and the corresponding CCD efficiency curves. The derived AB offsets (displayed in the last column of Table 2) are similar to the ones reported by Fukugita et al. (1995).

 

 

Table 4: The table displays the parameters of the best host galaxy SED fit when several IMFs, indicated in the first column, are adopted. The rest of the columns display the inferred parameters under the assumed IMF. The second column provides the confidence of the best fit (given by $\chi ^{2}/$dof). The derived photometric redshift is displayed in the third column (and the corresponding 68% and 99% percentile errors). In the fourth and fifth columns the template family of the best fitted SED and the age of the stellar population are given. The sixth column displays the derived value of the host galaxy extinction $A_{\rm V}$. The seventh column displays the derived rest frame absolute B-band magnitude, M_B. The last two columns give the Luminosity of the host in units of $L^{\star }$, when the luminosity functions of Schechter (1976) and Lilly et al. (1995) are used (see Sect. 5.3 for a detailed discussion). The extinction law has been fixed to follow Calzetti et al. (2000) (the effect of the adopted extinction law is discussed in Sect. 5.2). As shown in the first two rows of the table, the resolution of our template grid is not able to make a distinction between most of the properties (Age, $A_{\rm V}$, M_B, $L/L^{\star }$) derived for the Sa55 and MiSc79 IMFs. The photometric redshifts derived for the three IMFs are consistent, within the 99% percentile error range, with the spectroscopic redshift. However, within the 68% precentile ($\sim$$1\sigma$) error range, only the Sa55 and MiSc79 IMFs are consistent, Sc86 is not.

IMF	$\chi ^{2}/$dof	Photometric redshift	Template	Age	$A_{\rm V}$	MB	$L/L^{\star }$	$L/L^{\star }$
		$z^{+ p68\%, p99\%}_{- p68\%, p99\%}$		(Gyr)
Salpeter (1955)	1.096	$\rm0.842^{+0.054, 0.158}_{-0.042, 0.279}$	Stb	0.181	0.00	-20.16	0.67	0.35
Miller & Scalo (1979)	1.046	$\rm0.836^{+0.087, 0.140}_{-0.053, 0.244}$	Stb	0.181	0.00	-20.16	0.67	0.35
Scalo (1986)	0.903	$\rm0.757^{+0.067, 0.219}_{-0.044, 0.132}$	S0	1.015	0.00	-19.90	0.52	0.27