2 Millimeter continuum observations

2.1 Source sample and classification

The original goal of our bolometer observations was to make a complete, homogeneous survey for 1.3 mm continuum emission in the embedded YSOs known in the Taurus-Auriga molecular cloud complex (e.g., Myers et al. 1987 - M 87 -; Kenyon et al. 1990 - KHSS90 -; Kenyon & Hartmann 1993; Tamura et al. 1991). Our Taurus subsample thus comprises 26 YSOs which have all been classified as Class I sources, hence candidate protostars (see below), on the basis of their infrared spectral energy distributions (SEDs) (e.g. M 87, KHSS90, and Table 2). It also includes the Class 0 object IRAM 04191+1523 (IRAM 04191 for short) which was discovered in the course of this 1.3 mm continuum survey and is presently undetected shortward of 60 $\mu$m (see André et al. 1999 - hereafter AMB99).

The Taurus cloud has a relatively low spatial density of YSOs and is believed to be representative of the isolated or distributed mode of low-mass star formation (e.g. Gómez et al. 1993). In this case, it has been argued that stars form as a result of the self-initiated collapse of isolated dense cores, possibly driven by ambipolar diffusion (e.g. Myers 1987; Lizano & Shu 1989; Mouschovias 1991; although see Hartmann 2000). Accordingly, Taurus-Auriga may be the nearest ($d =140\$pc) and best example of a major star-forming region where the standard self-similar theory of isolated protostars (see Sect. 1) should apply to a good approximation.

In order to investigate the possible influence of environmental effects on the structure of protostellar envelopes, we then enlarged our initial Taurus sample by including several Bok globules detected by IRAS at d = 160-$460\$pc (e.g. Benson & Myers 1989; Yun & Clemens 1992), as well as embedded YSOs in the Perseus molecular cloud complex at $d \sim 300\$pc (e.g. Bachiller et al. 1991a,b). The Bok globules are small isolated molecular clouds, not clearly associated with any star-forming complex (e.g. Clemens & Barvainis 1988; Lee & Myers 1999), that should also resemble the predictions of the standard protostellar model. By contrast, protostellar evolution in cluster-forming clouds such as Perseus and $\rho$ Ophiuchi is likely to depart significantly from scale-free descriptions (e.g. MAN98; see also Sect. 5 below).

Table 1 lists the most common names of each source in the literature (Col. 1), the abbreviated name adopted in this paper (Col. 2), the source 1950 equatorial coordinates (Cols. 3 and 4, based on the reference listed in Col. 8), along with its adopted distance (Col. 5), bolometric temperature (Col. 6), and bolometric luminosity (Col. 7, based on the reference listed in Col. 9). In total, we took 1.3 mm continuum maps toward 49 embedded YSOs, which are broken down into 4 Class II, 30 Class I, and 15 Class 0 sources.

In this classification, Class 0 sources, distinguished by large submillimeter to bolometric luminosity ratios and self-embedded in massive circumstellar envelopes, are believed to be young protostars at the beginning of the main accretion phase (André et al. 1993, 2000 - hereafter AWB93, AWB2000). Class I sources, characterized by rising SEDs from $\sim$$2~\mu$m to $\sim$ $25{-}100~\mu$m, are interpreted as more evolved protostars which have already accumulated the majority of their final stellar mass but are still accreting matter from a residual envelope plus accretion disk (Lada 1987; M87; André & Montmerle 1994 - hereafter AM94; Chen et al. 1995). Class II and Class III YSOs, with falling infrared SEDs, correspond to pre-main sequence (PMS) stars, e.g., T Tauri stars (see Bertout 1989 for a review), surrounded by a circumstellar disk (optically thick and optically thin, respectively). For the practical purposes of this paper, we have assigned an SED class to each source of Table 2 based on the following limiting ranges of bolometric temperature (cf. Chen et al. 1995, 1997; Gregersen et al. 1997): $\mbox{$T_{\mbox{\tiny bol}}$ }< 70\ \mbox{K}$ for Class 0, $70\ \mbox{K}\le \mbox{$T_{\mbox{\tiny bol}}$ }< 650\ \mbox{K}$ for Class I, and $650\ \mbox{K}\le \mbox{$T_{\mbox{\tiny bol}}$ }< 2\,880\$K for Class II. Note that most of the IRAS Bok globules and Perseus YSOs observed here are confirmed Class 0 protostars (cf. Table 1 of AWB2000).

  

 

Table 1: Sample of observed embedded YSOs

IRAS and other	Adopted	Coordinates		d	$T_{\mbox{\tiny bol}}$	$L_{\mbox{\tiny bol}}$	Coord.	Lum.
source names	name (1)	$\alpha_{\rm 1950}$	$\delta_{\rm 1950}$	(pc)	(K)	($L_\odot$)	ref. (2)	ref. (3)
M04016+2610	L1489	04$^{\rm h}$01$^{\rm m}$40 $\hbox{$.\!\!^{\rm s}$ }$6	26 $\hbox{$^\circ$ }$10 $\hbox{$^\prime$ }$49 $\hbox{$^{\prime\prime}$ }$	140	238	3.7	21	22
M04108+2803A	M04108-A	04$^{\rm h}$10$^{\rm m}$47 $\hbox{$.\!\!^{\rm s}$ }$3	28 $\hbox{$^\circ$ }$03 $\hbox{$^\prime$ }$49 $\hbox{$^{\prime\prime}$ }$	140		0.1	21	17
M04108+2803B	M04108-B	04$^{\rm h}$10$^{\rm m}$49 $\hbox{$.\!\!^{\rm s}$ }$3	28 $\hbox{$^\circ$ }$03 $\hbox{$^\prime$ }$57 $\hbox{$^{\prime\prime}$ }$	140	205	0.6	21	17
K04113+2758	K04113	04$^{\rm h}$11$^{\rm m}$20 $\hbox{$.\!\!^{\rm s}$ }$8	27 $\hbox{$^\circ$ }$58 $\hbox{$^\prime$ }$33 $\hbox{$^{\prime\prime}$ }$	140	606	>1.6	27	17
H04145+2812/V892 Tau	Elias1	04$^{\rm h}$15$^{\rm m}$34 $\hbox{$.\!\!^{\rm s}$ }$5	28 $\hbox{$^\circ$ }$12 $\hbox{$^\prime$ }$02 $\hbox{$^{\prime\prime}$ }$	140	$3\,226$	16	7	7
K04158+2805	K04158	04$^{\rm h}$15$^{\rm m}$52 $\hbox{$.\!\!^{\rm s}$ }$2	28 $\hbox{$^\circ$ }$05 $\hbox{$^\prime$ }$10 $\hbox{$^{\prime\prime}$ }$	140	528	>0.4	15	17
K04166+2706	K04166	04$^{\rm h}$16$^{\rm m}$37 $\hbox{$.\!\!^{\rm s}$ }$8	27 $\hbox{$^\circ$ }$06 $\hbox{$^\prime$ }$29 $\hbox{$^{\prime\prime}$ }$	140	139	0.3	15	17
K04169+2702	K04169	04$^{\rm h}$16$^{\rm m}$53 $\hbox{$.\!\!^{\rm s}$ }$8	27 $\hbox{$^\circ$ }$02 $\hbox{$^\prime$ }$48 $\hbox{$^{\prime\prime}$ }$	140	170	0.8	15	17
K04181+2655	K04181+2655	04$^{\rm h}$18$^{\rm m}$06 $\hbox{$.\!\!^{\rm s}$ }$4	26 $\hbox{$^\circ$ }$55 $\hbox{$^\prime$ }$01 $\hbox{$^{\prime\prime}$ }$	140	278	0.4	15	17
K04181+2654	K04181+2654	04$^{\rm h}$18$^{\rm m}$06 $\hbox{$.\!\!^{\rm s}$ }$9	26 $\hbox{$^\circ$ }$54 $\hbox{$^\prime$ }$04 $\hbox{$^{\prime\prime}$ }$	140	346	0.5	15	17
IRAM04191+1523	IRAM 04191	04$^{\rm h}$19$^{\rm m}$06 $\hbox{$.\!\!^{\rm s}$ }$4	15 $\hbox{$^\circ$ }$22 $\hbox{$^\prime$ }$46 $\hbox{$^{\prime\prime}$ }$	140	18	0.15	1	1
T04191+1523	T04191	04$^{\rm h}$19$^{\rm m}$09 $\hbox{$.\!\!^{\rm s}$ }$6	15 $\hbox{$^\circ$ }$23 $\hbox{$^\prime$ }$20 $\hbox{$^{\prime\prime}$ }$	140	210	0.5	27	22
M04239+2436	M04239	04$^{\rm h}$23$^{\rm m}$54 $\hbox{$.\!\!^{\rm s}$ }$5	24 $\hbox{$^\circ$ }$36 $\hbox{$^\prime$ }$54 $\hbox{$^{\prime\prime}$ }$	140	236	1.3	21	17
M04248+2612/HH31IRS2	M04248	04$^{\rm h}$24$^{\rm m}$52 $\hbox{$.\!\!^{\rm s}$ }$7	26 $\hbox{$^\circ$ }$12 $\hbox{$^\prime$ }$42 $\hbox{$^{\prime\prime}$ }$	140	334	0.4	21	17
Z04260+2642	Z04260	04$^{\rm h}$26$^{\rm m}$00 $\hbox{$.\!\!^{\rm s}$ }$0	26 $\hbox{$^\circ$ }$42 $\hbox{$^\prime$ }$32 $\hbox{$^{\prime\prime}$ }$	140		0.1	9	17
04263+2426/GVTauB	Haro6-10	04$^{\rm h}$26$^{\rm m}$22 $\hbox{$.\!\!^{\rm s}$ }$0	24 $\hbox{$^\circ$ }$26 $\hbox{$^\prime$ }$30 $\hbox{$^{\prime\prime}$ }$	140	253	7.0	21	17
K04264+2433	Elias6	04$^{\rm h}$26$^{\rm m}$28 $\hbox{$.\!\!^{\rm s}$ }$1	24 $\hbox{$^\circ$ }$33 $\hbox{$^\prime$ }$24 $\hbox{$^{\prime\prime}$ }$	140	252	0.5	15	9
F04287+1801	L1551-IRS5	04$^{\rm h}$28$^{\rm m}$40 $\hbox{$.\!\!^{\rm s}$ }$2	18 $\hbox{$^\circ$ }$01 $\hbox{$^\prime$ }$42 $\hbox{$^{\prime\prime}$ }$	140	97	28	14	10
04287+1806	HH30-IRS	04$^{\rm h}$28$^{\rm m}$43 $\hbox{$.\!\!^{\rm s}$ }$3	18 $\hbox{$^\circ$ }$06 $\hbox{$^\prime$ }$02 $\hbox{$^{\prime\prime}$ }$	140		> 0.1	20	24
04287+1807/Haro6-14	HLTau	04$^{\rm h}$28$^{\rm m}$44 $\hbox{$.\!\!^{\rm s}$ }$4	18 $\hbox{$^\circ$ }$07 $\hbox{$^\prime$ }$36 $\hbox{$^{\prime\prime}$ }$	140	576	7.1	7	24
04288+1802	L1551-NE	04$^{\rm h}$28$^{\rm m}$50 $\hbox{$.\!\!^{\rm s}$ }$4	18 $\hbox{$^\circ$ }$02 $\hbox{$^\prime$ }$10 $\hbox{$^{\prime\prime}$ }$	140	75	6	21	5
M04295+2251/L1536-IRS	M04295	04$^{\rm h}$29$^{\rm m}$32 $\hbox{$.\!\!^{\rm s}$ }$2	22 $\hbox{$^\circ$ }$51 $\hbox{$^\prime$ }$11 $\hbox{$^{\prime\prime}$ }$	140	447	0.6	21	21
04296+1725	GGTau	04$^{\rm h}$29$^{\rm m}$37 $\hbox{$.\!\!^{\rm s}$ }$2	17 $\hbox{$^\circ$ }$25 $\hbox{$^\prime$ }$22 $\hbox{$^{\prime\prime}$ }$	140	$2\,621$	2.0	7	17
K04302+2247	K04302	04$^{\rm h}$30$^{\rm m}$16 $\hbox{$.\!\!^{\rm s}$ }$8	22 $\hbox{$^\circ$ }$47 $\hbox{$^\prime$ }$04 $\hbox{$^{\prime\prime}$ }$	140	202	0.3	16	17
T04325+2402/L1535-IRS	T04325	04$^{\rm h}$32$^{\rm m}$33 $\hbox{$.\!\!^{\rm s}$ }$5	24 $\hbox{$^\circ$ }$02 $\hbox{$^\prime$ }$15 $\hbox{$^{\prime\prime}$ }$	140	157	0.9	27	22
K04361+2547	TMR1	04$^{\rm h}$36$^{\rm m}$09 $\hbox{$.\!\!^{\rm s}$ }$8	25 $\hbox{$^\circ$ }$47 $\hbox{$^\prime$ }$28 $\hbox{$^{\prime\prime}$ }$	140	144	3.7	16	22
M04365+2535/L1534	TMC1A	04$^{\rm h}$36$^{\rm m}$31 $\hbox{$.\!\!^{\rm s}$ }$2	25 $\hbox{$^\circ$ }$35 $\hbox{$^\prime$ }$56 $\hbox{$^{\prime\prime}$ }$	140	172	2.4	21	21
K04368+2557	L1527	04$^{\rm h}$36$^{\rm m}$49 $\hbox{$.\!\!^{\rm s}$ }$5	25 $\hbox{$^\circ$ }$57 $\hbox{$^\prime$ }$16 $\hbox{$^{\prime\prime}$ }$	140	59	1.6	18	15
M04381+2540/TMC1	M04381	04$^{\rm h}$38$^{\rm m}$08 $\hbox{$.\!\!^{\rm s}$ }$5	25 $\hbox{$^\circ$ }$40 $\hbox{$^\prime$ }$53 $\hbox{$^{\prime\prime}$ }$	140	139	0.7	21	21
M04385+2550/Haro6-33	TMC1C	04$^{\rm h}$38$^{\rm m}$34 $\hbox{$.\!\!^{\rm s}$ }$6	25 $\hbox{$^\circ$ }$50 $\hbox{$^\prime$ }$44 $\hbox{$^{\prime\prime}$ }$	140	636	>0.4	21	17
M04489+3042	M04489	04$^{\rm h}$48$^{\rm m}$55 $\hbox{$.\!\!^{\rm s}$ }$2	30 $\hbox{$^\circ$ }$42 $\hbox{$^\prime$ }$18 $\hbox{$^{\prime\prime}$ }$	140	399	0.3	21	21
05417+0907	B35	05$^{\rm h}$41$^{\rm m}$44 $\hbox{$.\!\!^{\rm s}$ }$8	09 $\hbox{$^\circ$ }$07 $\hbox{$^\prime$ }$38 $\hbox{$^{\prime\prime}$ }$	460		15	28	8
16442-0930	L260	16$^{\rm h}$44$^{\rm m}$13 $\hbox{$.\!\!^{\rm s}$ }$9	$-09\hbox{$^\circ$ }$29 $\hbox{$^\prime$ }$59 $\hbox{$^{\prime\prime}$ }$	160		1.0	21	21
18148-0440	L483-MM	18$^{\rm h}$14$^{\rm m}$50 $\hbox{$.\!\!^{\rm s}$ }$6	$-04\hbox{$^\circ$ }$40 $\hbox{$^\prime$ }$49 $\hbox{$^{\prime\prime}$ }$	200	48	14	23	18
18331-0035	L588	18$^{\rm h}$33$^{\rm m}$07 $\hbox{$.\!\!^{\rm s}$ }$6	$-00\hbox{$^\circ$ }$35 $\hbox{$^\prime$ }$48 $\hbox{$^{\prime\prime}$ }$	200		?	23
19156+1906	L723-MM	19$^{\rm h}$15$^{\rm m}$42 $\hbox{$.\!\!^{\rm s}$ }$0	19 $\hbox{$^\circ$ }$06 $\hbox{$^\prime$ }$55 $\hbox{$^{\prime\prime}$ }$	300	39	3	2	12
19345+0727	B335	19$^{\rm h}$34$^{\rm m}$35 $\hbox{$.\!\!^{\rm s}$ }$1	07 $\hbox{$^\circ$ }$27 $\hbox{$^\prime$ }$24 $\hbox{$^{\prime\prime}$ }$	250	29	3	3	12
20386+6751	L1157-MM	20$^{\rm h}$38$^{\rm m}$39 $\hbox{$.\!\!^{\rm s}$ }$6	67 $\hbox{$^\circ$ }$51 $\hbox{$^\prime$ }$33 $\hbox{$^{\prime\prime}$ }$	440	42	11	30	30
21106+4712	B361	21$^{\rm h}$10$^{\rm m}$40 $\hbox{$.\!\!^{\rm s}$ }$9	47 $\hbox{$^\circ$ }$12 $\hbox{$^\prime$ }$01 $\hbox{$^{\prime\prime}$ }$	350		4.7	8	8
23238+7401	L1262	23$^{\rm h}$23$^{\rm m}$48 $\hbox{$.\!\!^{\rm s}$ }$7	74 $\hbox{$^\circ$ }$01 $\hbox{$^\prime$ }$08 $\hbox{$^{\prime\prime}$ }$	200		2.3	8	29
	L1448-NW	03$^{\rm h}$22$^{\rm m}$31 $\hbox{$.\!\!^{\rm s}$ }$1	30 $\hbox{$^\circ$ }$35 $\hbox{$^\prime$ }$04 $\hbox{$^{\prime\prime}$ }$	300	24	2.7	6	6
03225+3034/L1448-IRS3	L1448-N	03$^{\rm h}$22$^{\rm m}$31 $\hbox{$.\!\!^{\rm s}$ }$8	30 $\hbox{$^\circ$ }$34 $\hbox{$^\prime$ }$45 $\hbox{$^{\prime\prime}$ }$	300	55	11	11	6
L1448-MM	L1448-C	03$^{\rm h}$22$^{\rm m}$34 $\hbox{$.\!\!^{\rm s}$ }$3	30 $\hbox{$^\circ$ }$33 $\hbox{$^\prime$ }$35 $\hbox{$^{\prime\prime}$ }$	300	55	8	11	6
03258+3104/SVS19	NGC 1333-IRAS 2	03$^{\rm h}$25$^{\rm m}$49 $\hbox{$.\!\!^{\rm s}$ }$9	31 $\hbox{$^\circ$ }$04 $\hbox{$^\prime$ }$16 $\hbox{$^{\prime\prime}$ }$	350	41	40	26	13
	NGC 1333-IRAS 4A	03$^{\rm h}$26$^{\rm m}$04 $\hbox{$.\!\!^{\rm s}$ }$8	31 $\hbox{$^\circ$ }$03 $\hbox{$^\prime$ }$14 $\hbox{$^{\prime\prime}$ }$	350	34	14	25	25
	NGC 1333-IRAS 4B	03$^{\rm h}$26$^{\rm m}$06 $\hbox{$.\!\!^{\rm s}$ }$5	31 $\hbox{$^\circ$ }$02 $\hbox{$^\prime$ }$51 $\hbox{$^{\prime\prime}$ }$	350	36	14	25	25
03282+3035	IRAS 03282	03$^{\rm h}$28$^{\rm m}$15 $\hbox{$.\!\!^{\rm s}$ }$8	30 $\hbox{$^\circ$ }$35 $\hbox{$^\prime$ }$20 $\hbox{$^{\prime\prime}$ }$	300	23	1.5	4	6
	HH211-MM	03$^{\rm h}$40$^{\rm m}$48 $\hbox{$.\!\!^{\rm s}$ }$7	31 $\hbox{$^\circ$ }$51 $\hbox{$^\prime$ }$24 $\hbox{$^{\prime\prime}$ }$	300		<10?	19
M03445+3242/B5-B	B5-IRS1	03$^{\rm h}$44$^{\rm m}$31 $\hbox{$.\!\!^{\rm s}$ }$8	32 $\hbox{$^\circ$ }$42 $\hbox{$^\prime$ }$34 $\hbox{$^{\prime\prime}$ }$	300		9.4	21	21

Notes: ⁽¹⁾ The first letter of the adopted name generally refers to source samples. Thus, "L'' corresponds to the Lynds catalogue (1962); "M'' and "K'' recall IRAS sources selected by M 87 and Kenyon et al. (1990, 1993a, 1993); "H'' and "T'' indicate sources studied by Heyer et al. (1987) and Tamura et al. (1991); "Z'' and "F'' refer to Beichman et al. (1986). ⁽²⁾ and ⁽³⁾ References: (1) AMB99; (2) and (3) Anglada et al. (1991, 1992); (4) Bachiller et al. (1994); (5) and (6) Barsony et al. (1993, 1998); (7) Beckwith et al. (1990); (8) and (9) Beichman et al. (1986, 1992); (10) Butner et al. (1991); (11) Curiel et al. (1990); (12) Davidson (1987); (13) Jennings et al. (1987); (14) Keene & Masson (1990); (15) KHSS90; (16) KCH93; (17) Kenyon & Hartmann (1993); (18) Ladd et al. (1991); (19) McCaughrean et al. (1994); (20) Mundt et al. (1987); (21) M 87; (22) Ohashi et al. (1996); (23) Parker (1988); (24) Reipurth et al. (1993); (25) and (26) Sandell et al. (1991, 1994); (27) Tamura et al. (1991); (28) and (29) Terebey et al. (1992, 1993); (30) Umemoto et al. (1992).

2.2 Bolometer mapping

We carried out our 1.3 mm mapping survey during five observing sessions from 1993 to 1999. All the runs were performed using the IRAM 30 m telescope on Pico Veleta (Spain) and the MPIfR bolometer arrays (now called MAMBO, e.g. Kreysa et al. 1998) with 7 channels (in 1993 and 1994), 19 channels (in 1995 and 1996), and 37 channels (in 1999). The passband of these bolometers has an equivalent width $\approx$70 GHz and is centered at $\nu_{\rm eff} \approx 240$ GHz (e.g. Kreysa et al. 1998).

Each YSO of Table 1 was first observed at its nominal infrared position in the "on-off'' observing mode, and then mapped in the "multi-point'' or "on-the-fly'' mode.

The multi-point mapping mode was mainly used in 1993, for sources which were too weak to be observed in the on-the-fly mapping mode with the 7-channel bolometer. Each multi-point map consists of several (>5) on-off integrations giving fluxes at a few ( $> 5 \times 7 = 35$) offsets around the nominal source position.

In the dual-beam on-the-fly mapping mode, the telescope is scanned continuously in azimuth along each row while wobbling. For each channel, the raw data corresponding to a single on-the-fly coverage consist of several rows taken at a series of elevations. We used a scanning velocity of 4 $\hbox{$^{\prime\prime}$ }$/s or 8 $\hbox{$^{\prime\prime}$ }$/s, and a sampling of 2 $\hbox{$^{\prime\prime}$ }$ (resp. 4 $\hbox{$^{\prime\prime}$ }$) in azimuth and 4 $\hbox{$^{\prime\prime}$ }$ in elevation. The wobbler frequency was set to 2 Hz and the wobbler throw (in azimuth) was typically 32 $\hbox{$^{\prime\prime}$ }$. The typical size of the maps depends on the bolometer array used: $\sim$ $1\hbox{$^\prime$ }\times 1\hbox{$^\prime$ }$, $\sim$ $3\hbox{$^\prime$ }\times 2\hbox{$^\prime$ }$, and $\sim$ $4\hbox{$^\prime$ }\times 3\hbox{$^\prime$ }$for the 7-channel, 19-channel, and 37-channel arrays, respectively.

The dual-beam maps were reduced with the IRAM software for bolometer-array data ("NIC''; cf. Broguière et al. 1995) which uses the EKH restoration algorithm (Emerson et al. 1979).

The FWHM size of the main beam was measured to be $HPBW \sim 11\hbox{$^{\prime\prime}$ }-12\hbox{$^{\prime\prime}$ }$ using Uranus, Mars, and other strong point-like sources such as quasars. The absolute pointing of the telescope was checked every $\sim$1 hr and found to be accurate to better than $\sim$ $3\hbox{$^{\prime\prime}$ }$- $5\hbox{$^{\prime\prime}$ }$(maximum deviation in both coordinates).

Most of the data benefited from good weather conditions. The zenith atmospheric optical depth, monitored by "skydips'' every 1-2 hr, was between $\sim$0.1 and $\sim$0.4. Calibration was achieved through on-the-fly mapping and on-off observations of the primary calibrators Uranus and Mars (e.g. Griffin & Orton 1993 and references therein). In addition, L1551-IRS5 and L1448-N were used as secondary calibrators in Taurus and Perseus, respectively. The 1.3 mm flux densities adopted for L1551-IRS5 are $\sim$1.5 Jy in an $11\hbox{$^{\prime\prime}$ }$ beam and $\sim$3.4 Jy integrated over a $60\hbox{$^{\prime\prime}$ }$ diameter aperture. L1551-IRS5 was mapped once a day and observed in the on-off mode before and after each YSO map in Taurus. Likewise, L1448-N whose adopted 1.3 mm peak flux is $\sim$4.1 Jy/beam was observed before and after each map in Perseus. The relative calibration accuracy was found to be better than $\sim$10% in Taurus by comparing independent observations of sources mapped several times. Within the subsample of isolated IRAS globules and Perseus protostars, the relative calibration accuracy is slightly worse, i.e., $\sim$20%. The overall, absolute calibration uncertainty is estimated to be $\sim$20%.