5 Comments on individual sources

 

In the following, we present a brief description of the basic stellar data for each Herbig AeBe star and of the associated stellar field. Where available, we also give some information about the amount of gas and dust associated with the stars, since this information will prove useful for the discussion of the clustering properties of the Herbig AeBe stars (see Testi et al. 1998). We have recomputed the mass of circumstellar dust and gas (in units of $M_\odot$) from the 1.3 mm flux as $1.28\ 10^{-4}\ (D/140$ pc)$^2\,F_{\rm 1.3~mm}$(mJy) (Natta et al. 1997). Often there are large discrepancies between the circumstellar masses inferred from millimetric continuum observations and those derived from molecular data. Whenever possible, we give both of them. As in Table 2, the sources are ordered by decreasing spectral type.

For each Herbig AeBe system observed at TIRGO, we show the J- and K-band images, the (J-H, H-K) colour-colour diagram, and the stellar surface density profile at K-band. We determine ${\cal N}_{K}$ and $I_{\rm C}$ and provide an estimate of the radius of the stellar cluster, when a stellar density enhancement is present above the background. We have included the TIRGO observations of the 19 fields analysed in Paper I since only few fields were shown there. The 1996 NOT observations are limited to the K-band and therefore we show the K-band image and the corresponding surface density profile only. White pixels on top of the brighter stars indicate that these sources are saturated (or fall in the nonlinear regime of the detector).

For most of the sources observed in the earliest runs at the TIRGO, the scatter of the points in the colour-colour diagram is due either to the systematic uncertainties described in Paper I and in Hunt et al. (1996) or to the unstable atmospheric conditions which appear to plague more heavily the H-band data. In a few cases (HK Ori, HD 259431, LkH$\alpha$ 218, HD 245185, and Z CMa) a systematic offset in the H-band of $\sim0.2$ - 0.3 magnitudes is evident.

5.1 V 645 Cyg (AFGL 2798)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (6 kpc) and the spectral type are from Cohen (1977). There is some controversy on the actual values of the parameters for this star, which some authors (Goodrich 1986; Hamann & Persson 1992; Corcoran & Ray 1998) classify as A0 at distance 3500 pc.

Far-infared studies of this region (Natta et al. 1993) reveal extended emission at 50 and 100 $\mu$m, typical of an extended envelope surrounding the star. The estimated total mass of the envelope (within 0.5 pc from the star) is 78 $M_\odot$.Di Francesco et al. (1997) refer of a possible detection at 2.7 mm with the Plateau de Bure interferometer. In the radio continuum (3.6 cm; Skinner et al. 1993) the emission is extended, with an intensity consistent with the O7 classification of Cohen (1977).

V 645 Cyg is located in a region of extended CO and NH₃ emission (Torrelles et al. 1983, 1989). Torrelles et al. (1987) and Verdes-Montenegro et al. (1991) detected a massive CO outflow associated with the star.

(Fig. 4). The star is embedded in a bright diffuse nebula (see also Goodrich 1986). We detect a group of stars with a projected radius of $\sim0.6$ pc.

 

Figure 4:   V 645 Cyg. Left: K-band image; right: K-band source surface density profile

5.2 MWC 297  (SS73 164)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (450 pc) and the spectral type (O9) from Hillenbrand et al. (1992).

Hillenbrand et al. (1992) measured a 1.3 mm flux of 110 mJy in a region of 0.06 pc size, which roughly corresponds to a circumstellar mass of 0.15 $M_\odot$.Mannings (1994) detected the star at all submm wavelengths; the SED is consistent with simple disc emission. However, Di Francesco et al. (1994) spatially resolve the source, implying contribution from an extended envelope. The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 1500 $M_\odot$ in a region of $\sim$1 pc in size.

(Fig. 5). Very bright star surrounded by a diffuse nebula. A stellar group is detected with a radius $r\sim 0.05$ pc.

 

Figure 5:   MWC 297. Left: K-band image; right: K-band source surface density profile

5.3 MWC 137  (PK 195-00.1; PN VV 42)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (1300 pc) and spectral type (B0) are from Hillenbrand et al. (1992). There is a big discrepancy with Berrilli et al. (1992) parameters, but the latter seem rather uncertain.

The star was once believed to be a planetary nebula (Perek & Kohoutek 1967; Acker et al. 1987; Acker & Stenholm 1990) and its true nature is still disputed. However, Zijlstra et al. (1990) put it in the list of misclassified planetary nebulae from VLA data: it is shown to be a compact HII region based on radio morphology, stronger emission than most Planetary Nebulae and from its location in the IRAS colour-colour diagram.

The far-infrared (FIR) and (sub)mm environment of this star has been studied extensively in recent years. Di Francesco et al. (1994) found that the emission at 50 and 100 $\mu$m peaks on the star but is quite extended. Standard accretion disks cannot be the sole source of FIR emission and most of the emission comes from an extended circumstellar envelope. The same conclusion is reached through submm observations by Mannings (1994), who found the emission at 350 and 450 $\mu$m to be well in excess of that expected from an optically thick disk. The star has a 1.3 mm flux of 190 mJy (Hillenbrand et al. 1992), which corresponds to a mass of circumstellar material of about 2 $M_\odot$ in a region of 0.18 pc size. Di Francesco et al. (1997) possibly detect the source at 2.7 mm with the PdB interferometer giving further support to the hypothesys of the young nature of the object.

The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 83 $M_\odot$ in a region of <0.8 pc size. Higher resolution observations by Fuente et al. (1998) show that on a scale of 0.08 pc the amount of gas and dust is reduced to $\sim$2 $M_\odot$.

(Fig. 6). The Herbig AeBe star is surrounded by a double shell like reflection nebulosity. Within the nebula many faint stars are detected. The source surface density profile clearly shows a peak around MWC 137 with radius $r\sim0.4$ pc.

 

Figure 6:   MWC 137. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.4 R Mon  (BD+08$^\circ$1427; MWC 151)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). These estimates may be affected by the bright nebulosity associated to the star. The distance (800 pc) is from Finkenzeller & Mundt (1984) and the spectral type (B0) from Cohen & Kuhi (1979).

Near infrared adaptive optics and visible HST imaging (Close et al. 1997) reveal a faint companion and resolve the double helix structure of the diffuse nebulosity. No other object is found close to the Herbig Be star.

Natta et al. (1993) resolve the 100 $\mu$m emission associated to the star and determine an envelope mass >36 $M_\odot$ (within a radius of 0.5 pc). The 1.3 mm flux (Hillenbrand et al. 1992) yields a value of the circumstellar mass in a region of 0.1 pc size of about 0.4 $M_\odot$.

(Fig. 7). The Herbig AeBe star is at the apex of an extended bright nebulosity. The source density profile shows a dip around the star position suggesting that background stars and possibly faint young companions might be hidden either by the bright nebula or a molecular clump.

 

Figure 7:  R Mon. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.5 BHJ 71 (V374 Cep, AS 505)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (730 pc) is from Berrilli et al. (1992) and the spectral type (B0) from Finkenzeller & Mundt (1984).

Both the distance and the spectral classification are very uncertain. The distance quoted by Berrilli et al. (1992) is derived assuming that it is a member of the Cepheus OB3 association.

(Fig. 8). The field is very crowded, a moderate density enhancement with $r\sim 0.15$ pc is marginally detected.

 

Figure 8:  BHJ 71. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.6 MWC 1080

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (2500 pc) is from Cantó et al. (1984) and the spectral type (B0) from Cohen & Kuhi (1979).

The uncertainty on the stellar parameters is not large in this case. Agreement exists in the literature about the fact that the star is indeed young and a bona fide Herbig AeBe star. This is supported, among other things by the detection of a molecular outflow (Levreault 1988) and high velocity CO line emission (Koo 1989; Wu et al. 1996). Zinnecker & Preibisch (1994) have detected strong X-ray emission from the object. Leinert et al. (1997) classify the star as an eclipsing binary and detect an infrared companion at 0.75$^{\prime\prime}$. The companion appears to have a high luminosity and could possibly be a second Herbig AeBe star in the region. This result is confirmed by Pirzkal et al. (1997). These findings support the colliding winds hypothesis for the X-ray emission.

The star is detected at 100 $\mu$m by di Francesco et al. (1994), who derive an apparent size of $\sim29^{\prime\prime}$ (corresponding to $\sim3\ 10^4$ AU). The presence of an extended component is also inferred from the submm observations of Mannings (1994), who measures 350 and 450 $\mu$m flux densities in excess to the prediction of a simple optically thick accretion disk model. The source is extended also at 1.3 mm. The flux in a 28$\hbox{$^{\prime\prime}$}$ beam is 540 mJy (Hillenbrand et al. 1992), which corresponds to about 22 $M_\odot$ in a region of about 0.34 pc size. No compact 2.7 mm emission is detected by di Francesco et al. (1997).

The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$1400 $M_\odot$ in a region of $\sim$1.1 pc size. Fuente et al. (1998) have observed the star at the IRAM-30 m telescope and detected emission both in the line and continuum, obtaining $M=11\ M_\odot$ within 0.08 pc. On the other hand, Molinari et al. (1996) report no detection of NH₃(1,1) and (2,2) line emission and of H₂O maser emission.

(Fig. 9). In our NIR images, a conspicuous group of stars is detected close to the Herbig Be star and embedded in a diffuse nebulosity. The radius of the group is $r\sim 0.7$ pc.

 

Figure 9:  MWC 1080. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.7 AS 310  (PK 026+01.1; PN VV 425)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (2500 pc) and the spectral type (B0) are from Henning et al. (1994).

The star is associated with the HII region S61 (Georgelin & Georgelin 1970). Henning et al. (1994) observed the source at 1.3 mm and derived a gas mass of $30~M_\odot$.It is known to be a binary system (Bastian & Mundt 1979) with separation 4.4 arcsec. Ageorges et al. (1997) high angular resolution NIR observations have revealed 4 more sources located close to the binary (all within 5$^{\prime\prime}$) and conclude that there is a small cluster around the Herbig AeBe star.

AS 310 has a 1.3 mm flux of 190 mJy (Henning et al. 1994), from which we infer a mass of 8 $M_\odot$ in a region of 0.28 pc size.

(Fig. 10). In our NIR image the field is extremely crowded, however a clear peak in the source surface density profile is seen with a radius of $\sim0.4$ pc. This finding suggests that Ageorges et al. (1997) are in fact detecting the brightest (and closer to the Herbig AeBe star) members of a conspicuous cluster.

 

Figure 10:  AS 310. Left: K-band image; right: K-band source surface density profile

5.8 RNO 6 (HBC 334; IRAS 02130+5509)

The star is from the Red and Nebulous Objects catalogue of Cohen (1980), who give the spectral type that we are using (B1). The distance (1600 pc) is from Scarrot et al. (1986). V and (B-V) from Herbig & Bell (1988) catalogue. It is not included in the list of Finkenzeller & Mundt (1984).

(Fig. 11). An arc-shaped nebula is detected at all NIR wavelegths. The source surface density profile shows a clear enhancement toward the central position. The radius of the density peak is $r\sim0.3$ pc.

 

Figure 11:  RNO 6. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.9 HD 52721  (BD-11$^\circ$1747; MWC 164; IRAS 06594-1113; GU CMa; VDB 88)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (1150 pc) is from Finkenzeller & Mundt (1984) and the spectral type (B2) from Hillenbrand et al. (1992).

New spectroscopic results (van den Ancker et al. 1997) confirm that the spectral type is B2Ve. Evidence from rotational velocity and the small IR excess supports the interpretation that it could be a classical Be star rather than a Herbig Be star. However, we detect a measurable excess of stars around it (Paper I) supporting the hypothesis that it is indeed a young star surrounded by a group of lower luminosity objects. The estimate of the distance (1150 pc) comes from Herbst (1982) who assumed that the star is at the same distance of the nebulosity of CMa R1.

Fuente et al. (1998) have observed this object at mm wavelengths; they find that the star sits in a large cavity devoid of molecular gas.

(Fig. 12). Very crowded field with a marginally detected source enhancement with radius $r\sim 0.6$ pc.

 

Figure 12:  HD 52721. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.10 BD +65$^\circ$1637  (NGC 7129; V361 Cep; HBC 730; AS 475)

The V-magnitude, (B-V) colour and spectral type (B2) are from Shevchenko et al. (1993). The distance (1 kpc) is from Finkenzeller & Mundt (1984).

This star is in the same molecular complex that harbors LkH$\alpha$ 234. Large scale observations of the molecular emission have shown that BD +65$^\circ$1637 (and most of the cluster, see below) are at the center of a region evacuated from the molecular material, while LkH$\alpha$ 234 is at the edge of a molecular ridge (Fuente et al. 1998). From line and continuum measurements the mass of gas and dust associated with the star is very modest ($M_{^{13}\rm CO}=0.4\,\, M_\odot$,$M_{\rm CS}=1.0\,\, M_\odot$, $M_{\rm dust}=0.6\,\, M_\odot$).

(Fig. 13). A clear enhancement of stars is detected between the two Herbig AeBe stars BD +65$^\circ$1637 (the more massive visible star in the region) and LkH$\alpha$ 234, the brightest source in the field at K-band, located toward the north east with respect to the center. The peak of the stellar surface density profile centered on the B2 star has a radius of $\sim0.4$ pc. Diffuse emission is clearly detected around LkH$\alpha$ 234 and in a $\sim2$ arcminute long filament, which is probably marking the interaction between the radiation field of BD +65$^\circ$1637 and the surface of the molecular cloud that sorrounds the stellar group toward the south east. The large scale molecular observations of Fuente et al. (1998) confirmed that this structure is indeed tracing the edge of the molecular cloud.

 

Figure 13:  BD +65$^\circ$1637. Left: K-band image; right: K-band source surface density profile

5.11 HD 216629 (BD+61$^\circ$2361; MWC 1075; IL Cep)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (725 pc) is from Garmany (1973) and the spectral type that we assume (B2) is from Finkenzeller & Mundt (1984).

The NIR images of Pirzkal et al. (1997) reveal a companion at 6.96'' with no difference at K between the primary and the companion star.

(Fig. 14). Very crowded field with a moderate source surface density enhancement with $r\sim 0.1$ pc detected. The bright companion detected by Pirzkal et al. (1997) is clearly revealed.

 

Figure 14:  HD 216629. Left: K-band image; right: K-band source surface density profile

5.12 BD+40$^\circ$4124  (MWC 340; V 1685 Cyg; He 3-1882)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (1000 pc) and spectral type (B2) from Finkenzeller & Mundt (1984).

The object is detected at 1.3 mm (Hillenbrand et al. 1992); the corresponding circumstellar mass is about 1.5 $M_\odot$ in a region of 0.14 pc size. In the 2.7 mm observations of di Francesco et al. (1997) the star itself is not detected. However, they detect a strong, unresolved source 0.9'' north of V1318 Cyg S. This source is also closest to the emission peak at 800 $\mu$m (Aspin et al. 1994), and the center of the outflow and H₂O maser emission (Palla et al. 1995), and it is believed to be one of the youngest sources in the region.

The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 862 $M_\odot$ in a region of =0.7 pc size.

(Fig. 15). An embedded rich group is detected within $r\sim 0.2$ pc from the Herbig Be star, embedded in a diffuse nebulosity. There are at least three bright members in the group at K-band. This region has been studied in detail by Aspin et al. (1994), Hillenbrand et al. (1995) and Palla et al. (1995). The group is embedded in a compact molecular clump which prevents the detection of at least 70% of the sources at optical (R) wavelengths.

 

Figure 15:  BD+40$^\circ$4124. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.13 HD 37490 ($\omega$ Ori; MWC 117; BD+04$^\circ$1002; HR 1934; IRAS 05365+0405; SAO 113001; HIP 26594)

The V-magnitude and (B-V) colour are from Berrilli et al. (1992), the distance (360 pc) from Racine (1968), spectral type (B3) from Finkenzeller & Mundt (1984).

Hillenbrand et al. (1992) give a distance of 360 pc and a spectral type B2; from the shape of the SED they classify it as a Group III Herbig AeBe star. Hipparcos measurements (van den Anker et al. 1998) give a parallax of 2 $\pm$ 0.9 mas and a distance > 210 pc.

(Fig. 16). The bright Herbig AeBe star is surrounded by a faint nebulosity. A stellar density enhancement with radius $r\sim 0.14$ pc is detected.

 

Figure 16:  HD 37490. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.14 HD 200775  (BD+67$^\circ$1283; MWC 361; HBC 726)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (600 pc) and the spectral type (B3) are from Finkenzeller & Mundt (1984).

The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 720 $M_\odot$ in a region of $\sim$0.8 pc size. High resolution observations by Fuente et al. (1998) show that on a scale of 0.08 pc the amount of gas and dust is reduced to $\sim$1.5 $M_\odot$.

(Fig. 17). The star is surrounded by a bright nebulosity, which is probably marking the region where the stellar radiation field interacts with the surrounding molecular material. No source surface density enhancement is detected.

 

Figure 17:  HD 200775. Left: K-band image; right: K-band source surface density profile

5.15 MWC 300 (V431 Sct; IRAS 18267-0606; HBC 283; HIP 90617)

Both the distance and the spectral classification are very uncertain. We take a distance of 15.5 kpc and a spectral type Be, as reported by Leinert et al. (1997).

(Fig. 18). Our image shows a very crowded field, a stellar density peak with radius $r\sim 4$ pc (assuming a distance of 15.5 kpc) is possibly detected.

 

Figure 18:  MWC 300. Left: K-band image; right: K-band source surface density profile

5.16 RNO 1B

Yang et al. (1991) classify this star as a FU Orionis star, the distance is estimated to be 850 pc. The spectral classification is very uncertain (Be-type). The infrared source is coincident with an ammonia clump (Estarella et al. 1993) with a size of $0.5\times0.2$ pc and an estimated H₂ column density of 10$^{23}\rm\,\,cm^{-2}$. Anglada et al. (1994) report the detection of a group of compact radio sources, none of which is coincident with RNO 1B or RNO 1C, which are the brightest objects at 2.2 $\mu$m.

(Fig. 19). The star is surrounded by a bright extended nebulosity. Within the nebula a small group of stars with $r\sim 0.15$ pc is detected. The field stars surface density appears to increase away from the Herbig AeBe star, suggesting that localized extinction is present. The size of the cluster appears to be consistent with that of the ammonia clump detected by Estarella et al. 1993). The presence of localized dense molecular material could explain the lack of background stars close to the central object. However, the expected extinction provided by the molecular gas would prevent the detection of young stars embebbed inside the clump, thus the most plausible explanation is that a cluster of young stars is emerging from the observer's side of the cloud.

 

Figure 19:  RNO 1B. Left: K-band image; right: K-band source surface density profile

5.17 HD 259431  (BD+10$^\circ$1172; MWC 147; NGC 2247)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (800 pc) is from Finkenzeller & Mundt (1984) and the spectral type (B5) from Hillenbrand (1995).

The star is included in the Hipparcos data (van den Ancker 1988), however, only a lower limit to the distance (D>130 pc) is given. It is classified as a B1Ve star (with Log $T_{\rm eff}$ = 4.41 K) in Monoceros (associated with L 1605, NGC 2247 and Mon R1).

The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 480 $M_\odot$ in a region of = 0.8 pc size.

(Fig. 20). In our images the star appears to be isolated and surrounded by a faint infrared nebulosity.

 

Figure 20:  HD 259431. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.18 XY Per (HD 275877; ADS 2788; BD+38$^\circ$811)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (160 pc) is from Cohen (1973), and the spectral type (B6) from Finkenzeller & Mundt (1984). The distance is uncertain. Hipparcos data (van den Ancker et al. 1998) give a distance of 120⁺⁸⁸_-36 pc, A2II+B6e, Log($T_{\rm eff}$) = 4.15. NIR shift-and-add imaging finds a companion at 1.2'' (192 AU at the assumed distance) with no K magnitude difference between primary and companion (Pirzkal et al. 1997).

(Fig. 21). Although the field does not appear to be crowded, the source surface density profile reveals only a moderate enhancement of sources within $r\sim 0.08$ pc from the Herbig AeBe star.

 

Figure 21:  XY Per. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.19 LkH$\alpha$ 25 (HBC 219; V590 Mon; IRAS 06379+0950)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (800 pc) is from Finkenzeller & Mundt (1984) and the spectral type (B7) from Hillenbrand (1995). Hillenbrand et al. (1992) classify this star as a Group II star, and spectral type A0, while Finkenzeller & Mundt (1984) classify it as a B8 star.

(Fig. 22). Crowded field with several bright stars and faint diffuse nebulosity. A small group of stars is detected within $r\sim0.3$ pc from the Herbig AeBe star.

 

Figure 22:  LkH$\alpha$ 25. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.20 HD 250550  (BD+16$^\circ$974; MWC 789)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (700 pc) is from Finkenzeller & Mundt (1984), the spectral type (B7) from Hillenbrand et al. (1992).

The star is included in the Hipparcos data of van den Ancker et al. (1998), but only a lower limit to the distance (>110 pc) is given.

The star is not detected at 1.3 mm (Hillenbrand et al. 1992); the corresponding upper limit on the circumstellar mass is 0.13 $M_\odot$ in a region of 0.1 pc size. The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 140 $M_\odot$ in a region of 0.5 pc size. Higher resolution observations by Fuente et al. (1998) show that on a scale of 0.08 pc the amount of gas and dust is reduced to $\sim$5 $M_\odot$.

(Fig. 23). Close to the bright Herbig AeBe star there is a faint nebulosity to the north. No source density enhancement is detected.

 

Figure 23:  HD 250550. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.21 LkH$\alpha$ 215  (NGC 2245)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (800 pc) and spectral type (B7) from Finkenzeller & Mundt (1984).

Detected at submm wavelengths by Mannings (1994), who concluded from modelling of the SED that a second dust component in addition to an optically thick disk is required to explain the excess of emission at 450 $\mu$m.

The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=312\,\, M_\odot$ in a region of 0.5 pc size. Higher resolution observations by Fuente et al. (1998) show that on a scale of 0.08 pc the amount of gas and dust is reduced to $\sim$4 $M_\odot$.

(Fig. 24). A small group of stars is detected within $r\sim0.18$ pc from the Herbig AeBe star. The group is embedded in an arc shaped nebulosity.

 

Figure 24:  LkH$\alpha$ 215. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.22 LkH$\alpha$ 257 (HBC 312; IRAS 21523+4657)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (800 pc) and the spectral type (B8) are from Damiani et al. (1994).

Li et al. (1994) observed this source but reported no detection of companions or extended infrared emission.

(Fig. 25). In our large field infrared image, the stars in the field appear unevenly distributed, but no clear central peak is revealed in the source surface density profile.

 

Figure 25:  LkH$\alpha$ 257. Left: K-band image; right: K-band source surface density profile

5.23 BD+61$^\circ$154 (V594 Cas; IRAS 00403+6138; MWC 419; HIP 3401; HBC 330)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). Distance (650 pc) and spectral type (B8) are from Finkenzeller & Mundt (1984). The Hipparcos parallax of $3.3\pm 1.6$ mas (van den Anker 1998) yields a lower limit on the distance of D> 120 pc (which is consistent with the distance that we assume).

Hillenbrand et al. (1992) classify this as a Group I star. Li et al. (1994) observed the source to search for faint companions but their NIR images did not revealed any close companion or extended emission.

Millimeter observations by Hillenbrand et al. (1992) give a mass of about 0.16 $M_\odot$ in a region of about 0.1 pc size. The molecular survey of Hillenbrand (1995) yields an upper limit to the total mass of $M_{\rm cl}<$ 180 $M_\odot$ in a region of 0.2 pc size. Higher resolution observations by Fuente et al. (1998) show that on a scale of 0.08 pc the amount of gas and dust is reduced to $\sim$1 $M_\odot$.

(Fig. 26). The source surface density is uniform across the field (within the uncertainties), no density enhancement is detected around the Herbig AeBe star.

 

Figure 26:  BD+61$^\circ$154. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.24 VY Mon (HBC 202; IC 446)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance and spectral type that we adopt are from Damiani et al. (1994). The distance is that of the Monoceros OB1 association of which the star is assumed to be a member. The spectral type (B8) is from Thé et al. (1994).

(Fig. 27). A small group of stars within $r\sim 0.25$ pc is detected around the Herbig AeBe star. Some of the stars in the field show infrared excess and a consistent amount of extinction.

 

Figure 27:  VY Mon. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.25 VV Ser (HBC 282; IRAS 18262+0006)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (440 pc) and the spectral type (B9) that we assume are from Hillenbrand et al. (1992). However, spectral type (and distance) are rather uncertain. Finkenzeller & Mundt (1984) give B1/B3; Hamann & Persson (1992) B5; Chavarria-K et al. (1988) A2 and 240 pc. All these different classifications are based on spectra, but use different lines.

Li et al. (1994) observed the source in their NIR survey for faint companions. In the H-band contour plot that they show there are 6 stars within $\sim 15^{\prime\prime}$ from the Herbig AeBe star. However, in spite of the fact that the closest companion is at $\sim$3350 AU from the star, it is not detected in the search for close companions of Leinert et al. (1997), which should include all companions closer than 3600 AU.

The star is not detected in the millimeter (Hillenbrand et al. 1992). An estimate of the mass within 0.03 pc gives <0.025 $M_\odot$(Natta et al. 1997).

(Fig. 28). Our K-band image is completely consistent with the images of Li et al. (1994), and we detect all their six sources. A clear source surface density enhancement is detected around the star with $r\sim 0.1$ pc.

 

Figure 28:  VV Ser. Left: K-band image; right: K-band source surface density profile

5.26 V380 Ori  (BD-06$^\circ$1253; MWC 765; Haro 4-235)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (460 pc) and spectral type (B9) from Hillenbrand et al. (1992).

The Hipparcos parallax (van den Ancker et al. 1998) is not determined with sufficient accuracy to derive a reliable estimate of the distance of the object.

In their survey, Leinert et al. (1997) find a companion at 0.134'' (71 AU) with a luminosity of $\sim$50 $L_\odot$ (corresponding to another young intermediate mass star in the region).

There is a weak 1.3 mm emission associated to this star (Henning et al. 1994); the corresponding amount of circumstellar gas and dust is rather small (0.01 $M_\odot$ in a region of 0.05 pc size).

(Fig. 29). The Herbig AeBe star is surrounded by a diffuse nebulosity, which might prevent the detection of faint companions close to the star. The source surface density profile does not show any enhancement close to the central position. Many NIR excess and reddened stars are detected in the field.

 

Figure 29:  V 380 Ori. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.27 V 1012 Ori (HBC 431; IRAS 05090-0226)

To our knowledge, there is no measurements of V and (B-V) in the literature, hence it has not been possible to derive the stellar parameters as described above. The distance (460 pc) and spectral type (B9) are from Herbig & Bell (1988) catalogue.

(Fig. 30). Very few stars in the field, no group detected.

 

Figure 30:  V 1012 Ori. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.28 LkH$\alpha$ 218

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (1150 pc) is from Herbst et al. (1982) and spectral type (B9) from Hillenbrand et al. (1992).

(Fig. 31). Crowded field, no stellar density enhancement detected.

 

Figure 31:  LkH$\alpha$ 218. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.29 AB Aur (HD 31293; BD+30$^\circ$741; MWC 93)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (160 pc) from Finkenzeller & Mundt (1984), the spectral type (A0) from Cohen & Kuhi (1979).

The distance and physical parameters that we adopt are in agreement with the Hipparcos estimates: d=144 pc, Spectral type A0Ve+sh, Log($T_{\rm eff}$) = 4.00, Log$(L) = 1.72~L_\odot$ (van den Ancker 1997).

AB Aur is not resolved at 50 and 100 $\mu$m by Di Francesco et al. (1994). It is detected (Mannings 1994) at all submm wavelengths; from the 1.3 mm flux in a FWHM beam of 28$\hbox{$^{\prime\prime}$}$(Hillenbrand et al. 1992), Natta et al. (1997) derive a circumstellar mass of 0.013 $M_\odot$. Most of the matter is likely to be in a circumstellar disk, detected at 2.3 mm with the OVRO interferometer (Mannings & Sargent 1997).

(Fig. 32). AB Aur is an isolated very bright star with an extended halo detected in all our images.

 

Figure 32:  AB Aur. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.30 VX Cas (HBC 329; IRAS 00286+6142)

The V-magnitude, (B-V) colour and the spectral type (A0) are from Shevchenko et al. (1993). The distance (760 pc) is from Natta et al. (1997).

The star is not detected at 1.3 mm (Natta et al. 1997; $F_{\rm 1.3~mm}<$ 6 mJy).

(Fig. 33). Rather crowded field, a moderate density enhancement is detected around the Herbig AeBe star within $r\sim0.3$ pc.

 

Figure 33:  VX Cas. Left: K-band image; right: K-band source surface density profile

5.31 HD 245185 (V1271 Ori; BD+09$^\circ$880; HBC 451; IRAS 05324+0959)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The spectral type (A2) and distance (400 pc) that we assume is that of Hillenbrand et al. (1992).

Mannings (1994) reports a single-dish 1.3 mm flux of 44 mJy for this source, which corresponds to about 0.05 $M_\odot$.The star has also been detected in the 2.7 mm continuum by Mannings & Sargent (1997) with the OVRO interferometer, but not in the CO(1-0) line.

(Fig. 34). In our NIR images the field appears to be very crowded but without a clear density enhancement around the Herbig AeBe star.

 

Figure 34:  HD 245185. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.32 MWC 480 (HD 31648; HIP 23143; BD+29$^\circ$774)

The V-magnitude and the (B-V) colour are from the Hipparcos catalogue (van den Ancker et al. 1998). The distance (140 pc) and the spectral type (A2) are from Mannings et al. (1997).

The Hipparcos parallax give an estimate of the distance consistent with what we assume (131 pc).

Mannings & Sargent (1997) quote a single-dish 1.3 mm flux of 360 mJy, from which we estimate a mass of circumstellar gas and dust of the order of 0.05 $M_\odot$. They detect a compact continuum emission at 2.6 mm and CO source with the OVRO interferometer, that they interpret as evidence of a circumstellar disk. The presence of a circumstellar rotating gaseous disk is confirmed by the observations of Mannings et al. (1997).

(Fig. 35). No clear source surface density enhancement is detected.

 

Figure 35:  MWC 480. Left: K-band image; right: K-band source surface density profile

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (460 pc) and spectral type (A2) are from Hillenbrand et al. (1992).

Hipparcos data (van den Ancker 1998) give d>130 pc, AIIIe, Log($T_{\rm eff}$) = 3.93 K, Log$(L) \gt 0.40~L_\odot$, which are consistent with what we assume.

The star is detected at 1.3 mm by Natta et al. (1997), who measure a mass 0.03 $M_\odot$ in a region of size 0.02 pc.

(Fig. 36). Rather empty field, no density enhancement detected around the Herbig AeBe star.

 

Figure 36:  UX Ori. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.33 T Ori  (BD-05$^\circ$1329; MWC 763; Haro 4-123; NGC 1977 884)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (460 pc) is from Hillenbrand et al. (1992) and spectral type that we adopt (A2) from Hillenbrand (1995); however, Hillenbrand et al. (1992) give B9, whereas Finkenzeller & Mundt (1984) give A3.

It is known as an eclipsing and spectroscopy binary with a period of 14.3 days (Shevchenko & Vitrichenko 1994); Hillenbrand (1995) finds a companion at 2.2 $\mu$m 7.7'' away (3500 AU) (confirmed by Leinert et al. 1997), however, due to the high stellar enhancement of the field it is unclear whether it is a real companion; its estimated luminosity is $\sim2~L_\odot$ (typical of a low mass TTauri star).

Henning et al. (1994) measure a 1.3 mm flux of 88 mJy with a beam of 23$\hbox{$^{\prime\prime}$}$, which corresponds to 0.12 $M_\odot$ within a radius of 0.025 pc (Natta et al. 1997).

(Fig. 37). Large scale extended emission is clearly detected in all the NIR bands. There seems to be a general tendency of a higher stellar density toward the north-west of the Herbig AeBe star, however no clear density enhancement is detected around it.

 

Figure 37:  T Ori. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.34 IP Per (HD 278937; HBC 348; BD+32$^\circ$656; IRAS 03376+3222)

The V-magnitude, (B-V) colour and spectral type (A3) are from Herbig & Bell (1988). The distance of 350 pc attributed to this star assumes that it is a member of the Perseus I OB association (Wood et al. 1994).

(Fig. 38). Rather empty field, no stellar group is detected around the Herbig AeBe star.

 

Figure 38:  IP Per. Left: K-band image; right: K-band source surface density profile

5.35 LkH$\alpha$ 208  (NGC 2163)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). Both the distance (1000 pc) and the spectral type (A3) that we adopt are from Hillenbrand et al. (1992).

Leinert et al. (1997) found a comparatively close binary with a separation of 0.115$^{\prime\prime}$ (corresponding to 115 AU); its luminosity appears high ($\sim100~L_\odot$) but rather uncertain.

Millimeter observations (Natta et al. 1997) give an upper limit to the circumstellar mass <0.03 $M_\odot$ within 0.025 pc. However, the molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 640 $M_\odot$ in a region of $\sim$0.8 pc size.

(Fig. 39). The stellar surface density appears to be constant across the whole field. A number of stars show a consistent amount of extinction (as seen from the (J-H, H-K) colour-colour diagram).

 

Figure 39:  LkH$\alpha$ 208. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.36 MWC 758 (HD 36112; BD+25$^\circ$843; IRAS 05273+2517; HIP 25793)

The V-magnitude and the (B-V) colour are from the Hipparcos catalogue (van den Ancker et al. 1998). The distance and spectral type that we adopt are those reported by Mannings & Sargent (1997), who give A5 and D=150 pc.

Mannings & Sargent (1997) quote a single-dish 1.3 mm flux of 72 mJy, which corresponds to 0.01 $M_\odot$ of circumstellar gas and dust; their OVRO observations also detect compact continuum and CO emission which is likely to come from a circumstellar disk.

(Fig. 40). A stellar surface density enhancement with $r\sim 0.03$ pc is marginally detected.

 

Figure 40:  MWC 758. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.37 RR Tau (BD+26$^\circ$887a; HD 245906; IRAS 05363+2620; HBC 170; AS 103)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (800 pc) is from Finkenzeller & Mundt (1984) and the spectral type (A4) from Hillenbrand et al. (1992).

Millimeter continuum observations (Henning et al. 1994) give only an upper limit to the amount of circumstellar matter in the immediate surroundings of the star (<0.03 $M_\odot$ within a distance of 0.05 pc). However, the molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 240 $M_\odot$ in a region of $\sim$1.6 pc size.

(Fig. 41). In our NIR images, the field appears to be rather crowded, with no density enhancement.

 

Figure 41:  RR Tau. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.38 HK Ori  (MWC 497; MH$\alpha$ 265-13)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (460 pc) from Hillenbrand et al. (1992) and spectral type (A4) from Finkenzeller & Mundt (1984).

K-band speckle interferometry (Leinert et al. 1997) reveals a companion at 0.34$^{\prime\prime}$ (156 AU), which is probably a low mass young star.

There is no molecular gas left around HK Ori. Fuente et al. (1998) did not detect ¹³CO and CS emission, while 1.3 mm continuum observations provide an upper limit to the dust mass of <0.5 $M_\odot$ within 0.08 pc.

(Fig. 42). Our NIR observations are affected by large photometric uncertainties (see Paper I). No clear density enhancement detected around the star. The colour-colour diagram reveals a probable systematic offset in the photometry.

 

Figure 42:  HK Ori. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.39 MaC H12 (HBC 1; PP 1)

The distance (850 pc) and the spectral type (A5) that we adopt are from Cohen & Kuhi (1976).

Osterloh & Beckwith (1995) detect the source at 1.3 mm; from their 1.3 mm flux, we derive a mass of circumstellar matter of 0.2 $M_\odot$ in a region of 0.04 pc size.

(Fig. 43). Moderately crowded field, a small group of stars is marginally detected within $r\sim 0.15$ pc from the Herbig AeBe star.

 

Figure 43:  MaC H12. Left: K-band image; right: K-band source surface density profile

5.40 LkH$\alpha$ 198 (V633 Cas)

The V-magnitude and (B-V) colour that we use are from Shevchenko et al. (1993). The distance (600 pc) is from Chavarria-K. (1985), and the spectral type (A5) from Hillenbrand et al. (1992).

The mid-infrared companion found by Lagage et al. (1993) at 10 $\mu$m 6$^{\prime\prime}$ north of the optical source is also detected in the NIR (Li et al. 1994; Leinert et al. 1997). The projected separation of the binary is 3300 AU; the estimated luminosity of the companion is $\sim100~L_\odot$,thus it could be the third Herbig AeBe star in the system.

Natta et al. (1993), from 50 and 100 $\mu$m observations, infer the existence of a dusty envelope surrounding the star, with a mass of about 45 $M_\odot$ within 0.5 pc. Millimeter observations at 1.3 mm (Hillenbrand et al. 1992) and 2.7 mm (Di Francesco et al. 1997) reveal an extended source; the mass of dust and gas in a region of size 0.08 pc is about 1 $M_\odot$. The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 373 $M_\odot$ in a region of 0.4 pc size. Higher resolution observations by Fuente et al. (1998) show that on a scale of 0.08 pc the amount of gas and dust is reduced to $\sim$5 $M_\odot$.

(Fig. 44). The two bright Herbig AeBe stars LkH$\alpha$ 198 and V 376 Cas are embedded in a diffuse nebulosity detected in all the three NIR bands. Faint sources close to the bright stars are difficult to detect within the extended emission. The K-band source surface density increases away from the central stars, suggesting that either the diffuse emission or the increased extinction due to a compact molecular clump localized around the Herbig AeBe stars prevent the detection of background stars and, possibly, faint companions.

 

Figure 44:  LkH$\alpha$ 198. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

Support to this possibility comes from the submm continuum observations of Sandell & Weintraub (1994) who found an embedded source at the center of a molecular outflow. 2.7 mm observations of Di Francesco et al. (1997) indicate that this source is quite extended and may thus provide a substantial amount of spatially extended extinction.

5.41 Elias 1  (V892 Tau)

The V-magnitude and (B-V) colour are from Berrilli et al. (1992), the distance (160 pc) and spectral type (A6) are from Hillenbrand (1995).

Pirzkal et al. (1997) NIR imaging reveals a companion at 3.72'' (595 AU) with a K mag difference of 4.2 between primary and companion. The companion is also revealed in the speckle interferometry survey for binaries among Herbig AeBe stars of Leinert et al. (1997); they give the IR companion position 4'' (570AU) to the NE of the target star, fainter by 4-5 mag; its estimated luminosity is $0.4~L_\odot$. It is also detected in the radio continuum survey of Skinner et al. (1993), who agree that it is probably a low mass pre-main sequence star.

Hillenbrand et al. (1992) measure a 1.3 mm flux of 490 mJy with a beam FWHM of 28$\hbox{$^{\prime\prime}$}$, which corresponds approximately to 0.08 $M_\odot$ of dust and gas in a region of 0.02 pc size. Di Francesco et al. (1997) detect the star at 2.7 mm with the PdB interferometer within 1$^{\prime\prime}$ of the optical position.

(Fig. 45). Our NIR images show an almost empty field, with no stellar density enhancement detected. In our images the faint companion is completely hidden by the luminosity of the Herbig AeBe star.

 

Figure 45:  Elias 1. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.42 BF Ori  (BD-06$^\circ$06 1259; HBC 169; IRAS 05348-0636; Haro 4-229)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (460 pc) is from Hillenbrand et al. (1992) and the spectral type (A7) from Hillenbrand (1995); however, Hillenbrand et al. (1992) give F2, whereas Finkenzeller & Mundt (1984) give A/F. We decided to adopt A7 which represent a mean value of the various determinations.

Hipparcos data (van den Ancker 1998) give: $\pi$ = -0.7 mas, d> 210 pc, A5-6IIIe, Log($T_{\rm eff}$) = 3.90 K, Log$(L) \gt 0.56~L_\odot$, consistent with our assumptions.

BF Ori is detected at 1.3 mm by Natta et al. (1997), who estimate a total mass of 0.008 $M_\odot$ in a region of 0.05 pc size.

(Fig. 46). No clear density enhancement is detected, even though the brightest sources are located near the Herbig AeBe star.

 

Figure 46:  BF Ori. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

5.43 LkH$\alpha$ 233 (V 375 Lac; HBC 313)

The V-magnitude and (B-V) colour are from Shevchenko et al. (1993). The distance (880 pc) and the spectral type (A7) are from Finkenzeller & Mundt (1984).

The star is not detected at 1.3 mm (<40 mJy; Hillenbrand et al. 1992), which results into an estimate of the circumstellar mass in a region of 0.12 pc size of <0.2 $M_\odot$. The molecular survey of Hillenbrand (1995) yields a mass estimate of $M_{\rm cl}=$ 250 $M_\odot$ in a region of $\sim$1.0 pc size. High resolution observations by Fuente et al. (1998) show that on a scale of 0.08 pc the amount of gas and dust is reduced to $\sim$3.5 $M_\odot$.

(Fig. 47). Our K-band image show a low source surface density field, without a central enhancement. This result is consistent with what has been found by Hillenbrand (1995) in her search for young groups around Herbig AeBe stars.

 

Figure 47:  LkH$\alpha$ 233. Left: K-band image; right: K-band source surface density profile

5.44 Z CMa  (BD-11$^\circ$1760; HD 53179; MWC 165)

The distance (1150 pc) is from Hillenbrand et al. (1992) and spectral type F5. The spectral type classification is very uncertain and the values quoted in the literature span the range A0-F5. It is not wise to determine luminosity and age from the V-magnitude and the (B-V) colour.

(Fig. 49). In our images the bright star is surrounded by a strong diffuse emission. No density peak is detected around the star. The photometry is affected by the systematic uncertainties described in Paper I and an offset in the H band magnitudes is evident in the colour-colour diagram.

 

Figure 48:   Z CMa. Top left: J-band image; top right: K-band image; bottom left: colour-colour diagram; bottom right: K-band source surface density profile

 

Figure 49:  Adopted BCV vs. $T_{\rm eff}$ and (V-K) vs. $T_{\rm eff}$relations, top and bottom panel respectively. Filled triangles are from the M-dwarfs calibration of Bessel (1991), filled circles are a compilation from the various references given in the text, the dotted line is the linear interpolation that we have used