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# Evolution of the dust/gas environment around Herbig Ae/Be stars

Tie Liu11affiliation: Department of Astronomy, Peking University, 100871,
Beijing China<EMAIL_ADDRESS>, Huawei Zhang11affiliation: Department of
Astronomy, Peking University, 100871, Beijing China<EMAIL_ADDRESS>,
Yuefang Wu11affiliation: Department of Astronomy, Peking University, 100871,
Beijing China<EMAIL_ADDRESS>, Sheng-Li Qin22affiliation: I.
Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln,
Germany , Martin Miller22affiliation: I. Physikalisches Institut, Universität
zu Köln, Zülpicher Str. 77, 50937 Köln, Germany

###### Abstract

With the KOSMA 3-m telescope, 54 Herbig Ae/Be stars were surveyed in CO and
13CO emission lines. The properties of the stars and their circumstellar
environments are studied by fitting the SEDs. The mean line width of 13CO
(2-1) lines of this sample is 1.87 km s-1. The average column density of H2 is
found to be $4.9\times 10^{21}$ cm-2 for the stars younger than $10^{6}$ yr,
while drops to $2.5\times 10^{21}$ cm-2 for those older than $10^{6}$ yr. No
significant difference is found among the SEDs of Herbig Ae stars and Herbig
Be stars at the same age. The infrared excess decreases with age. The envelope
masses and the envelope accretion rates decease with age after $10^{5}$ yr.
The average disk mass of the sample is $3.3\times 10^{-2}~{}M_{\sun}$. The
disk accretion rate decreases more slowly than the envelope accretion rate. A
strong correlation between the CO line intensity and the envelope mass is
found.

Massive core:pre-main sequence-ISM: molecular-ISM: kinematics and dynamics-
ISM: jets and outflows-stars: formation

††slugcomment: Accepted to ApJ

##  1 Introduction

Although significant number of astrophysical processes such as outflow,
inflow, disk, rotation have been observed towards high-mass star formation
regions, it is still unclear whether high-mass stars form in the same way as
low-mass counterparts. Thus detail studies of the circumstellar environment of
young high-mass stars are especially important to understand their formation
and evolution processes. However, most of high-mass stars are far away from us
and deeply embedded in the clouds, which add to the difficulties of detailed
studies. Intermediate-mass (3-8 M☉) pre-main-sequence Herbig Ae/Be stars are
visible at optical and infrared wavelengths which share similar circumstellar
properties with massive stars, therefore will provide clues in understanding
the circumstellar structure of high-mass young stars. Additionally, since
Herbig Ae (HAe) stars are the precursors of vega-type systems, investigations
of their circumstellar environment are also important for planet formation
studies.

Hebig Ae/Be stars are still located in molecular clouds. More and more
observational evidences and detailed modeling of the spectral energy
distributions (SEDs) strongly suggest the presence of circumstellar disks
around Herbig Ae/Be stars (Hillenbrand et al., 1992; Chiang et al., 2001;
Dominik et al., 2003). To probe their surrounding gas properties especially to
investigate the outer part of the disk and determine the mass and grain
properties, millimeter observations are needed (Alonso-Albi et al., 2009).
Recently, a handful of disks around Herbig Ae/Be stars have been spatially and
spectrally resolved by optical and infrared (Boccaletti, 2003; Eisner, 2004;
Monnier et al., 2008; Murakawa, 2010; Perrin et al., 2006; Okamoto et al.,
2009), as well as millimeter and sub-millimeter interferometric observations
(Alonso-Albi et al., 2009; Fuente et al., 2006; Hamidouche, 2010; Matthews et
al., 2007; Öberg et al., 2010; Schreyer et al., 2008; Wang et al., 2008).
However, the number of disks well studied at millimeter and sub-millimeter
wavelengths is still very small, and more samples are needed. In addition, we
now have more multi-wavelength datasets, including long-wavelength bands, than
what were available for previous studies, enabling us to model their detail
structures including star-disk-envelope.

In this paper, we report the results from a survey towards 54 Herbig Ae/Be
stars using the KOSMA 3-m telescope in CO and 13CO emission lines. Together
with SED modeling, we investigate the properties of the circumstellar
environment around these Herbig Ae/Be stars and explore their evolution. Our
studies also provide a sample of Herbig Ae/Be stars surrounded by rich
dust/gas, which are ideal for further higher spatial resolution observations
by interferometers at millimeter and sub-millimeter wavelengths. The next
section is about sample selection, and Section 3 describes the observation.
The basic results are presented in Section 4, and more detailed discussions
are given in Section 5. In section 6, a summary is present.

##  2 Sample

In order to collect a complete sample, we surveyed 54 Herbig Ae/Be stars from
Thé et al. (1994) with declination $\delta>-20\arcdeg$ which are accessible to
KOSMA telescope. These sources cover a large age range from 104 yr to 107 yr,
which are very useful to study the evolution of Herbig Ae/Be stars and their
circumstellar environments. The basic parameters of these stars are listed in
Table 1. The distances and spectral types of these stars are mainly obtained
from Thé et al. (1994) and Manoj et al. (2006), and completed with the help of
the SIMBAD database, operated at CDS, Strasbourg, France. There are 27 Ae
stars, 24 Be stars and 3 Fe stars in this sample. The masses of 40 sources are
obtained from Manoj et al. (2006). The effective temperatures are assigned
from the spectral types and listed in the seventh column of Table 1.

##  3 Observations

The single-point survey observations in 12CO (2-1), 12CO (3-2), 13CO (2-1) and
13CO (3-2) were carried out between January and February 2010 using the KOSMA
3-m telescope at Gornergrat, Switzerland. The medium and variable resolution
acousto optical spectrometers with bandwidth of 300 and 655-1100 MHz at 230
and 345 GHz were used as backends. The spectral resolutions were 0.22 km/s and
0.29 km/s for 230 and 345 GHz, respectively. The beam width at 230 and 345 GHz
were 130$\arcsec$ and 82$\arcsec$, respectively. Dual channel SIS receiver for
230/345 GHz is used for frontend, with the typical system temperatures of
120/150 K for 230/345 GHz, respectively. The forward efficiency Feff was 0.93
and the corresponding main beam efficiencies Beff were 0.68 and 0.72 at 230
and 345 GHz, respectively. Pointing was frequently checked on planets and was
better than 10$\arcsec$. The integration time for each source was about 8
seconds using the total power observation mode. For the data analysis, the
GILDAS software package including CLASS and GREG was employed (Guilloteau &
Lucas, 2000).

##  4 Results

###  4.1 Survey results

All of the sample sources were surveyed in 12CO (2-1) and 12CO (3-2) lines
which have been successfully detected towards 41 out of the 54 sources.
However, due to the bad weather, only 28 of the 41 sources were surveyed in
13CO (2-1) and 13CO (3-2). Fig. 1 and Fig. 2 presents the spectra of all the
54 sources. The red and green lines represent 12CO (2-1) and 13CO (2-1),
respectively. For the sources not surveyed in 13CO emission, only 12CO (2-1)
spectra are presented.

For the 41 sources successfully detected in 12CO emission, we fitted these
observed lines with a Gaussian function and present the fitting parameters
including the $V_{LSR}$, line width (FWHM) and antenna temperature
$T_{A}^{\phantom{A}*}$ in Table 2. The systematic velocities of each source
are obtained by averaging the $V_{LSR}$ of 13CO (2-1) and 13CO (3-2) lines if
available. For the sources not surveyed in 13CO emission, the systematic
velocities are obtained by averaging the $V_{LSR}$ of 12CO (2-1) and 12CO
(3-2) lines. The derived systematic velocities are listed in the [col. 2] of
Table 3. The spectral profiles of these sources show rich properties. Together
with 13CO (2-1) lines, the profiles of 12CO (2-1) lines are identified and
listed in the last column of Table 2. There are 11 sources having multiple
components; 3 sources having flat tops; 5 sources showing red asymmetry
profile and 5 sources showing blue asymmetry profile. Additionally, 2 sources
are identified as blue profile, 1 source as red profile, and 1 source shows
self-absorption.

The intensity ratios of 12CO (2-1) and 13CO (2-1) are derived and listed in
the [col. 3] of Table 3. The 12CO (2-1) optical depth can be obtained from the
comparison of the observed 12CO (2-1) and 13CO (2-1) antenna temperature,
assuming [12CO]/[13CO]=89. The 12CO (2-1) lines are found to be always
optically thick with an average optical depth of 26.6. Since the 12CO is
optically thick, the excitation temperature $T_{ex}$ can be obtained according
to Garden et al. (1991):

$T_{r}=\frac{T_{A}^{*}}{\eta_{b}}=\frac{h\nu}{k}[\frac{1}{exp(h\nu/kT_{ex})-1}\frac{1}{exp(h\nu/kT_{bg})-1}]\times~{}f_{\nu}$
(1)

where $T_{bg}=2.73~{}K$ is the temperature of the cosmic background radiation,
$f_{\nu}=f_{82}=\frac{\Theta_{s}^{2}}{\Theta_{s}^{2}+82^{2}}$,
$f_{\nu}=f_{130}=\frac{\Theta_{s}^{2}}{\Theta_{s}^{2}+130^{2}}$ are the beam-
filling factors of the 12CO (3-2) and the 12CO (2-1), respectively. The source
size $\Theta_{s}$ and the excitation temperature $T_{ex}$ can be calculated
simultaneously from equ (1) using 12CO (2-1) and 12CO (3-2) data together. To
calculate the line ratios R3,2 of the 12CO (3-2) and the 12CO (2-1), beam
filling factor should be taken into account. The corrected line ratios R3,2
can be obtained from:
$R_{3,2}=f_{82,130}\cdot\frac{\int~{}T_{A}(12CO(3-2))dv}{\int~{}T_{A}(12CO(2-1))dv}$,
where $f_{82,130}=\frac{1+(82/\Theta_{s})^{2}}{1+(130/\Theta_{s})^{2}}$ and
$\Theta_{s}$ is the source size.

Assuming the 13CO (2-1) is optically thin, the optical depth and column
density of the 13CO can be straightforwardly obtained under local thermal
equilibrium (LTE) assumption. With the abundance ratio [H2]/[13CO]=$8.9\times
10^{5}$, the column density of H2 also can be calculated. For these sources
which have not been surveyed with the 13CO, the column densities of H2 are
firstly obtained from the 12CO (2-1) lines under the assumption that the 12CO
(2-1) emission is optically thin and [H2]/[12CO]=$10^{4}$, and then multiplied
by an optical depth correction factor $C_{\tau}=\tau/(1-e^{-\tau})$. The
optical depths of the 12CO (2-1) for those sources not surveyed in the 13CO
emission are assigned as 26.6, the average value obtained above. All the
results are collected in Table 3.

###  4.2 The SED

We have compiled the SEDs for 53 sources in the sample except MWC 614, which
has not enough data to use for modeling. The optical (UBV) data are from Manoj
et al. (2006), JHK fluxes from the 2MASS All-Sky Catalog of Point Sources,
IRAC and MIPS data from Harvey et al. (2007); Gutermuth et al. (2009), IRAS
data from the IRAS catalogue of Point Sources, MSX data from MSX6C Infrared
Point Source Catalog, AKAIR data from AKARI/IRC mid-IR all-sky Survey and
AKARI/FIS All-Sky Survey Point Source Catalogues, SCUBA 450 $\micron$ and 850
$\micron$ submillimeter data from Di Francesco et al. (2008), 1.3 mm continuum
data from Henning et al. (1994). We also collected sub-mm and mm data for some
sources from Mannings et al. (1994), Acke et al. (2004), Di Francesco et al.
(1997), and Alonso-Albi et al. (2009). Although not all the sources have data
at all the wavelength bands, there are still enough data for each source to be
used for fitting the SED.

The SEDs are then modeled using the online 2D-radiative transfer tool
developed by Robitaille et al. (2006), which has been successfully tested by
Robitaille et al. (2007), on a sample of low-mass YSOs and by Grave & Kumar
(2009) on high-mass protostars. The geometry in the models consists of a
central star surrounded by a flared accretion disk, a rotationally flattened
infalling envelope and bipolar cavities. The SED fitting tool uses 200,000 YSO
model SEDs (20,000 sets of physical parameters and 10 viewing angles). The
distance and visual extinction are the only two input parameters in the
fitting process. During the fitting process, all the model SEDs in the grid
are compared with the observed data, and the model SEDs that fit a source well
can be picked out within a specified limit on $\chi^{2}$. For each source, a
minimum of three data points that are of good quality are required by the SED
model tool. In our sample, all the 53 sources have at least ten such data
points, spreading over the wavelength region of 0.3 to 2600 $\micron$, which
can well constraint the models with least standard deviations (Robitaille et
al., 2007). However, the two input parameters of the distance and visual
extinction are far from fixed, which lead to the degeneracy of the models. In
our cases, we assumed 30% uncertainty for each of the distances obtained from
literatures, and varied the visual extinction Av from 0 to 30. Although the
best fit model has the least $\chi^{2}$ value, it may not actually represent
the data very well (Grave & Kumar, 2009). In order to find a representative
set of values for each source, all the models are accepted and analyzed, which
satisfy the criterion of $\chi^{2}-\chi_{best}^{2}<3\times n_{data}$, where
$n_{data}$ is the number of the data points. Fig. 3 and Fig. 4 shows the
observed SEDs and model SEDs with $\chi^{2}-\chi_{best}^{2}<3\times n_{data}$.
Following Grave & Kumar (2009), a weighted mean and standard deviation are
derived for all the parameters of each source, with the weights being the
inverse of the $\chi^{2}$ of each model. All the parameters derived are listed
in Table 4. The various columns in Table 4. are as follows: [col. 1] name of
the source;[col. 2] visual extinction; [col. 3] age of the star; [col. 4] mass
of the star; [col. 5] radius of the star; [col. 6] total luminosity of the
star; [col. 7] temperature of the star; [col. 8] envelope mass; [col. 9]
envelope accretion rate; [col. 10] disk mass ; [col. 11] disk inclination
angle; [col. 12] outer radius of the disk; [col. 13] disk accretion rate.

##  5 Discussion

###  5.1 The CO emission

The mean line width of the 13CO(2-1) lines of this sample is 1.87 km s-1 with
a standard deviation of 0.66 km s-1. This line width is similar to that of
intermediate-mass star formation regions ($\sim$2 km s-1) (Sun et al., 2006),
larger than that of low-mass star formation regions (1.3 km s-1) (Myers, Linke
& Benson, 1983), but much smaller than that of high-mass star formation
regions associated with IRAS sources (3.09 km s-1) (Wang et al., 2009; Wu et
al., 2003).

The average column density of H2 is found to be $4.9\times 10^{21}$ cm-2
before $10^{6}$ yr, while drops to $2.5\times 10^{21}$ cm-2 after $10^{6}$ yr.
As shown in the left panel of Fig.5, the optical depth of the 12CO(2-1) ranges
from 7.5 to 54 with an average value of 27.7 before $10^{6}$ yr, but the
optical depth drops below 26.6 (the average value in this sample) after
$10^{6}$ yr, with an average value of 22.5. The excited temperature of CO
ranges from 4.3 K to 33 K, with an average of 13.8 K. As shown in the right
panel of Fig.5, a decreased trend is found for the excited temperature with
age. The decrease of the optical depth and excitation temperature with age may
be due to the different gas dispersion mechanisms in which most of gas should
be dispersed by outflows and stellar winds at the early evolutionary stage of
the stars, and UV radiation and photodissociation play an important role in
further gas dispersion as the stars evolve (Fuente et al., 2002). Therefore
only less dense molecular gas with low excitation temperature existed in outer
envelope of late-type stars is observed at millimeter and submillimeter
wavelengths.

###  5.2 The properties of the stars

The ages of the sample stars spread from 103 yr to 107 yr. About 40% sample
stars are younger than 106 yr, and the others are older than 106 yr. The
average mass of the stars is $3.9\pm 2.2$ M☉. In the left panel of Fig.6, we
compare the masses derived from SED fitting to those obtained from Manoj et
al. (2006). The masses (Mmod) from the SED modeling are well coincident with
the masses (Mlit) obtained from literatures with a relationship of
Mmod=M${}_{lit}\pm$0.44, where the correlation coefficient r=0.64. Although
the masses derived from the SED fitting seems slightly higher than those from
literatures, they are found to agree with each other better than $\pm 0.3$
orders of magnitude. We also compare the effective temperatures of the stars
obtained from SED fitting to those corresponding to the spectral types. We
find the agreement of the effective temperatures obtained from the two
independent methods for 80% of the sample sources is better than $\pm 0.3$
orders of magnitude. The average effective temperature of the sample stars is
(1.1$\pm$0.6)$\times 10^{4}$ K. As shown in Fig.7, the mass-luminosity
function of the sample stars is found to be $Log(L_{*}/L_{\sun})=(3.08\pm
0.17)Log(M_{*}/M_{\sun})+(0.48\pm 0.10)$, with the correlation coefficient
r=0.93.

###  5.3 The evolution of the SED

Meeus et al. (2001) proposed that the SEDs of Herbig Ae/Be stars can be
divided into two groups based on the different mid-infrared excesses: Group I
sources with strong mid-infrared flux while Group II sources with weaker
infrared excesses. Acke et al. (2005) found most HAe stars belong to Group I
and most HBe stars belong to Group II. However, there may be an evolutionary
link between Group I and Group II sources. We display the SEDs of the HAe
stars and HBe stars in our sample in Fig.3 and Fig.4 ordered by age (age
increases from top-left to bottom-right panel), respectively. Firstly, we find
no significant difference among the SEDs of HAe stars and HBe stars at the
same age; secondly, it is clearly to see the infrared excess decreases with
age for both HAe stars and HBe stars. The dashed lines show the SEDs of the
stellar photosphere, including the effect of foreground extinction, from the
best-fitting model (Robitaille et al., 2006). As shown in the second column of
Table 4, the interstellar extinctions Av range from 0 to 12 mag in our sample
from the SED modeling. We find at early ages ($<10^{6}$ yr), the optical and
near-infrared fluxes of most of the HAe and HBe stars can not be simply fitted
by a stellar photosphere with interstellar extinction, while the older ones
($>10^{6}$ yr) can be well fitted, indicating huge amounts of circumstellar
dust/gas exist at early ages, which causes large extinction and infrared
excess. The shortest wavelength at which infrared excess is recognizable is
around 2 $\micron$. At early ages, the excess at sub-mm/mm regions is also
very significant and HAe stars seem to have stronger sub-mm/mm excess than HBe
stars at the same age.

###  5.4 The circumstellar envelopes and the disks

The left panel of Fig.8 gives the number distribution of the envelope mass and
presents the envelope mass as function of stellar age. There is no difference
in the distribution of the envelope masses between HAe stars and HBe stars.
The envelope masses of the HAe and HBe stars are larger than
$10^{-2}~{}M_{\sun}$ before $10^{6}$ yr, but smaller than $10^{-2}~{}M_{\sun}$
after $10^{6}$ yr. The envelope masses decease with age after $10^{5}$ yr
following the relationship:$Log(M_{env}/M_{\sun})=(-4.0\pm
0.5)Log(t/yr)+(22\pm 3.4)$, with the correlation coefficient r=0.74. The
number distribution of the envelope accretion rate and the envelope accretion
rate as function of stellar age are presented in the right panel of Fig.8. The
average envelope accretion rate for the Herbig Ae/Be stars younger than
$10^{6}$ yr is $2.5\times 10^{-5}$ M${}_{\sun}\cdot$yr-1. The envelope
accretion rate drops below $10^{-6}$ M${}_{\sun}\cdot$yr-1 after $10^{6}$ yr,
and 25 sources older than $10^{6}$ yr have zero envelope accretion rate, which
means those sources can be explained by disk-only sources without infalling
envelope. We also find the envelope accretion rate decease with age after
$10^{5}$ yr following the
relationship:$Log(\dot{M}_{env}/M_{\sun}~{}\cdot~{}yr^{-1})=(-2.4\pm
0.5)Log(t/yr)+(8.2\pm 3.0)$, with the correlation coefficient r=0.72.

From the left panel of Fig.9, it can be seen the disk masses locate at a
narrow range from $10^{-3}~{}M_{\sun}$ to $10^{-1}~{}M_{\sun}$ if neglecting
the three points with extremely small disk mass. The average disk mass is
$3.3\times 10^{-2}~{}M_{\sun}$, and the maximum one is $0.26~{}M_{\sun}$ from
AS 447. No obvious evolutionary pattern is found towards the disk masses. The
right panel of Fig. 9 shows the disk accretion rate as function of stellar
age. The average disk accretion rate is $5\times 10^{-8}$
M${}_{\sun}\cdot$yr-1. An average disk accretion rate of $3.6\times 10^{-7}$
M${}_{\sun}\cdot$yr-1 is found for those sources younger than $10^{6}$ yr,
which is much lower than the corresponding envelope accretion rate, suggesting
the envelopes dominate the accretion at early stages of star formation.
However, after $10^{6}$ yr, the envelope accretion halts ($\dot{M}_{env}\sim
0$), while the disk accretion rate remains $\sim 1.6\times 10^{-8}$
M${}_{\sun}\cdot$yr-1. Additionally, the disk accretion rate deceases with age
following the
relationship:$Log(\dot{M}_{disk}/M_{\sun}~{}\cdot~{}yr^{-1})=(-0.6\pm
0.1)Log(t/yr)+(3.5\pm 0.7)$, with the correlation coefficient r=0.6,
nevertheless the disk accretion rate deceases much more slowly than the
envelope accretion rate.

###  5.5 The relationship between CO gas and the envelope

Fig.10 presents the line intensity of the 12CO (2-1) and 12CO (3-2) as
function of stellar age. It can be seen the CO line intensities of most of the
sources younger than $10^{6}$ yr are larger than 10 K km s-1, and drop below
10 K km s-1 after $10^{6}$ yr. The evolution behaviors of CO line intensity is
very similar to that of envelope (see Fig.8), suggesting possible co-evolution
between the envelope and the CO gas. We plot the line intensity of the 12CO
(2-1) and the 12CO (3-2) as function of envelope mass in Fig.11. Exclude those
data with line intensities smaller than 1 K km s-1, which have low signal-to-
noise level or no detection of CO emission, the CO line intensity is well
correlated with the envelope mass. For 12CO (2-1), the relationship can be
fitted by a power-law:$Log(I_{CO(2-1)}/K~{}km~{}s^{-1})=(0.076\pm
0.017)Log(M_{env}/M_{\sun})+(1.129\pm 0.052)$, where the correlation
coefficient r=0.64. For 12CO(3-2), the relationship can also be fitted by a
power-law:$Log(I_{CO(3-2)}/K~{}km~{}s^{-1})=(0.098\pm
0.019)Log(M_{env}/M_{\sun})+(1.037\pm 0.066)$, with a correlation coefficient
r=0.64. It seems that CO gas is associated with the envelopes.

##  6 Summary

We have surveyed 54 Herbig Ae/Be stars using the KOSMA 3-m telescope in the CO
and the 13CO emission lines. Together with SED modeling, we have investigated
the properties of the circumstellar environments around those Herbig Ae/Be
stars and explored their evolutionary characteristics. The main findings of
this paper are as below:

(1).We have successfully detected CO emission towards 41 out of the 54
sources, and 28 of the 41 sources were surveyed in 13CO (2-1) and 13 CO(3-2).
The mean line width of the 13CO (2-1) line width of this sample is 1.87 km
s-1, which is similar to that of intermediate-mass star formation regions
($\sim$2 km s-1). The average column density of H2 is found to be $4.9\times
10^{21}$ cm-2 before $10^{6}$ yr, while drops to $2.5\times 10^{21}$ cm-2
after $10^{6}$ yr.

(2).The SEDs of 53 sources are compiled and modeled using the online
2D-radiative transfer tool. From the SED fitting, we find 40% sample stars are
younger than 106 yr, and the others are older than 106 yr. The average mass of
the stars is $3.9\pm 2.2$ M☉. The mass-luminosity function of the sample stars
can be described as $Log(L_{*}/L_{\sun})=(3.08\pm
0.17)Log(M_{*}/M_{\sun})+(0.48\pm 0.10)$.

(3).We find no significant difference among the SEDs of HAe stars and HBe
stars at the same age and the infrared excess decreases with age for both HAe
stars and HBe stars.

(4).The envelop masses decease with age after $10^{5}$ yr. The average envelop
accretion rate for the Herbig Ae/Be stars younger than $10^{6}$ yr is
$2.5\times 10^{-5}$ M${}_{\sun}\cdot$yr-1 and drops below $10^{-6}$
M${}_{\sun}\cdot$yr-1 after $10^{6}$ yr. In our sample 25 sources older than
$10^{6}$ yr have zero envelop accretion rate. The average disk mass of the
sample is $3.3\times 10^{-2}~{}M_{\sun}$. The disk accretion rate deceases
with age, but more slowly than the envelope accretion rate.

(5).The CO line intensities of most of the sources younger than $10^{6}$ yr
are larger than 10 K km s-1, and drop below 10 K km s-1 after $10^{6}$ yr. The
CO line intensity is well correlated with the envelope mass, suggesting
possible co-evolution between the envelope and the CO gas.

## Acknowledgment

This work was supported by the NSFC under grants No. 11073003, 10733030, and
10873019, and by the National key Basic Research Program (NKBRP) No.
2007CB815403.

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Table 1: Parameters of all the Herbig Ae/Be stars surveyed Name |  $\alpha$(J2000) |  $\delta$(J2000) | Distance | Spectral Type | M∗ | log(Teff)
---|---|---|---|---|---|---
| (h m s) | ($\arcdeg\arcmin\arcsec$) | (pc) |  | M☉ | log(K)
MacC H12 | 00 07 02.6 | 65 38 38.2 | 850 | A5 D |  | 3.91
LkHA 198 / V633casbbCircumstellar disks detected by millimeter and sub-millimeter interferometric observations (Alonso-Albi et al., 2009; Fuente et al., 2006; Hamidouche, 2010; Matthews et al., 2007; Öberg et al., 2010; Schreyer et al., 2008; Wang et al., 2008). | 00 11 26.0 | 58 49 29.1 | 600 | B9 D | 4.25 | 4.02
Vx Cas | 00 31 30.7 | 61 58 51.0 | 760 | A0 D | 3 | 3.98
RNO 6 | 02 16 30.1 | 55 22 57.0 | 1600 | B3 D | 5.99 | 4.27
IP Per | 03 40 47.0 | 32 31 53.7 | 350 | A6 D | 2 | 3.92
XY Per | 03 49 36.2 | 38 58 55.5 | 160 | A2IIv+ C | 2 | 3.91
V892 Taua,ba,bfootnotemark:  | 04 18 40.6 | 28 19 15.5 | 160 | B8 D |  $>$5.11 | 4.08
AB Aura,ba,bfootnotemark:  | 04 55 45.8 | 30 33 04.3 | 144 | A0Vpe C | 2.77 | 3.97
MWC 480a,ba,bfootnotemark:  | 04 58 46.3 | 29 50 37.0 | 131 | A3Ve D | 1.99 | 3.94
HD 35929 | 05 27 42.8 | -08 19 38.4 | 345 | F2III D | 3.41 | 3.84
HD 36112 | 05 30 27.5 | 25 19 57.1 | 205 | A5 IVe | 2.17 | 3.91
HD 245185 | 05 35 09.6 | 10 01 51.5 | 400 | A1 D | 2.07 | 3.97
T OriaaCircumstellar disks detected by optical or infrared observations (Boccaletti, 2003; Eisner, 2004; Monnier et al., 2008; Murakawa, 2010; Perrin et al., 2006; Okamoto et al., 2009). | 05 35 50.4 | -05 28 34.9 | 460 | A3V C | 3.34 | 3.98
CQ Taua,ba,bfootnotemark:  | 05 35 58.5 | 24 44 54.1 | 100 | F3 D | 1.5 | 3.83
V380 Ori | 05 36 25.4 | -06 42 57.7 | 510 | A1e D |  $>$4.93 | 3.97
V586 Ori | 05 36 59.3 | -06 09 16.4 | 510 | A2V C | 3 | 3.98
BF Ori | 05 37 13.3 | -06 35 00.6 | 430 | A5II-IIIev C | 2.5 | 3.95
HD37411 | 05 38 14.5 | -05 25 13.3 |  | B9Ve |  | 4.02
Haro 13A | 05 38 18.2 | -07 02 25.9 | 460 | Be |  |
V599 Ori | 05 38 58.6 | -07 16 45.6 | 360 | A5 D |  | 3.91
RR Tau | 05 39 30.5 | 26 22 27.0 | 800 | A2II-IIIe C | 4.26 | 3.98
V350 Ori | 05 40 11.8 | -09 42 11.1 | 460 | A1 D | 2.22 | 3.97
MWC 789 | 06 01 60.0 | 16 30 56.7 | 700 | B9 D | 4.13 | 4.02
LkHA 208 | 06 07 49.5 | 18 39 26.5 | 1000 | A7 D | 3.24 | 3.89
LkHA 339 | 06 10 57.8 | -06 14 37 | 830 | A1 D | 3.18 | 3.97
LkHA 215bbCircumstellar disks detected by millimeter and sub-millimeter interferometric observations (Alonso-Albi et al., 2009; Fuente et al., 2006; Hamidouche, 2010; Matthews et al., 2007; Öberg et al., 2010; Schreyer et al., 2008; Wang et al., 2008). | 06 32 41.8 | 10 09 33.6 | 800 | B6 D |  $>$5.43 | 4.15
R Mona,ba,bfootnotemark:  | 06 39 10 | 08 44 09.7 | 800 | B0 |  $>$5.11 | 4.08
V590 Mon | 06 40 44.6 | 09 48 02.1 | 800 | B7 D |  $<$3.35 | 4.11
GU CMa | 07 01 49.5 | -11 18 03.3 |  | B2Vne C |  | 4.34
HD 141569aaCircumstellar disks detected by optical or infrared observations (Boccaletti, 2003; Eisner, 2004; Monnier et al., 2008; Murakawa, 2010; Perrin et al., 2006; Okamoto et al., 2009). | 15 49 57.7 | -03 55 16.3 | 99 | A0Ve D | 2.18 | 3.98
VV Sera,ba,bfootnotemark:  | 18 28 47.9 | 00 08 39.8 | 330 | B6 D |  $>$5.43 | 4.15
MWC 300 | 18 29 25.7 | -06 04 37.1 | 650 | Bpe D |  |
AS 310 | 18 33 27 | -04 58 06 | 2500 | B1 |  $>$6 | 4.4
MWC 614 | 19 11 04.3 | 21 11 26 |  |  |  |
Par 21 | 19 29 00.8 | 09 38 46.7 | 300 | A5e |  | 3.91
V1295 AqlaaCircumstellar disks detected by optical or infrared observations (Boccaletti, 2003; Eisner, 2004; Monnier et al., 2008; Murakawa, 2010; Perrin et al., 2006; Okamoto et al., 2009). | 20 03 02.5 | 05 44 16.7 | 290 | A2IVe D | 3.03 | 3.95
V1685 CygaaCircumstellar disks detected by optical or infrared observations (Boccaletti, 2003; Eisner, 2004; Monnier et al., 2008; Murakawa, 2010; Perrin et al., 2006; Okamoto et al., 2009). | 20 20 28.2 | 41 21 51.6 | 980 | B3 D |  $>$5.99 | 4.27
Par 22 | 20 24 29.5 | 42 14 03.7 |  | A5 eV |  | 3.91
PV CepbbCircumstellar disks detected by millimeter and sub-millimeter interferometric observations (Alonso-Albi et al., 2009; Fuente et al., 2006; Hamidouche, 2010; Matthews et al., 2007; Öberg et al., 2010; Schreyer et al., 2008; Wang et al., 2008). | 20 45 53.9 | 67 57 38.9 | 500 | A5 D |  | 3.91
AS 442aaCircumstellar disks detected by optical or infrared observations (Boccaletti, 2003; Eisner, 2004; Monnier et al., 2008; Murakawa, 2010; Perrin et al., 2006; Okamoto et al., 2009). | 20 47 37.5 | 43 47 25.0 | 826 | B9 D |  | 4.02
LkHA 134 | 20 48 04.8 | 43 47 25.8 | 700 | B2 D |  $>$6 | 4.34
HD 200775aaCircumstellar disks detected by optical or infrared observations (Boccaletti, 2003; Eisner, 2004; Monnier et al., 2008; Murakawa, 2010; Perrin et al., 2006; Okamoto et al., 2009). | 21 01 36.9 | 68 09 47.8 | 429 | B2 Ve C |  $>$5.99 | 4.27
LkHA 324 | 21 03 54.2 | 50 15 10.2 | 780 | B8 D |  $>$5.11 | 4.08
HD 203024 | 21 16 03 | 68 54 52.1 |  | A D |  |
V645 Cyg | 21 39 58.2 | 50 14 21.2 | 3500 | A0 D |  $>$4.94 | 3.98
LkHA 234 | 21 43 02.3 | 66 06 29 | 1250 | B5 Vev |  $>$5.29 | 4.11
AS 477 / BD 46 | 21 52 34.1 | 47 13 43.6 | 1200 | B9.5Ve C |  $>$4.94 | 3.98
LkHA 257 | 21 54 18.8 | 47 12 09.7 | 900 | B5 D |  | 4.19
BH Cep | 22 01 42.9 | 69 44 36.5 | 450 | F5IV C | 1.73 | 3.81
SV Cep | 22 21 33.2 | 73 40 27.1 | 440 | A0 D | 2.5 | 3.98
V375 Lac | 22 34 41 | 40 40 04.5 | 880 | A4 D | 3.19 | 3.93
IL Cep | 22 53 15.6 | 62 08 45 | 725 | B2IV-Vne C |  | 4.34
MWC 1080a,ba,bfootnotemark:  | 23 17 25.6 | 60 50 43.6 | 2200 | B0eq D |  $>$6 | 4.48
LkHA 259 | 23 58 41.6 | 66 26 12.6 | 890 | A9 D |  | 3.87

Table 2: Observational Parameters of the lines Name |  13CO (2-1) |  |  13CO (3-2) |  | CO (2-1) |  | CO (3-2) | Notes
---|---|---|---|---|---|---|---|---
| VLSR | FWHM | T${}_{A}^{*}$ |  | VLSR | FWHM | T${}_{A}^{*}$ |  | VLSR | FWHM | T${}_{A}^{*}$ |  | VLSR | FWHM | T${}_{A}^{*}$ |
| (km s-1) | (km s-1) | (K) |  | (km s-1) | (km s-1) | (K) |  | (km s-1) | (km s-1) | (K) |  | (km s-1) | (km s-1) | (K) |
MacC H12 | $-4.82\pm 0.02$ | $1.67\pm 0.04$ | 2.64 |  | $-4.63\pm 0.07$ | $1.03\pm 0.16$ | 1.57 |  | $-5.05\pm 0.02$ | $2.30\pm 0.03$ | 6.98 |  | $-5.14\pm 0.04$ | $2.50\pm 0.09$ | 7.92 | flat top
LkHA 198 | $-0.25\pm 0.01$ | $2.25\pm 0.02$ | 3.00 |  | $-0.06\pm 0.03$ | $1.98\pm 0.06$ | 2.59 |  | $-0.14\pm 0.01$ | $3.07\pm 0.01$ | 6.84 |  | $-0.06\pm 0.02$ | $2.67\pm 0.05$ | 6.06 | wings
RNO 6 | $-36.20\pm 0.02$ | $1.59\pm 0.03$ | 1.50 |  | $-35.87\pm 0.04$ | $1.51\pm 0.10$ | 1.41 |  | $-36.31\pm 0.02$ | $2.34\pm 0.04$ | 2.81 |  | $-36.27\pm 0.09$ | $2.31\pm 0.21$ | 2.50 | flat top
XY Per | $-4.20\pm 0.07$ | $2.11\pm 0.18$ | 0.47 |  |  |  |  |  | $-4.87\pm 0.04$ | $3.28\pm 0.09$ | 2.23 |  | $-4.73\pm 0.10$ | $2.68\pm 0.30$ | 2.47 | red asy
V892 Tau | $7.40\pm 0.01$ | $1.33\pm 0.02$ | 2.14 |  | $6.98\pm 0.05$ | $1.49\pm 0.15$ | 1.12 |  | $7.09\pm 0.01$ | $2.92\pm 0.03$ | 4.14 |  | $6.89\pm 0.02$ | $2.31\pm 0.05$ | 3.64 | blue asy
AB Aur |  |  |  |  |  |  |  |  | $6.10\pm 0.01$ | $1.04\pm 0.01$ | 4.70 |  | $6.18\pm 0.01$ | $0.96\pm 0.02$ | 4.96 |
T Ori | $7.47\pm 0.01$ | $1.28\pm 0.03$ | 4.27 |  | $7.48\pm 0.03$ | $1.19\pm 0.06$ | 8.58 |  | $7.29\pm 0.21$ | $1.78\pm 0.21$ | 13.51 |  | $7.20\pm 0.01$ | $1.58\pm 0.01$ | 24.73 | three comp
| $10.83\pm 0.12$ | $2.50\pm 0.18$ | 2.76 |  | $11.15\pm 0.25$ | $1.99\pm 0.55$ | 3.07 |  | $10.42\pm 0.21$ | $3.07\pm 0.21$ | 14.38 |  | $10.34$ | $2.73\pm 0.03$ | 19.27 |
| $13.13\pm 0.16$ | $2.32\pm 0.25$ | 1.86 |  | $13.34\pm 0.62$ | $2.02\pm 0.84$ | 1.35 |  | $13.30\pm 0.21$ | $3.37\pm 0.21$ | 11.40 |  | $13.17$ | $3.42\pm 0.04$ | 14.13 |
V380 Ori | $6.99\pm 0.05$ | $1.35\pm 0.11$ | 2.34 |  | $6.93\pm 0.09$ | $0.82\pm 0.17$ | 1.85 |  |  |  |  |  |  |  |  |
| $8.95\pm 0.03$ | $2.14\pm 0.06$ | 6.44 |  | $9.02\pm 0.05$ | $2.03\pm 0.12$ | 5.60 |  | $8.85$ | $4.01\pm 0.02$ | 7.46 |  | $8.95\pm 0.02$ | $3.40\pm 0.05$ | 6.50 | two comp
V586 Ori |  |  |  |  |  |  |  |  | $6.54\pm 0.03$ | $1.77\pm 0.07$ | 2.18 |  | $6.54\pm 0.06$ | $1.93\pm 0.21$ | 1.70 | two comp
|  |  |  |  |  |  |  |  | $8.74\pm 0.01$ | $1.42\pm 0.02$ | 7.43 |  | $8.75\pm 0.01$ | $1.31\pm 0.03$ | 9.09 |
BF Ori | $6.59$ | $1.64\pm 0.05$ | 2.86 |  | $5.77\pm 0.07$ | $1.12\pm 0.16$ | 2.46 |  | $6.54\pm 0.21$ | $2.82\pm 0.21$ | 6.75 |  | $6.05\pm 0.04$ | $2.46\pm 0.06$ | 6.53 | three comp
| $9.17\pm 0.09$ | $1.82\pm 0.18$ | 1.49 |  |  |  |  |  | $9.14\pm 0.21$ | $2.32\pm 0.21$ | 3.98 |  | $8.77\pm 0.05$ | $2.75\pm 0.13$ | 4.36 |
| $10.89\pm 0.10$ | $1.22\pm 0.24$ | 0.88 |  |  |  |  |  | $10.70\pm 0.21$ | $1.56\pm 0.21$ | 1.79 |  | $10.40\pm 0.02$ | $1.22\pm 0.08$ | 1.32 |
Haro 13A | $5.78\pm 0.02$ | $2.10\pm 0.05$ | 2.38 |  | $5.47\pm 0.07$ | $1.01\pm 0.19$ | 2.17 |  | $5.71\pm 0.02$ | $3.62\pm 0.02$ | 6.00 |  | $5.19\pm 0.08$ | $2.92\pm 0.07$ | 5.14 | blue asy
V599 Ori | $5.02\pm 0.04$ | $2.40\pm 0.12$ | 1.35 |  | $5.07\pm 0.20$ | $2.73\pm 0.53$ | 0.67 |  | $5.25\pm 0.02$ | $3.51\pm 0.03$ | 4.78 |  | $4.94\pm 0.15$ | $3.49\pm 0.11$ | 3.24 | two comp?
| $7.18\pm 0.05$ | $1.24\pm 0.13$ | 0.77 |  |  |  |  |  |  |  |  |  |  |  |  |
RR Tau | $-5.40\pm 0.02$ | $1.36\pm 0.06$ | 1.55 |  | $-5.41\pm 0.04$ | $0.98\pm 0.10$ | 1.14 |  | $-5.09\pm 0.01$ | $1.83\pm 0.02$ | 5.22 |  | $-5.02\pm 0.01$ | $1.84\pm 0.02$ | 6.80 |
V350 Ori | $4.39\pm 0.06$ | $1.37\pm 0.16$ | 0.69 |  |  |  |  |  | $3.70\pm 0.04$ | $3.25\pm 0.06$ | 1.84 |  | $3.68\pm 0.05$ | $3.78\pm 0.41$ | 1.01 | blue profile
MWC 789 | $2.57\pm 0.08$ | $1.80\pm 0.20$ | 0.58 |  |  |  |  |  | $2.61\pm 0.02$ | $2.01\pm 0.04$ | 1.95 |  | $2.62\pm 0.05$ | $1.80\pm 0.12$ | 1.12 | blue asy
LkHA 208 | $-0.13\pm 0.04$ | $1.50\pm 0.08$ | 1.30 |  |  |  |  |  | $0.02\pm 0.03$ | $1.87\pm 0.07$ | 3.01 |  | $-0.04\pm 0.04$ | $1.21\pm 0.13$ | 2.53 | two comp
LkHA 339 | $11.57\pm 0.02$ | $3.08\pm 0.04$ | 2.97 |  | $11.03\pm 0.06$ | $2.27\pm 0.14$ | 2.49 |  |  |  |  |  |  |  |  | self-abs
LkHA 215 | $2.67\pm 0.02$ | $1.96\pm 0.05$ | 1.70 |  | $2.34\pm 0.03$ | $1.10\pm 0.07$ | 2.10 |  | $2.82\pm 0.02$ | $2.55\pm 0.04$ | 6.62 |  | $2.89\pm 0.05$ | $2.48\pm 0.13$ | 7.62 | red-asy
R Mon | $9.55\pm 0.04$ | $1.57\pm 0.09$ | 0.61 |  |  |  |  |  | $9.51\pm 0.02$ | $2.35\pm 0.06$ | 4.10 |  | $9.69\pm 0.08$ | $1.93\pm 0.07$ | 3.80 | red-asy
V590 Mon | $5.48\pm 0.04$ | $1.75\pm 0.09$ | 0.72 |  | $4.96\pm 0.12$ | $3.00\pm 0.34$ | 0.84 |  | $5.06\pm 0.03$ | $3.25\pm 0.06$ | 2.41 |  |  |  |  | three comp
| $9.02\pm 0.05$ | $1.61\pm 0.13$ | 0.68 |  | $8.76\pm 0.10$ | $1.74\pm 0.22$ | 0.83 |  | $8.93\pm 0.01$ | $2.02\pm 0.02$ | 6.37 |  | $8.95\pm 0.04$ | $1.93\pm 0.10$ | 6.74 |
| $11.48\pm 0.06$ | $1.78\pm 0.20$ | 0.56 |  | $11.38\pm 0.05$ | $1.31\pm 0.15$ | 1.33 |  | $11.45\pm 0.01$ | $1.58\pm 0.02$ | 4.99 |  | $11.53\pm 0.04$ | $1.52\pm 0.09$ | 5.87 |
VV Ser |  |  |  |  |  |  |  |  | $5.34$ | $1.73\pm 0.04$ | 1.14 |  | $5.38\pm 0.29$ | $1.43\pm 0.29$ | 0.77 | three comp
|  |  |  |  |  |  |  |  | $7.32\pm 0.01$ | $1.91\pm 0.04$ | 1.29 |  | $7.53\pm 0.29$ | $1.73\pm 0.29$ | 1.92 |
|  |  |  |  |  |  |  |  | $9.51\pm 0.01$ | $2.08\pm 0.04$ | 0.92 |  | $9.13\pm 0.29$ | $1.47\pm 0.29$ | 0.81 |
MWC 300 |  |  |  |  |  |  |  |  | $6.54\pm 0.21$ | $2.12\pm 0.21$ | 0.42 |  | $6.48\pm 0.13$ | $0.55\pm 0.21$ | 0.21 | three comp?
|  |  |  |  |  |  |  |  | $8.27\pm 0.21$ | $1.87\pm 0.21$ | 1.15 |  | $7.92\pm 0.06$ | $1.44\pm 0.20$ | 0.85 |
|  |  |  |  |  |  |  |  | $10.12\pm 0.21$ | $1.62\pm 0.21$ | 1.24 |  | $10.00\pm 0.08$ | $1.70\pm 0.19$ | 0.76 |
AS 310 |  |  |  |  |  |  |  |  | $7.07\pm 0.07$ | $2.15\pm 0.13$ | 0.53 |  | $7.28\pm 0.20$ | $1.90\pm 0.87$ | 0.54 |
MWC 614 |  |  |  |  |  |  |  |  | $2.22\pm 0.09$ | $1.10\pm 0.20$ | 0.39 |  |  |  |  |
Par 21 |  |  |  |  |  |  |  |  | $16.79\pm 0.04$ | $1.07\pm 0.09$ | 0.66 |  | $16.97\pm 0.07$ | $0.81\pm 0.15$ | 0.82 |
V1685 Cyg | $7.61\pm 0.02$ | $1.90\pm 0.05$ | 5.22 |  | $7.79\pm 0.03$ | $1.89\pm 0.07$ | 6.60 |  | $7.59\pm 0.02$ | $2.83\pm 0.06$ | 9.98 |  | $7.60\pm 0.07$ | $2.68\pm 0.22$ | 9.83 | two comp
|  |  |  |  |  |  |  |  | $12.64\pm 0.08$ | $3.27\pm 0.19$ | 2.86 |  |  |  |  |
Par 22 |  |  |  |  |  |  |  |  | $4.84$ | $3.17\pm 0.02$ | 8.04 |  | $5.00\pm 0.02$ | $2.90\pm 0.04$ | 7.69 | two comp?
|  |  |  |  |  |  |  |  | $9.21\pm 0.03$ | $2.90\pm 0.06$ | 1.61 |  | $9.51\pm 0.11$ | $3.14\pm 0.33$ | 1.34 |
PV Cep | $2.78\pm 0.07$ | $0.66\pm 0.16$ | 0.72 |  |  |  |  |  | $2.15\pm 0.03$ | $2.98\pm 0.06$ | 1.97 |  |  |  |  | red asy
AS 442 | $0.14\pm 0.04$ | $1.12\pm 0.09$ | 0.77 |  |  |  |  |  | $0.23\pm 0.01$ | $1.44\pm 0.04$ | 3.14 |  | $0.22\pm 0.03$ | $1.43\pm 0.09$ | 3.29 | red wing
LkHA 134 |  |  |  |  |  |  |  |  | $0.70\pm 0.02$ | $1.79\pm 0.04$ | 2.15 |  | $0.94\pm 0.03$ | $1.28\pm 0.08$ | 1.89 |
HD 200775 | $2.30\pm 0.02$ | $1.90\pm 0.05$ | 1.49 |  | $2.66\pm 0.14$ | $2.68\pm 0.38$ | 0.95 |  | $1.68\pm 0.01$ | $3.53\pm 0.01$ | 4.71 |  | $1.60\pm 0.03$ | $3.18\pm 0.06$ | 4.91 | blue asy
LkHA 324 |  |  |  |  |  |  |  |  | $-2.43\pm 0.03$ | $5.62\pm 0.07$ | 3.36 |  | $-2.17\pm 0.04$ | $5.13\pm 0.09$ | 3.96 | blue asy?
V645 Cyg | $-44.05\pm 0.07$ | $2.94\pm 0.15$ | 1.96 |  | $-43.52\pm 0.10$ | $1.45\pm 0.19$ | 3.89 |  | $-44.07\pm 0.03$ | $3.87\pm 0.07$ | 3.64 |  | $-43.88\pm 0.03$ | $2.88\pm 0.07$ | 4.93 |
LkHA 234 | $-10.40\pm 0.01$ | $2.15\pm 0.02$ | 5.14 |  | $-10.55\pm 0.03$ | $1.98\pm 0.08$ | 6.71 |  | $-10.11\pm 0.02$ | $3.85\pm 0.05$ | 10.58 |  | $-10.11\pm 0.02$ | $2.94\pm 0.05$ | 10.21 | red wing?
AS 477 |  |  |  |  |  |  |  |  | $6.54\pm 0.01$ | $2.74\pm 0.04$ | 3.83 |  | $6.66\pm 0.03$ | $2.12\pm 0.10$ | 4.41 | red asy?
BD46 | $6.25\pm 0.02$ | $1.39\pm 0.05$ | 2.21 |  | $6.89\pm 0.07$ | $1.21\pm 0.16$ | 2.37 |  | $6.70\pm 0.01$ | $2.30\pm 0.04$ | 3.54 |  | $6.71\pm 0.03$ | $1.97\pm 0.07$ | 3.44 | blue wing
BH Cep |  |  |  |  |  |  |  |  | $1.81\pm 0.07$ | $0.93\pm 0.16$ | 0.35 |  |  |  |  |
V375 Lac |  |  |  |  |  |  |  |  | $-0.18$ | $1.72\pm 0.01$ | 7.13 |  | $-0.28$ | $1.55\pm 0.01$ | 9.90 |
IL Cep | $-9.99\pm 0.03$ | $1.78\pm 0.08$ | 1.62 |  |  |  |  |  | $-10.13\pm 0.04$ | $2.95\pm 0.09$ | 1.72 |  | $-9.95\pm 0.09$ | $2.10\pm 0.24$ | 0.83 | flat top
MWC 1080 | $-30.52\pm 0.02$ | $4.47\pm 0.06$ | 1.91 |  | $-30.52\pm 0.05$ | $3.48\pm 0.14$ | 1.46 |  |  |  |  |  |  |  |  | red profile,wings
LkHA 259 | $-7.13\pm 0.06$ | $1.98\pm 0.13$ | 1.17 |  | $-6.04\pm 0.07$ | $1.45\pm 0.17$ | 2.27 |  |  |  |  |  |  |  |  | blue profile

Table 3: Derived parameters of the lines Name | VLSR | $\frac{{}^{12}co(2-1)}{{}^{13}co(2-1)}$ | $\tau_{13co(2-1)}$ | $\tau_{12co(2-1)}$ | Tex | $\Theta_{s}$ | $\frac{{}^{12}co(3-2)}{{}^{12}co(2-1)}$ | N${}_{H_{2}}$
---|---|---|---|---|---|---|---|---
| (km s-1) |  |  |  | (K) |  $(\arcsec$) |  | ($10^{21}$cm-2)
MacC H12 | -4.7 | 3.6 | 0.33 | 28.96 | 20.93 | 179 | 0.95 | 5.49
LkHA 198 | -0.2 | 3.1 | 0.39 | 34.66 | 15.76 | 530 | 0.68 | 5.89
RNO 6 | -36.0 | 2.8 | 0.44 | 39.32 | 10.20 | 230 | 0.77 | 3.06
XY Per | -4.2 | 7.4 | 0.15 | 12.92 | 11.24 | 133 | 0.64 | 1.55
V892 Tau | 7.2 | 4.2 | 0.27 | 24.20 | 12.05 | 310 | 0.64 | 2.76
AB Aur | 6.1 |  |  | 26.60 | 15.29 | 188 | 0.72 | 1.40
T Ori | 7.5 | 4.4 | 0.26 | 22.95 | 86.79 | 74 | 0.87 | 39.81
| 11.0 | 6.4 | 0.17 | 15.12 | 44.65 | 141 | 0.87 | 13.47
| 13.2 | 8.9 | 0.12 | 10.61 | 32.99 | 162 | 0.92 | 6.16
V380 Ori | 7.0 |  |  | 26.60 |  |  |  |
| 9.0 | 2.2 | 0.61 | 53.95 | 16.36 | 800 | 0.69 | 12.83
V586 Ori | 6.5 |  |  | 26.60 | 8.36 | 300 | 0.72 | 1.23
| 8.7 |  |  | 26.60 | 24.12 | 153 | 0.82 | 3.68
BF Ori | 6.2 | 4.1 | 0.28 | 24.88 | 17.12 | 285 | 0.72 | 4.42
| 9.2 | 3.4 | 0.35 | 31.00 | 14.57 | 164 | 1.00 | 3.59
| 10.9 | 2.6 | 0.49 | 43.21 | 7.55 | 300 | 0.54 | 1.66
Haro 13A | 5.6 | 4.3 | 0.26 | 23.56 | 14.25 | 600 | 0.68 | 4.11
V599 Ori | 5.0 | 5.2 | 0.21 | 19.01 | 11.43 |  | 0.70 | 2.66
| 7.2 |  |  | 26.60 |  |  |  |
RR Tau | -5.4 | 4.5 | 0.25 | 22.37 | 21.09 | 126 | 0.90 | 3.43
V350 Ori | 4.4 | 6.3 | 0.17 | 15.38 | 6.84 |  | 0.60 | 1.20
MWC 789 | 2.6 | 3.8 | 0.31 | 27.18 | 7.06 |  | 0.50 | 1.33
LkHA 208 | -0.1 | 2.9 | 0.42 | 37.63 | 10.05 | 290 | 0.45 | 2.28
LkHA 339 | 11.3 | 3.8 | 0.31 | 27.18 | $>12.7$ |  |  | $>7.53$
LkHA 215 | 2.5 | 5.1 | 0.22 | 19.42 | 20.66 | 170 | 0.86 | 4.08
R Mon | 9.6 | 10.1 | 0.10 | 9.28 | 12.58 | 250 | 0.61 | 0.91
V590 Mon | 5.2 | 6.2 | 0.18 | 15.65 | 10.16 |  |  | 1.08
| 8.9 | 11.8 | 0.09 | 7.88 | 18.24 | 207 | 0.83 | 1.09
| 11.4 | 7.9 | 0.14 | 12.05 | 17.88 | 152 | 0.82 | 1.26
VV Ser | 5.4 |  |  | 26.60 | 6.23 | 270 | 0.44 | 0.98
| 7.4 |  |  | 26.60 | 12.69 | 74 | 0.71 | 2.04
| 9.3 |  |  | 26.60 | 6.81 | 140 | 0.43 | 1.25
MWC 300 | 6.5 |  |  | 26.60 | 4.32 | 300 | 0.09 | 1.00
| 8.1 |  |  | 26.60 | 6.53 | 220 | 0.51 | 1.08
| 10.1 |  |  | 26.60 | 6.08 | 500 | 0.58 | 0.91
AS 310 | 7.2 |  |  | 26.60 | 6.47 | 95 | 0.55 | 1.24
MWC 614 | 2.2 |  |  | 26.60 | 4.56 |  |  | 0.35
Par 21 | 16.9 |  |  | 26.60 | 8.18 | 78 | 0.50 | 0.74
V1685 Cyg | 7.7 | 2.8 | 0.44 | 39.32 | 22.23 | 330 | 0.83 | 10.00
| 12.6 |  |  | 26.60 | 11.26 |  |  | 2.00
Par 22 | 4.9 |  |  | 26.60 | 18.75 | 340 | 0.83 | 5.64
| 9.4 |  |  | 26.60 | 7.84 | 200 | 0.74 | 1.92
PV Cep | 2.8 | 12.4 | 0.08 | 7.48 | 9.05 |  |  | 0.43
AS 442 | 0.1 | 5.2 | 0.21 | 19.01 | 12.40 | 165 | 0.77 | 1.11
LkHA 134 | 0.8 |  |  | 26.60 | 9.07 | 205 | 0.50 | 1.34
HD 200775 | 2.5 | 5.9 | 0.19 | 16.53 | 15.13 | 193 | 0.73 | 3.08
LkHA 324 | -2.3 |  |  | 26.60 | 14.55 | 135 | 0.71 | 7.11
V645 Cyg | -43.8 | 2.4 | 0.54 | 47.97 | 18.13 | 109 | 0.65 | 12.32
LkHA 234 | -10.5 | 3.7 | 0.32 | 28.04 | 22.56 | 390 | 0.66 | 10.13
AS477/BD46 | 6.6 | 2.7 | 0.46 | 41.17 | 15.10 | 147 | 0.59 | 4.68
BH Cep | 1.8 |  |  | 26.60 | 4.41 |  |  | 0.29
V375 Lac | -0.2 |  |  | 26.60 | 28.38 | 119 | 0.81 | 5.76
IL Cep | -10.0 | 1.8 | 0.81 | 72.17 | 6.51 |  | 0.30 | 5.34
MWC 1080 | -30.5 |  |  | 26.60 | $>11.8$ |  |  | $>7.19$
LkHA 259 | -6.6 |  |  | 26.60 | $>6.4$ |  |  | $>3.49$

Table 4: The SED fitting results Name | Av | log(Age) | M∗ | R∗ | log(L∗) | log(T∗) | log(Menv) | log$\dot{M}_{env}$) | log(M${}_{disk})$ | Incl | log(Rout) | log($\dot{M}_{disk}$)
---|---|---|---|---|---|---|---|---|---|---|---|---
| (mag) | log(yr) | (M☉) | (R☉) | log(L☉) | log(K) | log(M☉) | log(M☉yr-1) | log(M☉) | ($\arcdeg$) | log(AU) | log(M☉yr-1)
MacC H12 | $0.61\pm 0.57$ | $3.73\pm 0.32$ | $1.84\pm 0.16$ | $14.96\pm 2.44$ | $1.79\pm 0.13$ | $3.62$ | $0.32\pm 0.16$ | $-4.88\pm 0.07$ | $-1.74\pm 0.10$ | $18.19$ | $1.21\pm 0.32$ | $-6.55\pm 0.35$
LkHA 198 | $0.00$ | $3.07\pm 0.06$ | $3.84\pm 0.38$ | $29.95\pm 5.60$ | $2.42\pm 0.14$ | $3.62$ | $0.06\pm 0.35$ | $-4.56\pm 0.13$ | $-2.12\pm 0.63$ | $57.17\pm 24.78$ | $0.54\pm 0.16$ | $-5.33\pm 0.12$
Vx Cas | $1.48\pm 0.30$ | $6.66\pm 0.25$ | $3.62\pm 0.24$ | $2.22\pm 0.08$ | $2.17\pm 0.11$ | $4.13\pm 0.02$ | $-4.30\pm 0.54$ |  | $-2.55\pm 0.13$ | $41.80\pm 19.87$ | $3.00\pm 0.32$ | $-7.89\pm 0.46$
RNO 6 | $0.71\pm 0.65$ | $6.03\pm 0.07$ | $5.10\pm 0.42$ | $2.76\pm 0.08$ | $2.75\pm 0.12$ | $4.23\pm 0.02$ | $1.08\pm 0.10$ | $-8.47\pm 0.31$ | $-1.78\pm 0.23$ | $78.59\pm 2.92$ | $2.40\pm 0.21$ | $-6.79\pm 0.94$
IP Per | $0.00\pm 0.01$ | $5.71\pm 0.09$ | $2.17\pm 0.47$ | $5.03\pm 0.50$ | $1.09\pm 0.09$ | $3.67\pm 0.01$ | $-1.64\pm 0.44$ | $-5.62\pm 0.41$ | $-1.49\pm 0.35$ | $28.66\pm 9.47$ | $2.45\pm 0.25$ | $-6.85\pm 0.78$
V892 Tau | $6.44\pm 1.95$ | $6.50\pm 0.37$ | $2.50\pm 0.88$ | $4.04\pm 2.84$ | $1.81\pm 0.24$ | $3.98\pm 0.18$ | $-0.88\pm 0.38$ | $-5.62\pm 0.38$ | $-1.29\pm 0.30$ | $30.50\pm 9.53$ | $2.69\pm 0.35$ | $-7.14\pm 0.15$
XY Per | $3.06\pm 0.09$ | $6.99$ | $2.81$ | $1.93$ | $1.75$ | $4.06$ | $-5.71$ |  | $-2.02$ | $78.61\pm 2.92$ | $2.77$ | $-8.81$
AB Aur | $1.04$ | $5.14$ | $1.10$ | $6.73$ | $1.10$ | $3.62$ | $-1.33$ | $-5.65$ | $-2.12$ | $31.79$ | $2.15$ | $-7.34$
MWC 480 | $0.33\pm 0.35$ | $6.33\pm 0.16$ | $3.04\pm 0.33$ | $4.47\pm 1.10$ | $1.78\pm 0.92$ | $3.86\pm 0.19$ | $-6.13\pm 0.35$ |  | $-1.29\pm 0.25$ | $54.75\pm 19.35$ | $2.38\pm 0.25$ | $-6.36\pm 0.67$
HD 35929 | $0.24\pm 0.16$ | $6.36\pm 0.19$ | $3.10\pm 0.47$ | $5.19\pm 0.95$ | $1.81\pm 0.23$ | $3.85\pm 0.03$ | $-2.87\pm 0.36$ |  | $-4.87\pm 0.63$ | $56.30\pm 19.64$ | $3.61\pm 0.72$ | $-10.66\pm 0.71$
HD 36112 | $0.60\pm 0.04$ | $6.96\pm 0.05$ | $1.95\pm 0.05$ | $1.83\pm 0.05$ | $1.11\pm 0.02$ | $3.91$ | $-5.86\pm 0.44$ |  | $-1.78\pm 0.49$ | $35.05\pm 11.45$ | $2.58\pm 0.33$ | $-8.23\pm 0.14$
HD 245185 | $0.00$ | $6.13$ | $3.74$ | $5.68$ | $2.17$ | $3.93$ | $-6.84$ |  | $-1.41$ | $81.37$ | $2.29$ | $-7.19$
T Ori | $1.47\pm 0.16$ | $6.69\pm 0.28$ | $3.72\pm 0.51$ | $2.33\pm 0.31$ | $2.27\pm 0.18$ | $4.13\pm 0.04$ | $-5.42\pm 0.46$ |  | $-1.26\pm 0.51$ | $53.80\pm 15.54$ | $2.60\pm 0.71$ | $-6.54\pm 0.43$
CQ Tau | $2.31\pm 0.13$ | $6.85\pm 0.15$ | $2.82\pm 0.27$ | $2.07\pm 0.03$ | $1.78\pm 0.16$ | $4.04\pm 0.04$ | $-4.50\pm 0.32$ |  | $-2.03\pm 0.47$ | $47.41\pm 31.50$ | $2.67\pm 0.23$ | $-7.47\pm 0.54$
V380 Ori | $2.87\pm 1.42$ | $5.87\pm 0.11$ | $4.68\pm 0.05$ | $6.62\pm 2.95$ | $2.62\pm 0.21$ | $4.03\pm 0.13$ | $0.88\pm 0.21$ | $-5.66\pm 0.43$ | $-3.51\pm 0.29$ | $45.12\pm 18.54$ | $2.88\pm 0.39$ | $-8.52\pm 0.48$
V586 Ori | $1.00$ | $6.01$ | $3.86$ | $7.62$ | $1.93$ | $3.80$ | $-0.06$ | $-7.56$ | $-1.60$ | $81.37$ | $2.24$ | $-6.86$
BF Ori | $1.81\pm 0.31$ | $6.72\pm 0.17$ | $3.09\pm 0.31$ | $2.19\pm 0.29$ | $1.94\pm 0.16$ | $4.07\pm 0.04$ | $-4.60\pm 0.98$ |  | $-2.94\pm 0.57$ | $49.03\pm 21.24$ | $2.58\pm 0.53$ | $-8.08\pm 0.59$
HD37411 | $11.65$ | $6.63$ | $0.35$ | $1.04$ | $-0.15$ | $3.55$ | $-8.77$ |  | $-2.33$ | $63.26$ | $2.09$ | $-7.18$
Haro 13A | $0.00$ | $3.02$ | $3.47$ | $24.48$ | $1.34\pm 0.32$ | $3.63$ | $-0.25\pm 0.65$ | $-4.71$ | $-1.84$ | $64.16\pm 21.08$ | $0.67$ | $-5.62\pm 0.36$
V599 Ori | $2.94\pm 1.62$ | $5.64\pm 0.30$ | $1.83\pm 1.19$ | $5.29\pm 1.59$ | $1.20\pm 0.31$ | $3.65\pm 0.06$ | $-1.36\pm 0.52$ | $-5.76\pm 0.35$ | $-1.24\pm 0.27$ | $42.47\pm 24.22$ | $2.59\pm 0.46$ | $-6.71\pm 0.37$
RR Tau | $1.82\pm 0.27$ | $6.53\pm 0.28$ | $3.68\pm 0.42$ | $2.60\pm 0.49$ | $2.30\pm 0.17$ | $4.12\pm 0.03$ | $-5.71\pm 0.46$ |  | $-1.12\pm 0.24$ | $43.72\pm 19.52$ | $2.60\pm 0.32$ | $-6.41\pm 0.32$
V350 Ori | $1.69\pm 0.47$ | $6.73\pm 0.16$ | $2.73\pm 0.39$ | $2.05\pm 0.31$ | $1.75\pm 0.19$ | $4.03\pm 0.06$ | $-3.48\pm 0.39$ |  | $-2.52\pm 0.50$ | $43.21\pm 19.30$ | $3.39\pm 0.32$ | $-7.29\pm 0.73$
MWC 789 | $2.42\pm 0.77$ | $6.24\pm 0.17$ | $3.90\pm 0.37$ | $2.81\pm 0.29$ | $2.36\pm 0.10$ | $4.12\pm 0.02$ | $-6.47\pm 0.18$ |  | $-1.02\pm 0.13$ | $22.65\pm 6.39$ | $2.43\pm 0.05$ | $-6.49\pm 0.37$
LkHA 208 | $5.39\pm 0.09$ | $5.97$ | $4.23$ | $6.69$ | $2.32$ | $3.93$ | $-0.93$ | $-7.33$ | $-1.00$ | $55.80\pm 14.37$ | $3.06$ | $-7.71$
LkHA 339 | $2.96\pm 0.12$ | $6.60\pm 0.31$ | $3.42\pm 0.60$ | $2.25\pm 0.25$ | $2.17\pm 0.28$ | $4.11\pm 0.05$ | $-2.38\pm 0.76$ |  | $-1.78\pm 0.36$ | $40.20\pm 21.08$ | $3.73\pm 0.52$ | $-8.67\pm 0.38$
LkHA 215 | $1.34\pm 0.35$ | $5.74$ | $5.13$ | $8.46$ | $2.59$ | $3.95$ | $1.05$ | $-5.01$ | $-2.15$ | $46.40\pm 21.09$ | $3.65$ | $-9.19$
R Mon | $4.87$ | $4.24$ | $4.67$ | $24.59$ | $2.29$ | $3.64$ | $-0.61$ | $-4.56$ | $-1.95$ | $18.19$ | $1.55$ | $-6.97$
V590 Mon | $0.42\pm 0.15$ | $6.45\pm 0.54$ | $4.71\pm 0.20$ | $5.86\pm 3.12$ | $2.47\pm 0.04$ | $4.06\pm 0.15$ | $-1.86\pm 0.68$ | $-6.57\pm 0.73$ | $-2.25\pm 0.31$ | $84.45\pm 2.87$ | $3.03\pm 0.36$ | $-8.03\pm 0.31$
GU CMa | $0.42$ | $6.90$ | $3.14$ | $2.05$ | $1.93$ | $4.09$ | $-3.51$ |  | $-7.11$ | $49.46$ | $3.62$ | $-13.76$
HD 141569 | $0.26\pm 0.04$ | $6.93$ | $2.14$ | $1.74$ | $1.33$ | $3.97$ | $-2.99$ |  | $-4.81$ | $56.31\pm 23.40$ | $3.72$ | $-11.82$
VV Ser | $3.98\pm 0.25$ | $6.81\pm 0.20$ | $3.32\pm 0.35$ | $2.16\pm 0.15$ | $2.10\pm 0.18$ | $4.10\pm 0.03$ | $-5.83\pm 0.63$ |  | $-1.39\pm 0.31$ | $45.71\pm 15.48$ | $2.72\pm 0.28$ | $-6.43\pm 0.34$
MWC 300 | $4.23\pm 2.13$ | $6.56\pm 0.11$ | $7.37\pm 0.67$ | $3.33\pm 0.19$ | $3.35\pm 0.13$ | $4.33\pm 0.03$ | $-6.44\pm 0.38$ |  | $-1.05\pm 0.01$ | $62.27\pm 13.03$ | $2.27\pm 0.23$ | $-5.80\pm 0.80$
AS 310 | $6.65\pm 3.01$ | $5.85\pm 0.21$ | $9.86\pm 0.53$ | $3.90\pm 0.10$ | $3.79\pm 0.09$ | $4.41\pm 0.01$ | $1.61\pm 0.08$ | $-4.31\pm 0.9$ | $-0.59\pm 0.11$ | $87.13$ | $3.26\pm 0.44$ | $-5.53\pm 0.80$
Par 21 | $1.61$ | $6.13$ | $3.74$ | $5.68$ | $2.17$ | $3.93$ | $-6.84$ |  | $-1.41$ | $87.13$ | $2.29$ | $-7.19$
V1295 Aql | $0.36$ | $6.69\pm 0.30$ | $3.22\pm 0.37$ | $2.29\pm 0.34$ | $2.00\pm 0.18$ | $4.07\pm 0.01$ | $-6.67\pm 0.30$ |  | $-2.55\pm 0.31$ | $66.45\pm 9.44$ | $1.55\pm 0.09$ | $-7.18\pm 0.53$
V1685 Cyg | $1.35\pm 0.95$ | $4.93\pm 0.37$ | $6.75\pm 1.40$ | $24.50\pm 12.49$ | $3.08\pm 0.14$ | $3.85\pm 0.13$ | $1.30\pm 0.24$ | $-4.08\pm 0.32$ | $-1.04\pm 0.35$ | $35.64\pm 14.64$ | $1.74\pm 0.34$ | $-4.61\pm 0.38$
Par 22 | $3.67\pm 2.57$ | $5.35\pm 0.35$ | $1.29\pm 1.14$ | $6.46\pm 2.88$ | $1.24\pm 0.34$ | $3.59\pm 0.09$ | $-0.06\pm 0.48$ | $-4.21\pm 0.55$ | $-1.71\pm 0.35$ | $54.82\pm 29.65$ | $2.00\pm 1.47$ | $-6.35\pm 0.52$
PV Cep | $3.16\pm 0.43$ | $3.08\pm 0.06$ | $0.28\pm 0.09$ | $5.69\pm 0.25$ | $1.77\pm 0.18$ | $3.51\pm 0.03$ | $-0.49\pm 0.19$ | $-5.33\pm 0.06$ | $-1.53\pm 0.34$ | $18.19$ | $0.30\pm 0.16$ | $-4.40\pm 0.06$
AS 442 | $1.98\pm 0.24$ | $6.54\pm 0.22$ | $4.31\pm 0.37$ | $2.67\pm 0.60$ | $2.48\pm 0.15$ | $4.17\pm 0.04$ | $-3.41\pm 0.61$ |  | $-1.99\pm 0.39$ | $55.67\pm 13.68$ | $2.92\pm 0.45$ | $-6.99\pm 0.47$
LkHA 134 | $2.67\pm 0.11$ | $6.27\pm 0.13$ | $4.13\pm 0.31$ | $2.67\pm 0.36$ | $2.45\pm 0.14$ | $4.16\pm 0.02$ | $-2.07\pm 0.06$ | $-8.05\pm 0.50$ | $-1.75\pm 0.26$ | $58.33\pm 20.25$ | $3.90\pm 0.20$ | $-9.06\pm 0.52$
HD 200775 | $0.12\pm 0.08$ | $5.34\pm 0.01$ | $6.65\pm 0.09$ | $14.22\pm 0.06$ | $2.78\pm 0.03$ | $3.88\pm 0.01$ | $1.61\pm 0.05$ | $-3.59\pm 0.30$ | $-2.33\pm 0.01$ | $26.17\pm 11.03$ | $1.93\pm 0.12$ | $-7.86\pm 0.11$
LkHA 324 | $1.01\pm 1.09$ | $6.16\pm 1.27$ | $2.32\pm 0.77$ | $4.87\pm 1.24$ | $1.47\pm 0.43$ | $3.76\pm 0.20$ | $-1.50\pm 0.51$ | $-5.54\pm 0.42$ | $-1.89\pm 0.45$ | $41.68\pm 19.41$ | $2.67\pm 0.97$ | $-7.74\pm 0.56$
HD 203024 | $0.45\pm 0.30$ | $6.89\pm 0.07$ | $2.35\pm 0.15$ | $1.89\pm 0.06$ | $1.48\pm 0.09$ | $3.99\pm 0.03$ | $-5.33\pm 0.36$ |  | $-2.06\pm 0.02$ | $74.29\pm 4.39$ | $2.27\pm 0.26$ | $-8.20\pm 0.30$
V645 Cyg | $0.42$ | $5.16$ | $10.59$ | $4.16$ | $3.88$ | $4.42$ | $2.46$ | $-3.38$ | $-2.26$ | $18.19$ | $2.96$ | $-7.44$
LkHA 234 | $3.05\pm 3.29$ | $5.15\pm 0.02$ | $8.96\pm 0.25$ | $4.91\pm 0.39$ | $3.76\pm 0.01$ | $4.35\pm 0.02$ | $2.82\pm 0.06$ | $-2.97\pm 0.05$ | $-0.79\pm 0.72$ | $45.13\pm 4.01$ | $2.21\pm 0.47$ | $-5.34\pm 1.02$
AS 477 | $0.60\pm 0.25$ | $6.43\pm 0.22$ | $5.11\pm 0.66$ | $2.72\pm 0.23$ | $2.76\pm 0.20$ | $4.22\pm 0.04$ | $-5.86\pm 0.45$ |  | $-1.65\pm 0.34$ | $59.44\pm 13.66$ | $2.55\pm 0.36$ | $-6.27\pm 0.35$
LkHA 257 | $2.62\pm 0.83$ | $6.62\pm 0.16$ | $3.61\pm 0.64$ | $2.68\pm 1.60$ | $2.18\pm 0.16$ | $4.11\pm 0.09$ | $-2.31\pm 0.66$ | $-6.99\pm 0.70$ | $-2.46\pm 0.71$ | $57.05\pm 22.40$ | $3.43\pm 0.34$ | $-7.14\pm 0.71$
BH Cep | $0.80\pm 0.34$ | $6.61\pm 0.29$ | $3.27\pm 0.21$ | $3.35\pm 1.33$ | $2.05\pm 0.13$ | $4.03\pm 0.06$ | $-3.49\pm 0.33$ |  | $-2.50\pm 0.70$ | $84.26\pm 2.88$ | $3.53\pm 0.14$ | $-8.24\pm 0.96$
SV Cep | $2.37\pm 0.17$ | $6.71\pm 0.17$ | $3.33\pm 0.48$ | $2.12\pm 0.18$ | $2.07\pm 0.24$ | $4.10\pm 0.04$ | $-6.40\pm 0.54$ |  | $-2.32\pm 0.42$ | $48.85\pm 22.50$ | $2.31\pm 0.36$ | $-7.55\pm 0.68$
V375 Lac | $1.85\pm 1.14$ | $3.71\pm 0.40$ | $1.88\pm 0.51$ | $15.15\pm 2.93$ | $1.92\pm 0.16$ | $3.62\pm 0.01$ | $0.55\pm 0.79$ | $-4.45\pm 0.15$ | $-1.28\pm 0.75$ | $18.19$ | $0.85\pm 0.32$ | $-5.18\pm 0.48$
IL Cep | $0.28\pm 0.32$ | $6.02\pm 0.10$ | $3.85\pm 0.19$ | $7.53\pm 1.07$ | $1.94\pm 0.15$ | $3.81\pm 0.07$ | $-2.43\pm 0.61$ | $-7.08\pm 0.54$ | $-2.54\pm 0.68$ | $47.87\pm 18.62$ | $2.47\pm 0.45$ | $-8.25\pm 0.34$
MWC 1080 | $1.01\pm 0.78$ | $5.37\pm 0.02$ | $10.59\pm 0.87$ | $4.00\pm 0.19$ | $3.88\pm 0.12$ | $4.43\pm 0.02$ | $2.08\pm 0.17$ | $-3.58\pm 0.21$ | $-1.01\pm 0.47$ | $38.03\pm 4.59$ | $2.72\pm 0.30$ | $-5.92\pm 0.37$
LkHA 259 | $1.78\pm 0.19$ | $3.29\pm 0.26$ | $2.63\pm 0.75$ | $22.94\pm 5.25$ | $2.19\pm 0.22$ | $3.61$ | $1.02\pm 0.15$ | $-3.09\pm 0.14$ | $-1.69\pm 0.32$ | $18.19$ | $0.59\pm 0.14$ | $-5.50\pm 0.28$
Figure 1: 12CO (2-1) (red) and 13CO (2-1) (green) lines of the A Type stars.
The source names are plotted in the upper-left corner of each panel.

Figure 2: 12CO (2-1) (red) and 13CO (2-1) (green) lines of the B/F Type stars.
The source names are plotted in the upper-left corner of each panel.

Figure 3: The SEDs of A Type stars. The observed data are plotted as circular
symbols. The black solid line represents the best fit to the data, while the
grey solid lines represent the fits with $\chi^{2}-\chi_{best}^{2}<3\times
n_{data}$. The dashed lines represent photospheric contributions, including
the effect of foreground extinction, from the best-fitting models. As shown by
the vertical lines, some model SEDs are with bad signal-to-noise ratios for
wavelengths beyond 1-100 $\micron$ (Robitaille et al., 2006).

Figure 4: The SEDs of B/F Type stars. The symbols and lines are the same as in
Fig.3

Figure 5: The optical depth $\tau$ (left) of 12CO (2-1) and the excited
temperature Tex (right) as function of the age. The horizonal and vertical
dashed lines in the left panel mark age at 106 yr and the average optical
depth of 26.6.

Figure 6: The masses derived from SED fitting compared to those obtained from
Manoj et al. (2006) (left) and the effective temperatures of the stars
obtained from SED fitting compared to the effective temperatures corresponding
to the spectral types (right). The solid lines in both panels describe the
least-square fitting. The dashed line in the left panel shows that Mmod is
consistent with Mlit. The two dashed lines in the right panel mark out the
area where the effective temperatures obtained from the two independent
methods agree better than $\pm$0.3 orders of magnitude. Figure 7: The mass-
luminosity function of the sample stars. The solid line represents the best
least-square fitting.

Figure 8: The envelope mass (left) and the envelope accretion rate (right) as
function of the age. The solid lines represent the best least-square fitting.
The vertical dashed lines mark age at 105 and 106 yr. The horizonal dashed
line in the left and right panels mark the envelope mass of 10-2 M☉ and the
envelope accretion rate of 10-6 M☉yr-1, respectively. The dashed oval in the
right panel marks the sources with zero envelope accretion rate.

Figure 9: The disk mass (left) and the disk accretion rate (right) as function
of the age. The solid lines represent the best least-square fitting.

Figure 10: The 12CO (2-1) intensity (left) and the 12CO (3-2) intensity
(right) as function of the age. The vertical and horizonal dashed lines are at
age equalling 106 yr and 12CO intensity corresponding to 10 K km s-1,
respectively. The dashed ellipses encircle the sources with low signal-to-
noise level in CO emission.

Figure 11: The 12CO (2-1) intensity (left) and the 12CO (3-2) intensity
(right) as function of the envelope mass. The solid lines represent the best
least-square fitting. The horizonal dashed line in the right panel is at where
12CO intensity corresponds to 10 K km s-1.The sources with low signal-to-noise
level in CO emission are shown in the dashed ellipses.