THE HERSCHEL ORION PROTOSTAR SURVEY: SPECTRAL ENERGY DISTRIBUTIONS
AND FITS USING A GRID OF PROTOSTELLAR MODELS
E. Furlan
1
, W. J. Fischer
2,14
, B. Ali
3
, A. M. Stutz
4
, T. Stanke
5
, J. J. Tobin
6,15,16
, S. T. Megeath
7
, M. Osorio
8
,
L. Hartmann
9
, N. Calvet
9
, C. A. Poteet
10
, J. Booker
7
, P. Manoj
11
, D. M. Watson
12
, and L. Allen
13
1
Infrared Processing and Analysis Center, California Institute of Technology, 770 S. Wilson Ave., Pasadena, CA 91125, USA; furlan@ipac.caltech.edu
2
Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
3
Space Science Institute, 4750 Walnut Street, Boulder, CO 80301, USA
4
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
5
ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany
6
National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
7
Ritter Astrophysical Research Center, Department of Physics and Astronomy, University of Toledo, 2801 W. Bancroft Street, Toledo, OH 43606, USA
8
Instituto de Astrofísica de Andalucía, CSIC, Camino Bajo de Huétor 50, E-18008 Granada, Spain
9
Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109, USA
10
New York Center for Astrobiology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180, USA
11
Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
12
Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA
13
National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719, USA
Received 2015 August 21; accepted 2016 February 21; published 2016 May 6
ABSTRACT
We present key results from the Herschel Orion Protostar Survey: spectral energy distributions (SEDs) and model
fits of 330 young stellar objects, predominantly protostars, in the Orion molecular clouds. This is the largest sample
of protostars studied in a single, nearby star formation complex. With near-infrared photometry from 2MASS, mid-
and far-infrared data from Spitzer and Herschel, and submillimeter photometry from APEX, our SEDs cover
1.2–870 μm and sample the peak of the protostellar envelope emission at ∼100 μm. Using mid-IR spectral indices
and bolometric temperatures, we classify our sample into 92 Class 0 protostars, 125 Class I protostars, 102 flat-
spectrum sources, and 11 Class II pre-main-sequence stars. We implement a simple protostellar model (including a
disk in an infalling envelope with outflow cavities) to generate a grid of 30,400 model SEDs and use it to determine
the best-fit model parameters for each protostar. We argue that far-IR data are essential for accurate constraints on
protostellar envelope properties. We find that most protostars, and in particular the flat-spectrum sources, are
wellfit. The median envelope density and median inclination angle decrease from Class 0 to Class I to flat-
spectrum protostars, despite the broad range in best-fit parameters in each of the three categories. We also discuss
degeneracies in our model parameters. Our results confirm that the different protostellar classes generally
correspond to an evolutionary sequence with a decreasing envelope infall rate, but the inclination angle also plays a
role in the appearance, and thus interpretation, of the SEDs.
Key words: circumstellar matter – infrared: stars – methods: data analysis – stars: formation – stars: protostars
Supporting material: figure set, machine-readable tables
1. INTRODUCTION
The formation process of low- to intermediate-mass stars is
divided into several stages, ranging from the deeply embedded
protostellar stage to the period when a young star is dispersing
its protoplanetary disk in which planets may have formed.
During the protostellar phase, which is estimated to last
∼0.5 Myr (Evans et al. 2009; Dunham et al. 2014), the growing
central source accretes dust and gas from a collapsing
envelope. The material from the envelope is most likely
accreted through a disk, feeding the growing star. A fraction of
the mass is ejected in outflows, which carve openings into the
envelope along the outflow axis. Despite our understanding of
the basic processes operating in low-mass protostars, funda-
mental questions remain (e.g., Dunham et al. 2014).In
particular, it is not understood how the processes of infall,
feedback from outflows, disk accretion, and the surrounding
birth environmentaffect mass accretion and determine the
ultimate stellar mass. The luminosity of protostars, which can
be dominated by accretion, is observed to span more than three
orders of magnitude, yet the underlying physics of this
luminosity range is also not understood ( Dunham et al.
2010;
Offner & McKee 2011). It is in this protostellar phase that disks
are formed, setting the stage for planet formation, yet how
infall, feedback, accretion, and environment influence the
properties of disks and of planets that eventually form from
them is unknown. The large samples of well-characterized
protostars identified from surveys with Spitzer and Herschel
now provide the means to systematically study the processes
controlling the formation of stars and disks; the goal of this
work is to provide such a characterization for the protostars
found in the Orion A and B clouds, the largest population of
protostars for any of the molecular clouds within 500 pc of the
Sun (Kryukova et al. 2012; Dunham et al. 2013, 2015).
In protostars, dust in the disk and envelope reprocesses the
shorter-wavelength radiation emitted by the central protostar
and the accretion shock on the stellar surface and reemits it
prominently at mid- to far-infrared wavelengths. As a result,
the combined emission of most protostellar systems (consisting
of protostar, disk, and envelope) peaks in the far-IR. Young,
The Astrophysical Journal Supplement Series, 224:5 (45pp), 2016 May doi:10.3847/0067-0049/224/1/5
© 2016. The American Astronomical Society. All rights reserved.
14
NASA Postdoctoral Program Fellow.
15
Hubble Fellow.
16
Current address: Leiden Observatory, Leiden University, P.O. Box 9513,
2300-RA Leiden, The Netherlands.
1
deeply embedded protostars have spectral energy distributions
(SEDs) with steeply rising slopes in the infrared, peaking
around 100 μm, and large fractional submillimeter luminosities
(e.g., Enoch et al. 2009; Stutz et al. 2013). Near 10 and 18 μm,
absorption by sub-micron-sized silicate grains causes broad
absorption features; in addition, there are several ice absorption
features across the infrared spectral range (Boogert et al. 2008;
Pontoppidan et al. 2008). These absorption features are
indicative of the amount of material along the line of sight,
with the deepest features found for the most embedded objects.
In addition, owingto the asymmetric radiation field, the
orientation of a protostellar system to the line of sight, whether
through a dense disk or a low-density cavity, plays a role in the
appearance of the SED. It influences the near- to far-IR slope,
the depth of the silicate feature, the emission peak, and the
fraction of light emitted at the longest wavelengths (see, e.g.,
Whitney et al. 2003b).
To classify young stellar objects (YSOs) into observational
classes, the near- to mid-infrared spectral index n (λF
λ
∝λ
n
)
from about 2 to 20 μm has traditionally been used (Adams et al.
1987; Lada 1987; André & Montmerle 1994; Evans et al. 2009;
Dunham et al. 2014). This index is positive for a Class 0/I
protostar, between −0.3 and 0.3 for a flat-spectrum source, and
between −1.6 and −0.3 for a Class II pre-main-sequence star.
Class 0 protostars are distinguished from Class I protostars as
having L
submm
/L
bol
ratios larger than 0.5%, according to the
original definition by André et al. (1993). Other values for this
threshold that have recently been used are 1% (Sadavoy
et al. 2014) and even 3% (Maury et al. 2011). Another measure
for the evolution of a young star is the bolometric temperature
(T
bol
), which is the temperature of a blackbody with the same
flux-weighted mean frequency as the observed SED (Myers &
Ladd 1993). A Class 0 protostar has T
bol
<70 K, a Class I
protostar 70 K<T
bol
<650 K, and a Class II pre-main-
sequence star 650 K<T
bol
<2800 K (Chen et al. 1995).
These observational classes are inferred to reflect evolutionary
stages, with the inclination angle to the line of sight being the
major source of uncertainty in translating classes to “stages”
(Robitaille et al. 2006; Evans et al. 2009). Also the accretion
history, which likely includes episodic accretion events and
thus temporary increases in luminosity, adds to this uncertainty
(Dunham et al. 2010; Dunham & Vorobyov 2012). Protostars
with infalling envelopes of gas and dust correspond to Stages 0
and I, with the transition from Stage 0 to I occurring when the
stellar mass becomes larger than the envelope mass (Dunham
et al. 2014). Young stars that have dispersed their envelopes
and are surrounded by circumstellar disks correspond to
Stage II.
By modeling the SEDs of protostars, properties of their
envelopes, and to some extent of their disks, can be
constrained. The near-IR is particularly sensitive to extinction
and thus constrains the inclination angle and cavity opening
angle, as well as the envelope density. Mid-IR spectroscopy
reveals the detailed emission around the silicate absorption
feature and thus provides additional constraints forboth disk
and envelope properties (see, e.g., Furlan et al. 2008). At longer
wavelengths, envelope emission starts to dominate. Thus,
photometry in the far-IR is necessary to determine the peak of
the SED and constrain the total luminosity and envelope
properties.
Here we present 1.2–870 μm SEDs and radiative transfer
model fits of 330 YSOs, most of them protostars, in the Orion
star formation complex. This is the largest sample of protostars
studied in a single, nearby star-forming region (distance of
420 pc; Menten et al. 2007; Kim et al. 2008) and therefore
significant for advancing our understanding of protostellar
structure and evolution. These protostars were identified in
Spitzer Space Telescope ( Werner et al. 2004) data by Megeath
et al. (2012) and were observed at 70 and 160 μm with the
Photodetector Array Camera and Spectrometer (PACS;
Poglitsch et al. 2010
) on the Herschel Space Observatory
17
(Pilbratt et al. 2010) as part of the Herschel Orion Protostar
Survey (HOPS),aHerschel open-time key program (e.g.,
Fischer et al. 2010; Stanke et al. 2010; Manoj et al. 2013; Stutz
et al. 2013; B. Ali et al. 2016, in preparation; W. J. Fischer
et al. 2016, in preparation). To extend the SEDs into the
submillimeter, most of the YSOs were also observed in the
continuum at 350 and 870 μm with the Atacama Pathfinder
Experiment (APEX) telescope (Stutz et al. 2013). Our sample
also includes 16 new protostars identified in PACS data
obtained by the HOPS program (Stutz et al. 2013; Tobin
et al. 2015; see Section 2). We use a grid of 30,400 protostellar
model SEDs to find the best fit to the SED for each object and
constrain its protostellar properties. As mentioned above, the
far-infrared data add crucial constraints for the model fits, given
that for most protostars the SED peaks in this wavelength
region, and therefore, within the framework of the model grid,
our SED fits yield the most reliable protostellar parameters to
date for these sources.
2. SAMPLE DESCRIPTION
The 488 protostars identified in Spitzer data by Megeath
et al. (2012) represent the basis for the HOPS sample
18
(see
Fischer et al. 2013; Manoj et al. 2013; Stutz et al. 2013). They
have 3.6–24 μm spectral indices −0.3 and thus encompass
flat-spectrum sources. To be included in the target list for the
PACS observations, the predicted flux of a protostar in the
70 μm PACS band had to be at least 42 mJy as extrapolated
from the Spitzer SED. Since targets were required to have a
24 μm detection, protostars in the Orion Nebula—where the
Spitzer 24 μm are saturated—are excluded. In addition, after
the PACS data were obtained, several new point sources that
were very faint or undetected in the Spitzer bands were
discovered in the Herschel data (Stutz et al. 2013). Fifteen of
them were found to be reliable new protostars. One more
protostar, which was not included in the sample of Stutz et al.
(2013) owingto its more spatially extended appearance at
70 μm, was recently confirmed by Tobin et al. (2015). We have
added these 16 protostars to the HOPS sample for this work
(see Appendix C). Most of these new protostars have very red
colors and are thus potentially the youngest protostars
identified in Orion (see Stutz et al. 2013).
Each object in the target list was assigned a “HOPS”
identification number, resulting in 410 objects with such
numbers; HOPS 394 to 408 are the new protostars identified by
Stutz et al. (2013), and HOPS 409 is the new protostar from
Tobin et al. (2015). Four of the 410 HOPS targets turned out to
17
Herschel is an ESA space observatory with science instruments provided by
European-led Principal Investigator consortia and with important participation
from NASA.
18
The selection of HOPS targets is based on an earlier version of the Spitzer
Orion Survey, and in addition some objects likely in transition between Stages I
and II were included; thus, not all protostars in the HOPS sample are classified
as protostars with envelopes in Megeath et al. (2012).
2
The Astrophysical Journal Supplement Series, 224:5 (45pp), 2016 May Furlan et al.
be duplicates, and 31 are likely extragalactic contaminants (see
Appendix C.2.2 for details). Some objects in the HOPS target
list were not observed by PACS; of these 33 objects, 16 are
likely contaminants, while the remaining objects were
originally proposedbut were not observed since they were
too faint to have been detected with PACS in the awarded
observing time. In addition, 35 HOPS targets were not detected
at 70 μm (see Appendices C.2.1 and C.2.2); eight of these are
considered extragalactic contaminants, while two of them
(HOPS 349 and 381) have only two measured flux values each,
making their nature more uncertain. One more target, HOPS
350, also has just two measured flux values (at 24 and 70 μm)
and is therefore also excluded from the analysis of this paper.
Similarly, we excluded HOPS 352, since it was only tentatively
detected at 24 μm (it lies on the Airy ring of HOPS 84) and in
none of the other data sets.
To summarize, starting from the sample of 410 HOPS
targets, but excluding likely contaminants and objects not
observed or detected by PACS, there are 330 remaining objects
that have Spitzer and Herschel data and are considered
protostars (based on their Spitzer classification from Megeath
et al. 2012). They form the sample studied in this work. Their
SEDs are presented in the next section, and in later sections we
show and discuss the results of SED fits for these targets. Their
coordinates, SED properties, and classification, as well as their
best-fit model parameter values, are listed in Table 1. The 41
likely protostars that lack PACS data (either not observed or
not detected) are presented in Appendix C.2.1.
3. SPECTRAL ENERGY DISTRIBUTIONS
3.1. Data
In order to construct SEDs for our sample of 330 YSOs, we
combined our own observations with data from the literature
and existing catalogs. For the near-infrared photometry, we
used J, H, and K
s
data from the Two Micron All Sky Survey
(2MASS; Skrutskie et al. 2006). For the mid-infrared spectral
region, we used Spitzer data from Kryukova et al. ( 2012) and
Megeath et al. (2012): the Infrared Array Camera (IRAC; Fazio
et al. 2004) provided 3.6, 4.5, 5.8, and 8.0 μm photometry,
while the Multiband Imaging Photometer for Spitzer (MIPS;
Rieke et al. 2004) provided 24 μm photometry. In addition,
most of the YSOs in the HOPS sample were also observed with
the Infrared Spectrograph (IRS; Houck et al. 2004) on Spitzer
using the Short-Low (SL; 5.2–14 μm) and Long-Low (LL;
14–38 μm) modules, both with a spectral resolution of about 90
(see, e.g., Kim et al. [2016] for a description of IRS data
reduction). Herschel PACS data at 70, 100, and 160 μm
yielded far-infrared photometric data points (B. Ali et al. 2016,
in preparation; the 100 μm data are from the Gould Belt
Survey; e.g., André et al. 2010). Most YSOs were also
observed at 350 and 870 μm (see Stutz et al. 2013) by the
APEX telescope using the SABOCA and LABOCA instru-
ments (Siringo et al. 2009, 2010, respectively
). Thus, our SEDs
have well-sampled wavelength coverage from 1.2 to 870 μm;
we did not include additional data from the literature in order to
preserve a homogeneous data set for all the objects in our
sample.
The aperture radius used for the photometry varies
depending on the instrument and wave band. The photometry
in the 2MASS catalog was derived from point-spread function
(PSF) fits using data from 4″ apertures around each object (see
the Explanatory Supplement to the 2MASS All Sky Data
Release and Extended Mission Products). Megeath et al. (2012)
used an aperture radius of 2
4 for IRAC and PSF photometry
for MIPS 24 μm data. We used aperture radii of 9
6 and sky
annuli of 9
6–19 2 for PACS 70 and 100 μm images; we then
applied aperture correction factors of 0.7331 and 0.6944 to the
70 and 100 μm fluxes, respectively. For PACS 160 μm, we
used an aperture radius of 12
8, a sky annulus of 12 8–25 6,
and an aperture correction factor of 0.6602. In some cases
(background contamination, close companions) we used PSF
photometry at 70 and 160 μm instead (see B. Ali et al. 2016, in
preparation, for details). Finally, we adopted beam fluxes at
350 and 870 μm (with FWHMs of 7
34 and 19″, respectively).
The IRS SL module has a slit width of 3
6, while the LL
module is wider, with a slit width of 10
5. Sometimes the flux
level of the two segments did not match at 14 μm (owingto
slight mispointings or more extended emission from surround-
ing material measured in LL), and in these cases usually the SL
spectrum was scaled by at most a factor of ∼1.4 (typically
1.1–1.2). In a few cases, especially when the LL spectrum
included substantial amounts of extended emission or flux from
a nearby object, the LL spectrum was scaled down to match the
flux level of the SL spectrum at 14 μm, typically by a factor of
0.8–0.9. We discuss how the different aperture sizes are
accounted for in the model fluxes in Section 4.2.
The SEDs of our HOPS sample are shown in Figure 1
together with their best-fit models from our model grid (see
sections below); the data are listed in Table 2. Many objects
display a deep silicate absorption feature at 10 μm and ice
features in the 5–8 μm region, as expected for protostars. Those
objects with very deep 10 μm features and steeply rising SEDs
are likely deeply embedded protostars, often seen at high
inclination angles.
3.2. Multiplicity and Variability
A large fraction (203 out of 330) of the young stars in our
sample have at least one Spitzer-detected source within a radius
of 15″; in most cases, this “companion” is faint in the infrared
and likely a background star or galaxy. Thus, the emission at
far-IR and submillimeter wavelengths is expected to be
dominated by the protostar or pre-main-sequence star, and we
can assume that the SEDs are representative of the YSOs even
if the nearby sources cannot be separated at these wavelengths.
There are a few YSOs that have objects separated by just 1″–3″
and are only resolved in one or two IRAC bands (HOPS 22, 78,
108, 184, 203, 247, 293, 364); in these cases we used the
flux at the IRAC position that most closely matched those at
longer wavelengths. We note that some of these very close
“companions” are likely outfl
ow knots. There are also
unresolved binaries, which appear as single sources even in
the IRAC observations (Kounkel et al. 2016); in these cases our
SEDs show the combined flux in all wave bands. If two point
sources are not fully resolved and the resulting blended source
is elongated, no IRAC photometry was extracted. In such cases,
a protostar may not have IRAC fluxes even though it was
detected in the Spitzer images.
There are also several protostars that lie close to other
protostars: HOPS 66 and 370 (d = 14
9), HOPS 76 and 78
(d = 14
1), HOPS 86 and 87 (d = 12 1), HOPS 117 and 118
(d = 13
7), HOPS 121 and 123 (d = 7 6), HOPS 124 and 125
(d = 9
8), HOPS 165 and 203 (d = 13 3), HOPS 175 and 176
(d = 8
0), HOPS 181 and 182 (d = 10 2), HOPS 225 and 226
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The Astrophysical Journal Supplement Series, 224:5 (45pp), 2016 May Furlan et al.
Table 1
Classification and Best-fit Model Parameters for the HOPS Sample
Object R.A. Decl. Class L
bol
T
bol
n
4.5–24
L
tot
R
disk
ρ
1000
M
env
θ iA
V
Scaling R
(°)(°)(L
e
)(K)(L
e
)(au)(gcm
−3
)(M
e
)(°)(°)(mag) Factor
(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)
HOPS 1 88.5514 1.7099 I 1.517 72.6 1.469 3.0 100 2.38×10
−19
0.0133 5 63 23.2 0.99 2.319
HOPS 2 88.5380 1.7144 I 0.542 356.5 0.455 1.3 5 2.38×10
−20
0.0012 15 32 13.1 1.30 2.476
HOPS 3 88.7374 1.7156 flat 0.553 467.5 0.260 0.820 5 1.19×10
−20
0.0007 5 50 3.0 0.81 3.331
HOPS 4 88.7240 1.7861 I 0.422 203.3 1.243 0.600 5 1.78×10
−19
0.0099 5 63 2.5 2.00 4.139
HOPS 5 88.6340 1.8020 I 0.390 187.1 0.626 1.6 50 2.38×10
−19
0.0096 35 63 12.4 0.52 2.459
HOPS 6 88.5767 1.8176 I 0.055 112.5 1.308 0.210 5 1.78×10
−20
0.0010 5 76 8.0 2.00 4.091
HOPS 7 88.5835 1.8452 0 0.528 58.0 1.707 6.1 100 1.78×10
−20
0.0010 15 81 18.7 2.00 2.981
HOPS 10 83.7875 −5.9743 0 3.330 46.2 0.787 5.4 500 2.38×10
−18
0.135 5 70 0.0 1.77 3.168
HOPS 11 83.8059 −5.9661 0 8.997 48.8 2.200 33.2 100 2.38×10
−18
0.115 25 63 39.8 1.10 3.385
HOPS 12 83.7858 −5.9317 0 7.309 42.0 1.815 5.8 100 5.94×10
−18
0.332 5 32 0.0 1.91 2.207
HOPS 13 83.8523 −5.9260 flat 1.146 383.6 0.208 2.4 5 5.94×10
−20
0.0031 15 18 15.2 0.78 2.149
HOPS 15 84.0792 −5.9237 flat 0.171 342.0 0.116 0.600 50 2.38×10
−18
0.0745 45 63 9.0 2.00 3.329
HOPS 16 83.7534 −5.9238 flat 0.682 361.0 0.019 3.0 5 1.78×10
−18
0.0548 45 18 25.4 0.99 2.464
HOPS 17 83.7799 −5.8683 I 0.299 341.3 0.389 1.5 500 1.78×10
−19
0.0080 35 63 0.0 0.50 5.279
HOPS 18 83.7729 −5.8651 I 1.419 71.8 0.743 5.2 50 1.78×10
−18
0.0851 25 76 1.1 0.51 4.915
HOPS 19 83.8583 −5.8563 flat 0.188 101.6 −0.098 0.150 500 1.19 ×10
−16
6.53 15 18 3.7 0.50 5.445
HOPS 20 83.3780 −5.8447 I 1.231 94.8 2.226 1.6 5 5.94×10
−19
0.0329 5 76 7.3 0.54 5.333
HOPS 22 83.7522 −5.8172 II 0.100 238.2 0.494 0.290 5 1.19×10
−20
0.0007 5 63 7.5 0.97 3.049
HOPS 24 83.6956 −5.7475 I 0.095 288.9 0.438 0.150 50 1.78×10
−19
0.0099 5 57 3.2 0.50 3.998
HOPS 26 83.8223 −5.7040 II 0.484 1124.9 −0.400 1.1 5 1.78×10
−20
0.0007 35 70 0.0 1.10 3.291
HOPS 28 83.6971 −5.6989 0 0.494 46.3 1.342 2.6 100 1.78×10
−18
0.0731 35 76 2.4 0.84 3.327
HOPS 29 83.7044 −5.6950 I 1.916 148.2 0.687 6.1 500 1.19×10
−19
0.0044 45 63 3.8 0.60 4.113
HOPS 30 83.6836 −5.6905 I 3.791 81.2 1.836 21.2 100 1.19×10
−17
0.381 45 57 39.5 0.70 2.494
HOPS 32 83.6477 −5.6664 0 2.011 58.9 0.937 3.0 5 1.78×10
−18
0.0937 15 70 7.7 0.97 3.527
HOPS 33 83.6884 −5.6658 flat 0.120 777.6 −0.397 0.400 5 1.78 × 10
−19
0.0071 35 70 5.3 1.34 3.797
HOPS 36 83.6101 −5.6279 flat 1.024 374.6 0.005 2.2 5 5.94×10
−20
0.0031 15 18 16.4 0.71 3.552
HOPS 38 83.7697 −5.6201 0 0.246 58.5 0.935 2.0 5 1.78×10
−16
5.48 45 18 80.0 1.96 7.198
HOPS 40 83.7855 −5.5998 0 2.694 38.1 1.247 6.1 100 2.38×10
−17
0.974 35 41 82.6 2.00 5.459
Note. Column (1) lists the HOPS name of the object, columns (2) and (3) its J2000 coordinates in degrees, column (4) the type based on SED classification, column (5) the bolometric luminosity, column (6) the
bolometric temperature, column (7) the 4.5–24 μm SED slope, and columns (8)–(16) the best-fit model parameters: the total luminosity, the disk radius (which is equal to the centrifugal radius), the reference density at
1000 auρ
1000
, the mass of the envelope within 2500 au, the cavity opening angle, the inclination angle, the foreground extinction, the scaling factor applied to the best-fitting model from the grid, and the R value.
(This table is available in its entirety in machine-readable form.)
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The Astrophysical Journal Supplement Series, 224:5 (45pp), 2016 May Furlan et al.
Figure 1. SEDs of the HOPS targets modeled in this work (black; open symbols: photometry, arrows: upper limits, line: IRS spectrum). The best-fit model for each
object is shown as a red line, with fluxes taken from a 4″ aperture for λ<8 μm, a 5″ aperture for λ =8 –37 μm, and a 10″ aperture for λ>37 μm. The red symbols
are the model photometry measured in the same apertures and bandpasses as the data (see Section 4.2 for details). Only the first 15 SEDs are shown here.
(The complete figure set ( 22 images) is available online.)
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The Astrophysical Journal Supplement Series, 224:5 (45pp), 2016 May Furlan et al.
