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A Novel Survey for Young Substellar Objects with the W band Filter.V. IC 348 and Barnard 5 in the Perseus Cloud

We report the discovery of substellar objects in the young star cluster IC 348 and the neighboring Barnard 5 dark cloud, both at the eastern end of the Perseus star-forming complex. The substellar candidates are selected using narrowband imaging, i.e., on and off photometric technique with a filter centered around the water absorption feature at 1.45 microns, a technique proven to be efficient in detecting water-bearing substellar objects. Our spectroscopic observations confirm three brown dwarfs in IC 348. In addition, the source WBIS 03492858+3258064, reported in this work, is the first confirmed brown dwarf discovered toward Barnard 5. Together with the young stellar population selected via near- and mid-infrared colors using the Two Micron All Sky Survey and the Wide-field Infrared Survey Explorer, we diagnose the relation between stellar versus substellar objects with the associated molecular clouds. Analyzed by Gaia EDR3 parallaxes and kinematics of the cloud members across the Perseus region, we propose the star formation scenario of the complex under influence of the nearby OB association.


INTRODUCTION
Stars are formed in groups out of dense molecular fragments, whereas planets are condensed in young circumstellar disks. Brown dwarfs (mass 0.07 M , Dupuy & Liu 2017) and planet-mass objects (mass 0.013 M ), collectively called substellar objects, are not massive enough to sustain core hydrogen fusion, and therefore cool and fade after birth, even though massive brown dwarfs are expected to undertake core fusion by shortsupplied deuterium and lithium, or even by protons before the core becomes degenerate (e.g., Rebolo et al. apparent magnitude of m J ∼ 18 mag at 200 pc given a moderate extinction A J = 1 mag. A reliable catalogue of substellar members is the first crucial step to supplement the stellar population within the same cloud, i.e., to derive the mass function, and to test theories of stellar versus substellar formation. At the lowest-mass end, the free-floating planets serve as a comparison sample to exoplanets, as to the similarities and differences in formation and evolution (Lucas & Roche 2000); e.g., to test the progression of cloud fragmentation to very low masses or the existence of a population of ejected giant planets (Sumi et al. 2011).
Wide-field surveys have played a major role in recognition of substellar objects in the solar neighborhood, such as by Pan-STARRS (PS1; Chambers et al. 2016), the Wide-Field Infrared Explorer (WISE; Wright et al. 2010), the UKIRT Infrared Deep Sky Survey (UKIDSS; Lawrence et al. 2007), the Two Micron All Sky Survey (2MASS; Skrutskie et al. 2006), the DEep Near-Infrared Survey of the Southern sky (DENIS; Epchtein et al. 1994), the Sloan Digital Sky Survey (SDSS; Blanton et al. 2017), the VISTA Hemisphere Survey (VHS; McMahon et al. 2019), etc. Interstellar dust extinction makes it difficult in optical and near-infrared wavelengths to distinguish between background giant stars and equally faint substellar objects. The largest limiting factor for these surveys is the need for spectroscopic confirmation of photometrically selected candidates, which is very time-consuming unless a highly reliable candidate list is available. Supplementing the usual broadband photometry to diagnose cool atmospheres, we use a custom IR filter (with a bandpass width 6%) centered around 1.45 µm to detect the flux suppression due to H 2 O absorption commonly seen in the spectra of low-mass stars, brown dwarfs, and planetary-mass objects (Allers & Liu 2020). The combination of the water band (referred to as the W -band) photometry along with J and H magnitudes proves effective in distinguishing young substellar objects from reddened background stars that lack water absorption in their atmospheres (Jose et al. 2020;Dubber et al. 2021).
The Perseus molecular cloud complex, located to the west of the Per OB2 association, is active in star formation, with a few distinct subregions including two young populous star clusters, IC 348 and NGC 1333, and dark clouds such as L1468, L1448, L1451, L1455, Barnard 1, and Barnard 5 (B5, also known as L1471; Jørgensen et al. (2006); Rebull et al. (2007). Here we report identification of substellar objects in IC 348 and in B5, both to the eastern end of the complex. This list, together with the young stellar counterparts, provides two con-trasting samples, a crowded (IC 348) versus a relatively isolated (B5) environment.
IC 348 (α = 03 h 44 m 30 s .78, δ = +32 • 10 19 .0, J2000) harbors nearly 500 known members (Luhman et al. 2016) with the most massive being a B5 star (HD 281159). Distance determinations to the cluster range from 321 ± 10 pc by Ortiz-León et al. (2018) using VLBA, 320 ± 26 pc by Gaia Collaboration et al. (2016Collaboration et al. ( , 2018, to 295 ± 15 pc by Zucker et al. (2018). The age of the cluster has been estimated to be 2-3 Myr (Luhman et al. 2003). However, the young population seems to have a lower disk fraction given its age (Cieza et al. 2015). Indeed, Ruíz-Rodríguez et al. (2018) using ALMA detected typical disk masses in the Class II objects in IC 348 to be lower than in Taurus, Chamaeleon, or σ Ori, all with ages 1-5 Myr, thus indicating an older age (6 Myr) for IC 348 (Bell et al. 2013;Cottaar et al. 2014). In a separate site ∼ 10 to the southwest of the star cluster, ongoing star formation (1-2 Myr) is witnessed to be spatially coincident with dense clouds, protostars, and Herbig-Haro objects, suggestive of noncoeval episodes of star birth in the region (Tafalla et al. 2006).
Farther to the northeast of IC 348 (∼ 3 pc), at the far end of the cloud complex, is B5, an isolated globule with cold (Beichman et al. 1984) and large dust grains (Bhatt 1986). More distant than IC 348 (350 pc; Herbig & Jones 1983;Langer et al. 1989), and spanning some 45 in the sky, B5 is relative massive (∼ 10 3 M , Goldsmith et al. (1986); Langer et al. (1989)) and known also to have ongoing star formation, yet hosting several dense cores (Fuller et al. 1991;Olmi et al. 2005;Hatchell et al. 2005;Kirk et al. 2006), fragmenting cloud filaments (Piñeda et al. 2015), and Herbig-Haro objects (Walawender et al. 2005). An overall low star formation efficiency is in vast contrast to the adjacent IC 348 cluster which is prolific in star birth (Hatchell et al. 2007).
This paper is a continuation of the W-band series on substellar objects using the novel W -band technique in nearby star-forming regions (Allers & Liu (2020); Jose et al. (2020);Dubber et al. (2021), Dubber et al. (2022) submitted). We report here deep imaging surveys using the W -band, combined with J and H bands, to identify young brown dwarfs in IC 348 and B5. While the young stellar population in IC 348 is relatively well known, our focus in this cloud is on newly found brown dwarfs. For B5, on the other hand, in addition to the substellar candidates found with the W -band imaging, we have conducted a census of young stars with nearand mid-infrared colors. Finally we have characterized the distance and kinematics of the young objects found in IC 348 and in B5, and will discuss them in the con-text of the overall morphology and motion of the whole Perseus cloud complex as evidence of the star formation history therein.

OBSERVATION AND DATA ANALYSIS
The data used in this study include the water-band images to select substellar candidates, plus archival near-and mid-infrared photometry from 2MASS and WISE to identify young stars with dusty circumstellar disks, and Gaia EDR3 for parallax and kinematics.

CFHT/WIRCam Water-Band Imaging
IC 348 was observed on March 18 th , 2016, July 16 th , 2016, and December 08 th , 2017; and B5 was observed on October 23 rd 2015 (all in UT), with the Canada-France-Hawaii Telescope (CFHT) using the Wide Field Infrared Camera (WIRCam; Puget et al. 2004). With a field of view of ∼ 20 × 20 and ∼ 0.306 pixels, we used a 21-point dithering pattern to fill the gaps between the four detectors of WIRCam and to subtract the sky background. Images were processed by the CFHT 'I'iwi pipeline. Darks exposure times were 10 sec in J-, and 65 sec for H-and W -bands. Normalized flat-field corrections for each filter was constructed after each observing run. Before stacking the images, saturated and bad-pixel were flagged, non-linearity were corrected, and images were dark subtracted, flat-field corrected, skysubtracted, cross-talk removed and 1/f noise corrected by 'I'iwi. The total integration time for J, H, and W bands for IC 348 was 170, 210, and 1495 s, respectively, and for B5 it was 50 s (J), 75 s (H), and 455 s (W ), respectively.
To calibrate the J-band and H-band stacks, we adjusted the zero point by including a color term between 2MASS and the MKO system of WIRCam by clipping the magnitudes in the range 14.5 ≤ J ≤ 16 mag and 14.5 ≤ H ≤ 15.5 mag, with the lower limit being the saturation limit of the WIRCam, and the upper limit being decided by the errors of 2MASS magnitudes (i.e., < 0.1 mag). We used the color correction from Leggett et al. (2006) to convert the 2MASS J and H magnitudes to the MKO system, and then found the zero point offset for each of the J and H bands.
In absence of 2MASS equivalents, the zero point of the W -band photometry was determined with a different strategy. Following Allers & Liu (2020), we adopt a Q index as a measure of the flux suppression in the Wband relative to the dereddened continuum between Jand H-bands, as shown in Eq. 1, where J and H are the magnitudes already calibrated, W is the W -band magnitude to be calibrated, and e = (A J − A W )/(A W − A H ) is an empirical coefficient to account for the reddening across the bands. To calibrate the W magnitude, the median Q value, Q f , for the majority of bright stars most likely lacking water absorption is adjusted so that Q f ≈ 0; that is, which, based on our synthetic photometry for a field star (i.e., M0) yielding Q f = −0.043, and have adopted e = 1.61 (Allers & Liu 2020). The W -band zero point is then applied to offset the WIRCam instrumental magnitude. The calibrated J, H, and W magnitudes together allow the Q index to be used to quantify the flux suppression in the W band to select water-bearing candidates, with the methodology to be detailed later in Sec. 3.1

Spectroscopic Observations
Spectroscopic follow-up observations were conducted with the SpeX spectrograph on the IRTF (Rayner et al. 2003). The targets were chosen as being sufficiently bright (H < 17 mag), and were checked whether they were already known brown dwarfs (Muench et al. 2007;Luhman et al. 2016;Alves de Oliveira et al. 2013). We incorporated available information from SIMBAD, 2MASS, PanSTARRS, and UKIDSS photometry. In order to select targets for spectroscopic follow-up with no photometric peculiarity.
Three targets in IC 348 were observed on February 18 th , 2017, and one target on January 12 th , 2022 (all in UT). A standard ABBA nodding pattern was utilized to obtain the sky and target data, with a total integration time of 1473 s for each target. The observation were taken in the prism mode using a 0.8 slit, which corresponds to an average resolving power of R ∼ 100. Flat field frames and wavelength calibration using an argon lamp were taken before or after a set of observations. We used SPEXTOOL (V4.1 Cushing et al. 2005), an IDL-based data reduction package, to extract the spectra. An A0 standard star, either HD 25152 or HD 23512, was observed either before or after a science target for telluric corrections. The IRTF spectra for IC 348 are shown in Fig. 2.
Three B5 targets were observed on January 12 th , 2022 (UT), also in the prism mode, but with a 0.5 slit and with the standard star HD 22859, following the same data reduction procedure. The spectra of the three B5 targets are shown in Fig. 3  The census of the young stellar population in IC 348 has been relatively comprehensive in the literature, therefore our attention was mainly on the substellar objects, but for B5, we pay attention to the stellar as well as substellar objects in general. We conducted a search within a field of ∼ 30 toward B5 for young stellar candidates using near-and mid-infrared colors, with   2MASS (Cutri et al. 2003) photometry in J (1.25 µm), H (1.65 µm), and K s (2.15 µm) bands, and WISE (Cutri et al. 2012) in W 1 (3.4 µm), W 2 (4.6 µm), W 3 (12 µm), and W 4 (22 µm) bands. There are 10588 WISE sources within the B5 field, of which 1140 have photometric quality flag 'AAA' (206) or 'AAB' (934), i.e., with an uncertainty less than 0.1 mag (for A) or 0.3 mag (for B) in respective bands, whereas among the 4282 2MASS sources, 1985 have photometric quality flag 'AAA' with uncertainty 0.1 mag.

Gaia EDR3
We made use of the Gaia Early Data Release 3 (Gaia EDR3) (Gaia Collaboration et al. 2021) which provides homogeneous astrometry (coordinates, trigonometric parallax, and proper-motion) of about 1.5 billion sources of the entire sky. Broad-band photometry in G, G BP , and G RP with passbands of 330-1050 nm, 330-680 nm, and 630-1050 nm respectively are also available. We analyzed the Gaia EDR3 data towards IC 348, and B5, plus three other regions in the Perseus complex to diagnose the parallax and kinematic properties.

Selection of Brown Dwarf Candidates
The use of the Q index to distinguish brown dwarfs from reddened background objects (see Allers & Liu 2020;Jose et al. 2020;Dubber et al. 2021, for detailed descriptions) is much more effective than using broadband photometric colors alone. With the definition of Q in Eq. 1, and the ratio of extinction in the three bands, which depends on the adopted reddening law. To set this value, we calculated synthetic photometry for an M0 spectra taken from Kirkpatrick et al. (2010), reddened by A V = 10 mag and R V = 3.1 reddening law of Fitzpatrick (1999). Next, we compared the reddened and unreddened synthetic photometry of the M0 spectra and adopted extinction coefficient to be e = 1.61 (see Allers & Liu (2020)). A typical contaminant star would have Q ∼ 0 (without water absorption), whereas for a later-type object the Q-index would be negative due to water absorption, as presented in Figure 4 for IC 348. By using the synthetic photometry in J, H, and W of young objects (Muench et al. 2007;Allers & Liu 2013) and field dwarfs (Cushing et al. 2005), we concluded that objects with spectral types later than M6 would have Q < −0.6. Including the uncertainty σ Q , estimated by calculating the errors in quadrature, namely, we therefore considered sources with Q ≤ −(0.6 + σ Q ) for plausible presence of water absorption, i.e., as substellar candidates, and with H > 14 mag to avoid photometric saturation. The limitation to our approach is that, if a young substellar object is still embedded in the parental material and/or have a substantial mass accretion, thereby entailing strong veiling (Luhman & Rieke 1999), our technique may not be able to identify it. In addition to molecular features, criteria of cool atmospheres can be added (e.g., Chiang et al. 2015). For this we imposed the condition (W 1−W 2) > 0.10, the intrinsic color for a spectral type later than M6 (Kirkpatrick et al. 2011). We also cross-matched with Pan-STARRS 1 (Chambers et al. 2016) to remove objects with bright optical counterparts, i.e., (z P S1 − J CF HT ) ≤ 2 (Knapp et al. 2004). Because of the large WISE pixel scale, we inspected visually are the Pan-STARRS 1 and CFHT images for each candidate to ensure the (W 1−W 2) color not to be affected by blends with other sources. Combining both the water absorption and cool temperature criteria i.e., (W 1 − W 2)> 0.10 and (z P S1 − J CF HT )≤ 2, and by excluding any known members found in literature (i.e., Muench et al. (2007) In Figure 5 we demonstrate that an increasingly negative value of Q corresponds to an object with a later type.
Here we show Q versus spectral type (SpT) of all the known members in the literature and spectroscopically identified substellar objects in IC 348.  . New discoveries from this work (confirmed spectroscopically) i.e., substellar objects are shown in red with respective error bars. The orange dashed line denotes Q = −0.6, below which the Q value indicates a spectral type later than M6, corresponding to a substellar boundary for young objects.   Figure. 4 but for Barnard 5 (here with 2089 sources in gray). The black symbols mark those satisfying criteria of Q ≤ −(0.6 + σQ) and H > 13.5 mag (23 targets). The red symbols mark candidates that have been followed up spectroscopically with IRTF/SpeX, and the blue symbols show candidates too faint to be observed with IRTF/SpeX. Note that both the red and blue symbol targets satisfy the water absorption and cool temperature criteria i.e., (W 1 − W 2)> 0.10 and (zP S1 − JCF HT )≤ 2.

Spectral Fitting
We compared our spectra with library templates for spectral typing. Those for field brown dwarfs are taken from the SpeX library (Cushing et al. 2005;Rayner et al. 2009) whereas spectra for young brown dwarfs are adopted from Luhman et al. (2017). Each standard star belongs to one of the three age groups: VL-G (very low gravity ≈ 1 Myr), INT-G (intermediate gravity, with two subgroups: I for 10 Myr and Y for 5 Myr), or FLD-G (gravity for much older field stars). The data are dereddened by A V ranging from 0 to 40 mag, using the reddening law from Fitzpatrick (1999). For further details on spectral classification, please see Dubber et al. (2021).
Spectra of young objects later than M5 show a characteristic inverted "V" (triangular) shape in the H band (Cushing et al. 2005). This feature, where H band is dominated by the strong water absorption bands peaking around 1.70 µm, was first reported by Lucas et al. (2001) seen in young cool objects. The triangular peak in the H-band is attributed to the effect of lowpressure and low-gravity atmospheres (Lucas & Roche 2000;Allers & Liu 2013;Allers et al. 2007). We found three new substellar objects in IC 348 with spectral type ≥M5 placing them at the boundary of the substellar regime (see Figure 7(a), (b) and (c)).
In B5, the source 03481542+3309185 has a spectral type of M4±0.5 and can be fitted by either a field or a young template and finally assigned the object as a field dwarf. Spectral classification according to Zhang et al. (2018) this object has a spectral type of M5.2±0.9 and a low surface gravity object (VL-G). This source therefore could either be a field or a young substellar object. The source 03492858+3258064, is the first confirmed brown dwarf toward B5 (see Figure 7(d)). Three targets were too faint to be observed with IRTF/SpeX, so we refer as brown dwarf candidates (see Table 2). The newly identified substellar objects in IC 348 and in B5 are summarized in Table 1. Column 1 gives the ID in the water-band survey, followed by columns 2 and 3 of the coordinates. In Columns 4 and 5 we list the J, and H band magnitudes measured by the CFHT/WIRCam. Column 6 gives the WISE W 1 and W 2-bands. Column 7 gives the difference between z-band in PanSTARRS and J CFHT . The W band data along with J, and H band magnitudes, lead to the derived Q parameter in Column 8 (see Eq. 1), used to identify brown dwarf candidates. Columns 9, 10 gives the spectral type and A V obtained from spectral fitting. In Column 11 the Age estimation is based on the spectral fitting mentioned above. The bolometric correction needed to calculate L bol in Columns 12 and T eff in Column 13 are taken from Filippazzo et al. (2015) (for spectral type M7 or later) or Herczeg & Hillenbrand (2014) (earlier than M7), depending upon the spectral type of the object.    Notea The uncertainty in the spectral classification type is 0.5 subtype.
b The age is estimated based on spectral fitting in Dubber et al. (2021) (please see Figure 7). † This target does not have a counterpart in the Pan-STARRS (PS1) catalog. The PS1 images were visually inspected. The target is not visible in g,r, or i band, and is faint in z and y bands.  BDc · · · · · · · · · Note-The uncertainty in the spectral classification type is 0.5 subtype. BDc refers to brown dwarf candidate.

Physical Properties
We infer the range of age and mass of each confirmed substellar object with the evolutionary tracks from Baraffe et al. (2015). The bolometric magnitudes and the effective temperatures (T eff ) for our targets were determined using the technique described in Section 6.4 of Dubber et al. (2021). In a nutshell we used the CFHT photometry and created a grid of SpT-A V probability maps to calculate the bolometric magnitude and luminosity. Each point in the grid has a χ 2 value associated, which we convert into a normalized probability. Monte Carlo analysis was performed, using 500,000 model objects and distribute proportionally across the SpT-A V grid using the probability for each bin. For each simulated object of each SpT-A V probability bin, we calculated the bolometric magnitude (using Eq 4 in Dubber et al. (2021)) by sampling Gaussian distributions of distance modulus, d mod and apparent magnitude m J . The Gaussian distribution of m J is created using the CFHT apparent magnitude and error.
We adopt the bolometric correction, BC J for a spectral type earlier than M7 (Herczeg & Hillenbrand 2015), or for an M7 or later (Filippazzo et al. 2015). We obtain bolometric luminosity (L bol /L ) using Eq 5 in Dubber et al. (2021) by converting the bolometric magnitude to bolometric luminosity. We convert this grid of (L bol /L ) into histogram distributions, and find the peak with errors derived from 68% Bayesian credible interval. The effective temperature (T eff ) plotted here is estimated using the derived spectral type and relations given in Table 5  As a separate analysis, we constructed the colormagnitude diagram for each region, and compared the AMES-Cond and AMES-DUSTY models  to estimate the age of the substellar objects. This is displayed in Figure 9. In IC 348, two out of three brown dwarfs are consistent with an age of ∼ 5 Myr, regardless of the Cond or the Dusty model. Here the isochrones are adjusted by a distance modulus of 7.46 mag and an extinction/reddening of E(B − V ) = 0.71 mag (Trullols & Jordi 1997). In B5, the distance modulus of 7.72 mag is adopted, but the extinction to the cloud is unclear so three different values of E(B −V ) are exercised, at 0, 0.5, and 1.0 mag. The single brown dwarf in B5 seems to fit well with an age of 5 Myr and a mild extinction of E(B − V ) = 0.5 mag.
The age of IC 348 has been estimated in the literature to be 1-6 Myr (Bell et al. 2013;Cottaar et al. 2014;Luhman et al. 2003) and the three newly identified substellar objects indeed follow approximately the age range; it is assuring also that all the targets have masses close to the stellar/substellar boundary, i.e., 0.1 M .
The source 03435016+3204073 in IC 348 lies above the 0.5 Myr isochrone in Figure 8, therefore we cannot determine its mass or age reliably. A possible reason might be it being a reddened very low-mass star or a brown dwarf binary. The same source appears also highly reddened in Figure 9. It is interesting that its J − H versus J location resembles that of a blackbody (Burrows et al. 1997). The nature of this object deserves further delineation.
In B5, the newly identified brown dwarf has an isochrone age of ∼ 5 Myr and a mass of 0.05 M . This is the first discovery of a brown dwarf to date toward B5 to our knowledge. The age group assigned to this confirmed brown dwarf is INT-G (≈ 10 Myr) which may imply that this object is likely to be a young interloper, possibly slightly closer to us than B5. Studies of such a widely distributed young low-mass objects from previous generation of newly formed stars is seen in Orion cloud complex, and is possible to see such a distribution in Perseus complex.

Selection of Young Stellar Members In B5 Using WISE and 2MASS
We adopted the scheme given by Koenig & Leisawitz (2014), i.e., with color cuts from W 1 to W 3 for different YSO classes, and removing possible contaminants such as active galactic nuclei, and star-forming galaxies. Using the (W 1 − W 2) versus (W 2 − W 3) diagram, we identified five Class I and 11 Class II candidates, as shown in Fig. 10(a).
There are 1985 2MASS sources with quality flag 'AAA'. Of the YSO candidates found by the WISE colors, Nos. 7, 16 (both Class I) and No. 10 (Class II) in Table 3 have no 2MASS counterparts, whereas three out of five Class I, and 10 out of 11 Class II sources have reliable 2MASS measurements, allowing us to conduct consistency check of their youth nature, depicted in Fig. 10(b). Two of the Class II candidates, Nos. 2 and 13 in Table 3, have consistent 2MASS colors with being T Tauri stars, whereas the rest lie along the giant loci. No. 11 as a Class II candidate has a counterpart in our CFHT images and was selected as a Q candidate for a follow-up spectroscopy. This target 03492858+3258064 turns out to be the first confirmed brown dwarf in B5.

Kinematics of IC 348 and B5
The proper-motion vector plot of IC 348 displayed in Figure 11 6.51 mas yr −1 , and µ δ = −9.99 mas yr −1 . The two kinematic groups are also distinguished in parallax and in sky position (Figure 11(b) and 11(c)). Group A is bimodal in the parallax distribution, as illustrated in Figure 11(b), peaking near 0.5 mas, coincident with the field distribution, and another more populous that peaks at 3.1 mas. Group B contains less stars, but exhibits also two maxima at about the same parallax values as above. The positional distribution clarifies the origin of each kinematic group; namely, Group A is by and large centrally concentrated, i.e., the cluster of IC 348 itself, whereas stars in Group B are dispersed throughout the field. The reciprocal of the mean parallax of Group A (3.1 mas), 323 pc is consistent with the distance to IC 348 (Ortiz-León et al. 2018), confirming that Group A is the cluster, whereas a fraction of Group B, the ones at similar distances, is the general young stellar population permeating the Perseus complex. For B5, adopting the coordinates given by Pezzuto et al. (2021), we see no well-defined grouping in proper-motion in Figure 12(a), unlike that in IC 348. We crossmatched the list of young stellar population known in the literature (i.e., Simbad) with Gaia EDR3 sources (Gaia Collaboration et al. 2021), within a coincidence radius of 5 resulting in 12 objects classified as "YSO", or a candidate "YSO". In the parallax distribution of the young stellar objects, there is a peak within a narrow range between 2.0 mas to 2.6 mas, (see Figure. 12(b)). We have listed only those YSOs that are within the given parallax range in Table. 4. The mean parallax, and proper-motion are, 2.35 mas, µ α = 4.00 mas yr −1 , µ δ = −5.32 mas yr −1 (see Table 5) respectively. The reciprocal of the mean parallax corresponds to a distance of 426 pc therefore placing it farther away than what suggested by Herbig & Jones (1983) or Dickman (1978) as 350 pc.  We look for additional evidence of youth by using the WISE and 2MASS colors. A total of 16 young stellar objects are found, of which one Class I object and seven Class II objects are newly found. They are listed in Table 3, in which a sequence number, the coordinates, WISE and 2MASS magnitudes, are given, followed by the name known in the literature, if any, and the classification of the object.   Note-* These sources have Gaia counterparts either with no propermotion data or with a large error. † Source No. 14 and Source No. 15 are slightly outside our Gaia field, but both are within our proper-motion criterion. Beichman et al. (1984) reported four IRAS sources in the vicinity of B5, among which IRS 1 (IRAS 03445 + 3242) is the youngest and the first embedded YSO. Located near the center of the cloud, the source (No. 1 in Table 3) is very cold, temperature and luminosity being 30-100 K, 10 L respectively, Beichman et al. (1984) and are associated with CO outflows (Zapata et al. 2014), bow-shocks, Herbig-Haro objects (HH 366E and HH 366W, Yu et al. 1999;Bally et al. 1996), and shock-excited H 2 emissions. IRS 1 has a circumstellar disk whose orientation is perpendicular to the CO outflow (Langer et al. 1996;Fuller et al. 1991), and also exhibits a highly collimated optical jet (Bally et al. 1996). NH 3 (1,1) and (2,2) observations with the JVLA (Piñeda et al. 2015) additionally revealed the presence of filaments within the quiescent dense core. These filaments enclose three high-density bound condensations which, combined with IRS 1, might form a bound quadruple multiple star system (Piñeda et al. 2015). The WISE and 2MASS colors of IRS 1 suggests all consistence a Class I object.
Source No. 2 in (Table 3) is IRS 4 (IRAS 03446+3254), to the northeast of B5 and is the most evolved known YSO in B5 (Goldsmith et al. 1986;Langer et al. 1989;Yu et al. 1999). Molecular line maps show a large cavity having a diameter of 6 (Goldsmith et al. 1986;Langer et al. 1989;Arce et al. 2011), likely tracing a much older outflow. This target has a WISE Class II colors and a 2MASS colors consistent with being a mildly reddened classical TTauri star.
Source No. 3 previously not identified in the literature. We have classified it as a possible Class II, or a reddened dwarf.
Source No. 4, SSTc2d J034656.7+325248 was identified by Dunham et al. (2008) as a low-luminosity Class I protostar with 0.015 L based on 3.6-70 µm Spitzer data. This target is a WISE Class I, and is very close to the 2MASS classical TTauri loci.
Both Source No. 5 and 6 were identified as Class II YSOs by Dunham et al. (2015); Young et al. (2015); Evans et al. (2009) based on 3.6-24 µm Spitzer data, with the extinction corrected luminosity of 0.039 L (source no. 5) and 0.047 L (source no. 6). In Figure 10(a) both sources appear close to each other, and in 2MASS both the target appear together at the edge of the classical TTauri loci.
Source No. 7 is a known infrared source. The source does not have a 2MASS counterpart with the WISE colors suggesting a reddened Class I YSO, though Hsieh & Lai (2013) based on SPITZER c2d data have classified it as a probable galaxy contaminant. Source No. 8 is IRS 3 (IRAS 03439 + 3233) located towards the south-west of IRS 1, and drives small-scale Herbig-Haro objects, HH 367A and HH 367B, with HH 844 extending to the south (Walawender et al. 2005). This target is identified as a Class I object judging by both WISE and 2MASS colors.
Source No. 9 is classified marginally as a WISE Class II source, but in 2MASS the target is reddened and lies in the dwarf loci. Source No. 10 is also a marginal WISE Class II source. It does not have a 2MASS counterpart, and if reddening is considered, it could still be a Class II.
Source No. 11 is identified as Class II object and has a counterpart in our CFHT images. This target was followed up spectroscopically as a Q candidate brown dwarf in B5. In the 2MASS color-color plot this target lies near the dwarf loci. Source No. 12 is classified as Class II object based on WISE colors, but in 2MASS the target lies in the main sequence loci.
Source No. 13 is known as 2MASS J03472722+3230010. It is identified by Yao et al. (2018) as a disk-bearing source in IC 348. Considering its sky position, we associate it with B5 instead, and classify it as a Class II object.
Source No. 14 is classified as a WISE Class II object. Source No. 15 appears to be more reddened than source No. 14. In 2MASS both the targets appear in the reddened dwarf loci. Source No. 16 is a WISE Class I object, but does not have a 2MASS counterpart.
Note that of the four IRAS sources originally reported by Beichman et al. (1984), IRS 2 (IRAS 03449 + 3240) is colder (color temperature ∼ 25 K) but much less luminous (1.3 L ) than IRS 1. It was supposed to be either an internally powered prestellar core or an externally heated clump (Beichman et al. 1984). This source is not included in our YSO list because it is highly reddened (W 2 − W 3)=4.8, and therefore not categorized as any YSO class.

BULK MOTION OF PERSEUS SUBCLUSTERS
In addition to the study of B5 and IC 348 detailed above, we consider with Gaia EDR3 data of three other star-forming regions, namely, continuing westwards, Barnard 1, NGC 1333, andL 1448 (Barnard 203), together spanning across the Perseus molecular cloud. As in the analysis of IC 348, the kinematic grouping of each region is utilized to find the average proper-motion and parallax. For each of the regions we analyzed the Gaia EDR3 data in a ∼ 30 Gaia EDR3 field (see Figure 1). This angular size of the field was not meant to be optimal, but considered sufficiently large so as to cover the entire region to recognize a reliable group of stars in the proper-motion distribution. In B5, no such dis-tinct kinematic grouping is obvious, so a sample of young stars were utilized, the membership sample is small and within a narrow range of parallax (cf. Figure 12). Each of the remaining four regions exhibits a separate propermotion grouping for which the average proper-motion and parallax are computed. In every case a secondary peak exists that mimics the shape of the field distribution. The results of the Gaia EDR3 data for Barnard 1, NGC 1333, and L 1448 are presented in Figure 13. The IC 348 cluster experiences relatively low extinction, but is surrounded by heavy filaments, delineated by the paucity of Gaia EDR3 stars, in the south where ongoing star formation is taking place (cf., Figure 11(c)). The other rich cluster NGC 1333 in contrast coincides with the dense parts of the cloud, and has a shape elongated in NE-SW. L 1448 on the other hand seems to be offset to the north from the obscured patches. Barnard 1 appears marginally within our default 30 field, with the proper-motion and parallax "candidate members" scattering throughout the field, with no spatial concentration. Gaia star counts reveal the same NW-SW dark filament direction as detected by Walawender et al. (2005).
Ortiz- León et al. (2018) reported detailed VLBA and Gaia DR2 astrometry for IC 348 and NGC 1333, and with mean radial velocities, derived the 3D motion of the two clusters. For IC 348, our estimates of the average parallax of = 3.14±0.1 mas, and of the proper-motion of 4.4 ± 0.8, −6.3 ± 0.7 mas yr −1 agree within uncertainties with their Gaia parallax of Gaia = 3.09 mas, VLBA parallax of VLBA = 3.12 mas, and proper-motion of 4.35, −6.76 mas yr −1 . For NGC 1333, our values are also consistent with those reported by Ortiz-León et al. (2018) based on Gaia DR2 measurements.
The overall motion and orientation of the Perseus cloud complex probed by the five selected regions are summarized in Table 5 and depicted in Figure 14. In our analysis we compared the parallax measurement of each cloud, rather than the distance itself even though at this close distance the bias introduced in the reciprocal function in estimate of the distance (Bailer-Jones et al. 2021) is expected to be minimal. Our results support the earlier notion that the western complex is closer than the eastern part (Schlafly et al. 2014;Ortiz-León et al. 2018), and with a systematic trend in both propermotion and parallax extending further to include B5, the easternmost edge of the complex. While the near side is at some 300-320 pc (Pezzuto et al. 2021  For B5, Langer et al. (1989) concluded with the optically thin 13 CO tracer to derive some 1000 M of gas and dust, comparable to the virial mass, with a relative small fraction (∼ 200 M ) in the core and fragments. Our YSO census within the 30 field using 2MASS and WISE should be reasonably complete down to the magnitude limits. Our W band image though limited in spatial coverage led to the encouraging discovery of one brown dwarf. A survey more comprehensive than we reported here for the entire B5 cloud is desirable to further add to the substellar sample. In any case, given the few known YSOs, of which many are Class I objects, B5 appears to be in infancy in star formation and low in formation efficiency. The cloud subtends ∼ 1 • in the sky (Bensch 2006) which, adopting a distance of 400 pc, corresponds to a 7 pc linear dimension. B5 is certainly connected with the complex, witnessed in the continuation of the distribution of CO (see Figure 1) or the Herschel far-infrared data (their Fig. 4 Ortiz-León et al. 2018). If so, the fact that B5 stretches a depth (100 pc) more than the length scale projected on the sky plane suggests a bending morphology, alongside or on the backside of Per OB2 bubble, of this part of the complex. Massive stars upon birth interact and impact the neighboring environments. They may disrupt a nearby cloud to hamper any star formation activity. At a distance, however, these luminous stars via their winds and radiation could instead play a constructive role in compressing a cloud, thereby prompting the formation of the next generation of stars (Lee et al. 2005;Chen et al. 2007;. A supernova explosion has an even longer-range effect and produces a cavity that plows into an ever denser expanding shell of gas and dust, within which gravitational instability then leads to formation of giant molecular clouds that fragment hierarchically to form stellar groups (McCray & Kafatos 1987). Such a "collect-and-collapse' process can propagate on large (> 100 pc) scales, and indeed embedded star clusters are detected at the peripheral shells/rings of some H II regions (Zavagno et al. 2006). Differing timing of the explosive or photoionization shock fronts encountering with the surrounding clouds, plus possibly multiple supernova events in an OB association, results in an age spread in the YSOs thus induced to form. It has been suggested that Perseus OB2 (Per OB2) has such an influence in triggering the star formation in the Perseus cloud complex. Per OB2, located at a distance of ∼ 300 pc, is one of the major OB associations in the solar vicinity (de Zeeuw et al. 1999). Supernova explosion in Per OB2 drives an expanding H I supershell with a diameter of ∼ 20 • into the surrounding interstellar medium (Sancisi et al. 1974;Heiles 1984;Hartmann & Burton 1997). The eastern end of the Perseus cloud is close to the centroid of the supershell and to the OB association, exposing the part of the cloud now the cluster IC 348 resides as the first contact some 6 Myr ago in the sequence of triggered star formation (de Zeeuw et al. 1999;Ridge et al. 2006a;Bally et al. 2008).
Comparatively, the cluster NGC 1333 together with the associated reflection nebula and dark cloud L 1450 (Barnard 205) is the most rigorous star-forming region in the Perseus complex, manifest amply with embedded smm cores, protostellar jets/outflows, and shock-excited HH objects. With an estimated age of ∼ 1 Myr, the total stellar mass of ∼ 100 M signifies a star formation rate of 10 −4 M yr −1 . Except for the cluster IC 348 representing the earlier epoch of starbirth, the current episode of star formation appears to pervade throughout the complex including the regions we present in this work.

CONCLUSION
We present results from the W -band survey to search for brown dwarfs in IC 348 and in B5, and broad-band infrared colors to find young stars in B5. Our main results are: 1. W -band imaging, devised to detect the water absorption feature commonly seen in substellar objects, continues to demonstrate its effectiveness, providing a high positive rate of 90% for follow-up confirmation spectroscopy, to filter out reddened background sources. This work applied this tech-nique to two clouds at the eastern edge of the Perseus star-forming complex.
2. We found three previously unknown substellar objects in IC 348, enhancing the substellar sample in addition to the relatively well known stellar membership in the cluster.
3. Barnard 5 appears to be isolated with low level of star-forming activity. Our W -band images covering part of the cloud led to the discovery of the first brown dwarf in this region. Using WISE and 2MASS data we identified 16 young stellar objects, of which one new Class I and seven Class II objects were previously unknown. Barnard 5 should be at the initial stage of star birth, not necessarily as influenced by the neighboring Per OB2 as is the case for IC 348.
4. Using the Gaia EDR3 data of five selected starforming regions in the complex, we derived the distances of L 1448, NGC 1333, Barnard 1, and IC 348, progressively more distant from southwest to northeast, ranging 300-320 pc. The Barnard 5 cloud, however, is found to be considerably farther at ∼ 426 pc.