(1) Atlas and Catalog of Dark Clouds Based on the 2 Micron All Sky Survey

 

We release an atlas and catalog of dark clouds derived based on the 2 Micron All Sky Survey Point Source Catalog (2MASS PSC). Color excess maps of E(J-H) and E(H-KS) as well as extinction maps of AJ , AH, and AKs covering all of the sky have been produced at a grid of 1'. On the basis of the E(J-H) and AJ  maps, we have carried out a systematic survey for dark clouds all over the sky. In total, we identified 7614 dark clouds, and measured the coordinates, extents, and AV values for each of them. These cloud parameters are compiled into a new catalog of dark clouds, which was published in a special issue of the Publications of the Astronomical Society of Japan (PASJ) in 2011 January (Dobashi et al. 2011, PASJ, vol.63 SP1, pp.S1-S362). Electronic version of the paper can be found at http://pasj.asj.or.jp/v63/v63s1.html. Please look into the paper for detailed explanations of the data.

After releasing the extinction and color excess maps on our website in 2010, we found that the maps had some problem in the determination of the background. We later corrected this problem by utilizing the Besançn Galaxy Model (Robin et al. 2003, A&A, vol. 409, p. 523) with a great help of Dr. Douglas J. Marshall, for which our extinction and color excess maps have been improved very much. Details of the correction are fully described in a subsequent publication (Dobashi et al. 2013, PASJ, vol.65 No.2, article No. 31).

The atlas and catalog derived from the 2MASS PSC mainly trace relatively dense regions in dark clouds revealing a number of dense cloud cores leading to star formation, while those we derived previously from the optical database Digitized Sky Survey I (DSS, Dobashi et al. 2005, PASJ, vol.57, SP1, pp.S1-S386) are more suited to trace less dense regions and to reveal the global extents of dark clouds. The two datasets are complementary, and all together, they are useful to picture the structures of dark clouds in various density ranges.

 

(2) Data released on this website

 

The atlas and catalog of dark clouds based on the 2MASS PSC are released in FITS and text files on this website. We have drawn maps in the atlas at the 1’ and 15’ grid. Maps drawn at the 15’ grid have a constant angular resolution of 1 degree, while those drawn at the 1’ grid have a changing angular resolution from 1’ to 12’ depending on regions in the sky to achieve a constant noise level over a large region. For details, please see our original paper in PASJ.

As summarized in the following tables, we release the maps drawn at the 1’ grid in FITS format on this website together with some other related data such as the angular resolutions and noise levels. They can be found at http://darkclouds.u-gakugei.ac.jp/2MASS/all.html. List of the identified clouds is also released in a text file (ascii) which can be found at http://darkclouds.u-gakugei.ac.jp/2MASS/cloud_list.txt.

 

(3) Policy and Copyright

 

Copyright of the text and FITS data on this website entirely belongs to Tokyo Gakugei University. However, the data can be used by anyone for astronomical researches and education purposes.

(4) Additional Information and Request to Users

 

We request users of the data released on this website to refer to our paper "Dobashi et al. 2011, PASJ, Vol.63 SP1, pp.S1-S362" when they use the data for publications (papers or articles). This is important not only for us but also for users, because your referring to the paper would greatly encourage us to find a financial support to maintain and develop this website. We would very much appreciate your contribution.

We have done our best to guarantee the high quality of the data, but there might be some errors. If you should find an error, please let us know via e-mail (dobashi@u-gakugei.ac.jp), so that we can revise the data immediately.

(5) Contact Address

 

If you have a question, suggestion, or request about the data, please send an e-mail to me Kazuhito DOBASHI (dobashi@u-gakugei.ac.jp).

 

(6) Acknowledgement

 

This website is financially supported by Grant-in-Aid for Scientific Research (Nos. 178059, 188065, 198049, 208040, 218044, 228037, 248028, 258031, 15HP8026 and 16HP8023) of Japan Society for the Promotion of Science (JSPS).

 

Abstract of the paper

 

This paper presents an atlas and catalog of dark clouds derived based on the 2Micron All Sky Survey Point Source Catalog (2MASS PSC). Color excess maps of
E(J-H) and E(H-Ks) as well as extinction maps of AJ , AH, and AKs covering all of the sky have been produced at a grid of 1'. Maps drawn at a lower grid of 15' were also derived for various sets of the threshold magnitudes in the J, H, and Ks bands to estimate the background star colors and star densities needed to derive the color excess and extinction maps. The maps obtained in this work are presented on various scales in a series of figures that can be used as an atlas of dark clouds for general research purpose. On the basis of the E(J-H) and AJ maps drawn at the 1' grid, we have carried out a systematic survey for dark clouds all over the sky. In total, we identified 7614 dark clouds, and measured the coordinates, extents, and Av values for each of them. We also searched for their counterparts in the previously published catalog of dark clouds based on the optical photographic plates DSS (Dobashi et al. 2005, PASJ, vol.57, SP1, pp.S1-S386). These cloud parameters including the information of the counterparts are compiled into a new catalog of dark clouds.

The atlas and catalog organized in this paper mainly trace relatively dense regions in dark clouds revealing a number of dense cloud cores leading to star formation, while those presented by Dobashi et al. (2005) based on the optical database are more suited to trace less dense regions and to reveal the global extents of dark clouds. These two datasets are complementary, and all together, they are useful to picture the structures
of dark clouds in various density ranges.

File Summary

 

FileName	Records	Explanations
ReadMe_2MASS_Dobashi.txt		This file
cloud_list.txt	7614	Catalog of Dark Clouds (Table 8 of Dobashi et al. 2010)

 

FITS data on this website

 

No.	Data	Unit	Explanation
1	Core Map	mag	Extinction map of AV derived from E(J-H) and AJ map. Extended dust components are removed in this map, so that one can easily find dense regions in dark clouds (i.e., dense cores). See Section 7 of Dobashi (2011).
2	1 sigma noise	mag	1 sigma noise level map of the Core Map.
3	Core Number	-	Numbers (from 1 to 7614) for clouds identified in the Core Map. See Section 7 of Dobashi (2011).
4	Mask	-	A value 1 or 0 is given. 1 is for the region where we used the AJ map to compose the Core Map, and 0 is for the region where we used the E(J-H) map. See Figs. 30 and 31d of Dobashi (2011).
5	Radius	arcmin	Radius R to include a constant number of stars (N~21) to measure the color excess and extinction. 2R gives the common angular resolution of all of the color excess and extinction maps. See Fig.5 of Dobashi (2011).
6	AJ	mag	Extinction map of AJ. See Equations (9)-(13) of Dobashi (2011).
7	1 sigma noise of AJ	mag	1 sigma noise level of the AJ map. See Section 6.1 of Dobashi (2011).
8	Number of stars in the AJ map	-	Number of stars used to produce the AJ map.
9	J-band star density	arcmin^-2	Star density map used to produce the AJ map. See Fig.14a of Dobashi (2011).
10	AH	mag	Extinction map of AH. See Equations (9)-(13) of Dobashi (2011).
11	1 sigma noise of AH	mag	1 sigma noise level of the AH map. See Section 6.1 of Dobashi (2011).
12	Number of stars in the AH map	-	Number of stars used to produce the AH map.
13	H-band star density	arcmin^-2	Star density map used to produce the AH map. See Fig.14b of Dobashi (2011).
14	AK	mag	Extinction map of AK. See Equations (9)-(13) of Dobashi (2011).
15	1 sigma noise of AK	mag	1 sigma noise level of the AK map. See Section 6.1 of Dobashi (2011).
16	Number of stars in the AK map	-	Number of stars used to produce the AK map.
17	K-band star density	arcmin^-2	Star density map used to produce the AK map. See Fig.14c of Dobashi (2011).
18	E(J-H) at X-95%	mag	Color excess map of E(J-H) measured in the (X, 95) % range. See Equation (4) of Dobashi (2011).
19	1 sigma noise of E(J-H)	mag	1 sigma noise level of the E(J-H) map in the (X, 95) % range. See Section 6.1 of Dobashi (2011).
20	Number of stars used in the E(J-H)	-	Number of stars used to produce the E(J-H) map in the (X, 95) % range.
21	J-H at X-95%	mag	Star color of J-H used to produce the E(J-H) map in the (X, 95) % range. See Equation (2) of Dobashi (2011).
22	E(J-H) at X %	mag	Color excess map of E(J-H) measured at X %. See Equation (3) of Dobashi (2011).
23	1 sigma noise of E(J-H)	mag	1 sigma noise level of the E(J-H) map at X %. See Section 6.1 of Dobashi (2011).
24	J-H at X %	mag	Star color of J-H used to produce the E(J-H) map at X %. See Equation (1) of Dobashi (2011).
25	E(H-K) at X-95%	mag	Color excess map of E(H-K) measured in the (X, 95) % range. See Equation (4) of Dobashi (2011).
26	1 sigma noise of E(H-K)	mag	1 sigma noise level of the E(H-K) map in the (X, 95) % range. See Section 6.1 of Dobashi (2011).
27	Number of stars used in the E(H-K)	-	Number of stars used to produce the E(H-K) map in the (X, 95) % range.
28	H-K at X-95%	mag	Star color of H-K used to produce the E(H-K) map in the (X, 95) % range. See Equation (2) of Dobashi (2011).
29	E(H-K) at X %	mag	Color excess map of E(H-K) measured at X %. See Equation (3) of Dobashi (2011).
30	1 sigma noise of E(H-K)	mag	1 sigma noise level of the E(H-K) map at X %. See Section 6.1 of Dobashi (2011).
31	H-K at X %	mag	Star color of H-K used to produce the E(H-K) map at X %. See Equation (1) of Dobashi (2011).
Note. “X” in the above No. 18-31 changes from X=5 % to 90 % with a step of 5%.

 

 

Byte-by-byte Description of the file: cloud_list.txt

 

---

Byte

Format

Unit

Label

Explanations

---

2-5	I4	---	---	Sequential number for cloud name (from 1 to 7614).
7-9	I3	deg	GLONd	Galactic longitude (degrees) of the clouds.
12-13	I2	min	GLONm	Galactic longitude (minutes) of the clouds.
16	A1	---	GLAT-	Galactic latitude (sign) of the clouds.
20-21	I2	deg	GLATd	Galactic latitude (degrees) of the clouds.
24-25	I2	min	GLATm	Galactic latitude (minutes) of the clouds.
28-34	F7.2	arcmin^2		Surface Surface area of the clouds in square arcmin.
36-40	F5.2	mag	Av	Peak Av value of the clouds in the core map.
43-46	F4.2	mag	dAv	1 sigma noise level of the peak Av.
52-59	F8.2	mag arcmin^2	SAvds	Extinction integrated over the cloud surface.
69-72	F4.2	mag arcmin^2	dSAvds	1 sigma noise level of the extinction integrated over the cloud surface.
77	A1	---	Rank	Rank of reliability in detection (from A to C, see below).
79-85	A7	---	Flag	Flag (from 0 to 8, see below).
87-92	A7	---	TGU	Counterpart in the TGUH catalog, i.e., the number of clouds in Table 7 of Dobashi et al. (2005, PASJ, vol.57, SP1, S1-S386).

---

 

Note on Rank (A-C)

 

---

	A =Clouds having a counterpart in one or more other database, ensuring that the cloud is real. There are 7350 clouds classified Rank A.
	B =Clouds falling in the outskirts of the distribution of dense gas or dust found in other database, and their counterpart cannot be identified clearly. There are 210 clouds classified Rank B, and some of them might be fake.
	C =Clouds heavily affected by bright stars in the vicinity, and cloud parameters such as Av cannot be measured reliably. There are 54 clouds classified Rank C, and some of them might be fake.

---

 

Note on Flag (0-8)

 

---

	0 =Clouds originating from the E(J-H) map (i.e., the Exm map at X0=50%). There are 5255 clouds assigned this flag.
	1 =Clouds originating from the AJ map. There are 2359 clouds assigned this flag.
	2 =Distant clouds appearing as a hole in the E(J-H) map, but as a bump in the AJ map (see subsection 6.6 of Dobashi 2010). There are 747 clouds assigned this flag.
	3 =Clouds possibly contaminated by IR clusters appearing as a hole in the AJ map, but as a bump in the E(J-H) map (subsection 6.4). There are 543 clouds assigned this flag.
	4 =Clouds found in the vicinity of bright stars in the SAO catalog (=< 6 mag), which may affect our estimate of Av . There are 15 clouds assigned this flag.
	5 =Clouds found in the vicinity of bright stars in the 2MASS PSC (<=5 mag either in J, H, or Ks bands), which may affect our estimates of Av . There are 40 clouds assigned this flag.
	6 =Clouds found within the radii of globular clusters cataloged by Monella (1985), which may affect our estimates of Av . There is only 1 cloud assigned this flag.
	7 =Clouds found in the radii of open clusters cataloged by Dias et al. (2002), which may affect our estimates of Av . There are 48 clouds assigned this flag.
	8 =Clouds in M31 and M33 (subsection 6.7). There are 15 clouds assigned this flag.

---