SPECTROSCOPIC OBSERVATIONS OF
BYURAKAN-IRAS GALAXIES
Areg M. MICKAELIAN
Byurakan Astrophysical Observatory (BAO), Armenia
E-mail: [email protected]
ABSTRACT
A program of optical identifications of all IRAS sources in a large
area (|b|>15° and δ>+61°) on the basis of the First Byurakan
Survey (FBS) low-dispersion spectra is aimed at revealing all FIR
flux limited (0.6 Jy at 60µ, and 1.0 Jy at 100µ, i. e. the IRAS PSC
completeness limit) objects and study its contents. 1577 previously
unidentified IRAS point sources have been optically identified in an
area with 1487 deg2, of which 1178 are galaxies, and 399 are stars.
The identifications program brought to 2 samples of objects: BIS
(Byurakan-IRAS Stars), and BIG (Byurakan-IRAS Galaxies). A
redshift survey for BIG objects have been undertaken with 3
telescopes (Byurakan 2.6m, Russian SAO 6m, and HauteProvence 1.93m): 229 galaxies have been observed so far, and
their redshifts and activity types are available. The BIG objects
contain Seyferts, LINERs, composite spectrum AGNs, highluminosity IR galaxies, groups of galaxies, interacting and merging
galaxies, as well as obscured IRAS galaxies. The redshifts are in
the range 0.008-0.173, and the obtained FIR is in the range
3×109<Lfir/L<7.5×1012. Some of the interesting BIG objects have
been studied in details with the 2D spectroscopy.
“The life of galaxies”, JENAM-2004, 13-17 September 2004, Granada, Spain
The Byurakan-IRAS Galaxy (BIG) sample
A program of optical identifications of all IRAS PSC (IRAS 1988) sources at high galactic
latitudes has been conducted in the Byurakan Observatory since 1995 (Mickaelian 1995).
The First Byurakan Survey (FBS, Markarian et al. 1989) is the basis for this work. It is the
largest existing spectroscopic survey and gives possibility to estimate the nature of objects
by their spectra (color, emission and/or absorption lines, and SED). The area of the FBS
with +61°<δ<+90° at galactic latitudes |b|>15° has been taken with a total surface of 1487
deg2.
The identifications have been made on the basis of the First and Second Digital Sky
Surveys (DSS1, McGlynn et al. 1994; and DSS2, Lasker et al. 1996) images, the First
Byurakan Survey (FBS) low-dispersion spectra, and the IRAS infrared fluxes at 12µ, 25µ,
60µ and 100µ wavelengths (IRAS 1988; Moshir et al. 1990). The IRAS PSC completeness
limits at 60µ (0.6 Jy) and 100µ (1.0 Jy) are taken for making identifications thus obtaining
an IR flux limited sample (Mickaelian & Sargsyan 2004). The MAPS (Cabanela et al.
2003) and USNO-B1.0 (Monet et al. 2003) data have been used to get homogeneous
magnitudes for the identified objects. The IRAS FSC has been also checked for
identifications and all available data have been used (accurate positions and fluxes), as
well as radio and X-ray cross-correlations have given a number of coincidences with
NVSS (Condon et al. 1998), FIRST (White et al. 1999), ROSAT (Voges et al. 1999; 2000)
and other sources. 1577 sources have been optically identified, 1178 sources
corresponding to galaxies.
The BIG sample (Byurakan-IRAS Galaxies) was constructed of 1178 newly identified
galaxies and 789 other IRAS galaxies in the same area, known before, altogether 1967
galaxies. The galaxies have various appearance, structure and nature:
• compact galaxies,
• interacting pairs and groups (with tails and bridges between the objects),
• candidate “mergers”,
• radio and X-ray sources, etc.
Study of the sample will give a better understanding of star-formation, nuclear activity,
interactions and connections between these phenomena. 350 newly identified galaxies
are bright enough (B<18m) to undertake a quick redshift survey with the available
telescopes.
Studies of the BIG objects
The studies of the BIG objects include:
• spectroscopic follow-up for the brighter (<18m) objects (aimed at measuring their
redshifts and classification);
• discovery and study of new AGN;
• discovery and study of new ULIGs;
• deep imagery of the most interesting objects and the empty fields (search for faint
counterparts – obscured galaxies);
• 2D spectroscopy of interacting/merging systems;
• search for obscured IRAS galaxies (SIRTF/SST);
• study of starburst/AGN/interaction phenomena and their interrelationship.
IRAS 11067+7024
IRAS 17053+7402
IRAS 06584+6716
IRAS 16007+8137
IRAS 17046+6255
IRAS 16356+7225
Examples of interacting/merging pairs from the BIG sample
Direct image of IRAS 12120+6838 obtained with the BAO 2.6m telescope. 3 components
(on the left) are in tight interaction. The central component has a composite structure with
several concentrations. The galaxy on the right is also a member of this group.
Spectroscopic study of the bright BIG objects
Medium-dispersion spectral observations have been carried out for the BIG
objects during 1997-2002 and are being continued using the Special
Astrophysical Observatory (Russia) 6m, Observatoire de Haute-Provence
(France) 1.93m, and the Byurakan Astrophysical Observatory (Armenia)
2.6m telescopes (Mickaelian et al. 1998; 2003; Balayan et al 2001;
Mickaelian 2004). These observations are aimed at the investigation of space
distribution of IRAS galaxies and their IR luminosity function, discovery and
selection of AGNs, high luminosity IR galaxies, composite spectrum objects,
and their study in more details.
Statistics of observations of the BIG objects in 1997-2002
Telescope
BAO 2.6m
Equipment
ByuFOSC
Receivers
Dates
IRAS
BIG
sources objects
45
56
Sp.
Apr9875
Dec99
SCORPIO L 2063×2058 Feb02
9
16
17
SAO 6m
UAGS
Feb9748
64
84
K 585×530
Feb99
TK 1024
Mar99
MPFS
TK 1024
Sep9839
43
96
Jun00
OHP 1.93m CARELEC TK 1024
Oct97
64
69
74
EEV 2048
Jan99
All
1997181*
229*
346
2002
* Some objects have been observed several times with different telescopes
TM1060×514
Different spectral ranges have been observed with different equipment, from
3600 Å to 8000 Å. The dispersions are 1.8-5.8 Å/pix and spectral resolution
of 5-14 Å have been obtained. The S/N ratios vary in the range from 1:5 to
1:50, except of a few spectra. Study of the objects with different telescopes
and observational methods (e.g. MPFS is a multi-pupil spectrograph) is more
efficient both for quick fulfillment of the program and better quality of
classifications. The most interesting cases of AGN containing interacting
pairs are being studied by means of the 2D spectroscopy with MPFS.
The Redshift Survey of the BIG Objects:
Observing parameters
BAO 2.6m telescope
There are two spectral cameras: ByuFOSC-2 (Byurakan Faint Object
Spectral Camera) used with the 1060x1028, 19x19 mum Thomson CCD, and
the focal reducer SCORPIO used with the 2063x2058, 16x16 mum Loral
CCD. Two grisms available are sensitive in "green" and "red". 4
configurations have been used: 1) ByuFOSC-2 with the "green" grism:
dispersion 2.7 Å/pix, sp. resolution 8 Å, sp. range 4200-6900 Å; 2)
ByuFOSC-2 with the "red" grism: dispersion 2.1 Å/pix, sp. resolution 6 Å, sp.
range 5400-7600 Å; 3) SCORPIO with the "green" grism: dispersion
1.5 Å/pix, sp. resolution 5 Å, sp. range 3950-7200 Å; 4) SCORPIO with the
"red" grism: dispersion 1.3 Å/pix, sp. resolution 4 Å, sp. range 5150-7950 Å.
OHP 1.93m telescope
Spectrograph CARELEC (Lemaitre et al. 1989). Three configurations have
been used: 1) CCD TK512CB 512×512 with pixel size 27×27 mum, 150/mm
grating with dispersion 263 Å/mm (7.1 Å/pix), spectral range λ3810-7365Å
and spectral resolution 14.3 Å FWHM; 2) CCD TK512CB 512×512, 1200/mm
grating with dispersion 33 Å/mm (0.89 A/pix), spectral range λ6509-6965Å
and spectral resolution 1.8 Å FWHM; 3) CCD EEV42-20 2048×1024 with
pixel size 13.5×13.5 mum, 300/mm grating with dispersion 133 Å/mm (1.8
Å/pix), spectral range λ4262-7910Å and spectral resolution 6.6 Å FWHM.
SAO 6m telescope
UAGS spectrograph, and the 2D spectrograph MPFS (Afanasiev et al. 1995).
The UAGS (a long-slit fast spectrograph mounted at the prime focus) has
been used with two CCDs: Tektronix 580x530 pix and 1024x1024 pix.
Depending on the grating angle we have recorded one of the two spectral
ranges with the first CCD: 4500-7800Å or 3800-7000Å with a spectral
resolution of ~16 Å; and with the second CCD, 3600-8000Å with a slightly
higher resolution of 14 Å. The MPFS is a spectrograph intended for 2D
spectrophotometry of the extended objects with medium spectral resolution.
A spectral range of 3600-9600Å has been obtained, the dispersion is 1.355/pix, realized by a set of gratings of 300-1200 mm-1, and the resolution,
FWHM ~2.5 pix over the entire field of view. The detector used is CCD TK
1024x1024, with 24x24 mum/pix. The recorded data make a cube of
16x18x1024 elements.
The Redshift Survey of the BIG Objects:
Reduction, analysis and classification
Observed emission lines: Hγ, HeII λ4686, Hβ, [OIII] λλ4959/5007, HeI λ5876,
[FeVII] λ6087, [OI] λλ6300/6363, Hα, [NII] λλ6548/6584 and [SII] λλ6717/6731;
Observed absorption lines: MgI λ5180 and NaI λ5890; Hβ and Hα.
Continuum: stellar component (host galaxy) around the observed nucleus, color of
the galaxies.
Analysis: identification of spectral lines, their positions and redshifts, Full Widths at
0 Intensity - FW0I, Full Widths at Half Maximum - FWHM, Equivalent Widths EW, line intensities and their ratios.
Classification by types of activity:
Diagnostic diagrams (Veilleux & Osterbrock 1987), emission line ratios:
[OIII] λ5007/Hβ and [NII] λ6584/Hα, and [OIII] λ5007/Hβ and [OI] λ6300/Hα.
Empiric separation into Sy2, LINER & HIIs (Veron-Cetty & Veron 2000).
• HII – (HII regions) galaxies with starburst regions, including those with
nuclear starburst (Nuclear Starburst) (Terlevich 1997);
• LINER - Low Ionization Nuclear Emission Region (Heckman 1980);
• Sy2 – Seyfert galaxies with narrow emission lines;
• Composite – composite spectrum, consisting of both active nucleus (Sy2 or
LINER) and nuclear starburst region (Véron, Gonçalves & Véron-Cetty 1997).
• AGN - objects, showing evidence of activity by the emission lines without an
exact determination of the type;
• Em – spectra with evidence of emission without a possibility of more accurate
determination of the type of object.
Infrared luminosities:
Infrared luminosities (8-1000 mum):
Lir/L=5.6×105R2(13.56f12+5.26f25+2.54f60+f100)
Far Infrared luminosities (40-500 mum):
Lfir/L=5.6×105R2(2.58f60+f100)
(R – distance of objects in Mpc, f12, f25, f60 and f100 - IRAS fluxes at 12, 25, 60 and
100 mum, respectively; Duc, Mirabel & Maza 1997).
The Redshift Survey of the BIG Objects:
Results of observations
Redshifts:
Radial velocities:
Distances:
Absolute magnitudes:
LIR/L:
LFIR/L:
0.01194 ÷ 0.17344,
3560 ÷ 47580 km/sec,
47 ÷ 634 Mpc,
-16.7m ÷ -24.0m,
7.19×109 ÷ 1.16×1012,
3.59×109 ÷ 8.66×1011.
Classification by types of activity:
Sy2
LINER
AGN (Sy
LINER)
omposite
HII
Normal
Em
Abs
?
Not yet classified:
10
8
7
17
71
13
5
2
3
93 (some 30 more AGN are expected)
16 physical pairs
Radio- and high-luminosity IR sources:
86 NVSS sources (Condon et al. 1998), including 33 out of 42 AGN.
ULIRGs : 3 (IRAS 07479+7832 = BIG d141a, etc.)
LIRGs:
42
Spectra of 6 new Sy2 galaxies found among the BIG objects.
Diagnostic diagrams for BIG objects constructed on the basis of emission
lines intensity ratios: a) [OIII] 5007 / Hβ and [NII] 6584 / Hα; b) [OIII] 5007 /
Hβ and [OI] 6300 / Hα.
Distribution of the studied BIG objects by z, MV, Lir and Lfir.
Subsamples of the BIG Objects
Morphology and obtained spectra allow separate different interesting subsamples
for further studies. They are important for understanding of certain processes
taking place in galaxies. Evidence of activity, starburst and/or interactions at the
same object allows study connections between these phenomena and understand
what triggers the intense starburst processes.
Here are the main subsamples of BIG objects attracting attention:
AGN. The nuclear activity in galaxies is not finally understood yet. Numerous
types of active galaxies, making an “AGN zoo” are not fitted well in the
unified scheme. Hence, discovery of more AGN helps to solve this problem.
IRAS galaxies contain a large fraction of AGN, and it grows up with the IR
luminosity (Veilleux 2002). Are all high-luminosity IR galaxies AGN at higher
redshifts? BIG objects provide a number of interesting AGN, too. Many of
them are radio (NVSS; Condon et al. 1998) and X-ray (ROSAT: Voges et al.
1999) sources as well.
Composite spectrum objects. As it was mentioned, a number of galaxies
show simultaneously features of two different types of objects: e.g. HII and
Sy2, or HII and LINER. Such objects are important for study of different
emission-line regions and their co-existence in the same galaxy (Véron et al
1997).
High-luminosity IR galaxies: LIGs, ULIGs and HLIGs (Sanders & Mirabel
1996; Clements et al. 1999). Fainter galaxies in our BIG sample should
appear to be such objects, as they have nearly the same IR fluxes as
brighter galaxies (0.4-1.5 Jy at 60 mum and 1-3 Jy at 100 mum), but are
much fainter in optical range and hence, much farther. 30 IRAS sources
seeming to be real extragalactic objects (not cirruses) have no optical
counterparts at the IR positions. There must be objects with optical
magnitudes beyond the DSS limit.
Interacting galaxies and mergers. Revealed by the DSS images, they are
subject for further detailed study by 2D spectroscopy (MPFS observations
have been made for a number of them already), which gives the velocity field
of such objects and understanding of their relative motions. Is always the
high IR radiation due to merging process? (Clements et al. 1996).
Distant groups. Cross-correlations of the IRAS sources with higher positional
accuracy radio catalogs (particularly, the NVSS; Condon et al. 1998) allowed
select the correct optical counterpart among the several candidate objects
(Mickaelian et al. 2001). 766 NVSS sources coincide with the IRAS sources
in the investigated region. By matching with the MAPS database (Cabanela
et al. 2003), most of them coincide with a certain optical object. However, in
a number of cases, the IR radiation comes from a group of galaxies as a
whole. Many of these groups are compact.
Future Plans
The main aim of the program is to make a systematic study of a complete
sample of ultraluminous interacting IRAS galaxies to understand the
interrelationship between AGN and starburst activity induced by galaxy
merging and follow the evolutionary processes in these objects. The optical
identification program has produced a new IRAS galaxy sample - BIG.
The following studies of these objects are planned:
• study of the sample contents. In particular, the availability of optical and
IR (at 4 bands) data for many galaxies will help to clarify the
classification principles as well (relation between ULIG and activity
types);
• detailed optical study (morphology: study of interactions, fine structure
of central regions; and spectroscopy: determination of redshifts and
activity classes) of the newly identified IRAS galaxies and groups of
galaxies;
• near-infrared (mainly for some brighter galaxies) and radio millimeter
(for galaxies and QSOs) observations of newly identified objects;
• overall statistical study of the area, including previously identified IRAS
sources: space distribution and density of IRAS galaxies in the field,
their luminosity function and their connection with AGNs will be
investigated. The study of the sample of all galaxies in the field,
including the previously known and newly identified ones, will give the
most complete picture of the nearby Universe;
• comparison with the existing samples of IRAS galaxies and their
statistical conclusions on space density, evolution, star-formation rate
and status of the IR galaxies.
Taking into account that this program gives a complete sample of IRAS
galaxies in a large area, we hope to obtain the real distribution pattern of
extragalactic IR sources in the Local Universe. Large amount of interesting
objects (active galaxies, interacting systems, QSOs, planetary nebulae,
variable stars, etc.) among the IRAS sources makes important investigations
in this field, as their study leads to understanding of evolutionary phenomena
and processes taking place both in stars and galaxies.
PUBLICATIONS ON BIG OBJECTS
Review papers
1. Mickaelian A.M., Ap 38, 349, 1995.
2. Mickaelian A.M., Hakopian S.A., Balayan S.K., Proc. IAU S194, ASP, 156, 1999.
3. Mickaelian A.M., Proc. IAU S204, ASP, 69, 2001.
4. Mickaelian A.M., Balayan S.K., Hakopian S.A., AATr 20, 315, 2002.
Lists of BIG Objects
1. Mickaelian A.M., Ap 40, 1, 1997.
2. Mickaelian A.M., Gigoyan K.S., Russeil D., Ap 40, 379, 1997.
3. Mickaelian A.M., Gigoyan K.S., Ap 41, 161, 1998.
4. Mickaelian A.M., Gigoyan K.S., Ap 41, 232, 1998.
5. Mickaelian A.M., Ap 43, 425, 2000.
6. Mickaelian A.M., Ap 44, 43, 2001.
7. Mickaelian A.M., Ap 44, 227, 2001.
8. Mickaelian A.M., Ap 45, 357, 2002.
9. Mickaelian A.M., Sargsyan L.A., Afz 47, 109, 2004.
10. Mickaelian A.M., Sargsyan L.A., Afz 47, 251, 2004.
Spectral observations
1. Mickaelian A.M., Hakopian S.A., Balayan S.K., Burenkov A.N., Astron. Letters,
24, 635, 1998.
2. Balayan S.K., Hakopian S.A., Mickaelian A.M., Burenkov A.N., Astron. Letters,
27, 284, 2001.
3. Mickaelian A.M., Hakopian S.A., Balayan S.K., Dodonov S.N., Afanasiev V.L.,
Burenkov A.N., Moiseev A.V., Spec. Astrophys. Observ. Bulletin, 2002.
4. Mickaelian A.M., Balayan S.K., Hakopian S.A., Proc. IAU C184: AGN Surveys,
ASP Conf. Ser. 284, 217, 2002.
5. Mickaelian A.M., Hovhannisyan L.R., Sargsyan L.A., Afz 46, 221, 2003.
6. Mickaelian A.M., Afz 47, 425, 2004.
Other studies
1. Mickaelian A.M., Véron-Cetty M.P., Véron P., Proc. IAU S205, ASP, 232, 2001.
2. Mickaelian A.M., Hakopian S.A., Balayan S.K., Proc. IAU C184: AGN Surveys,
ASP Conf. Ser. 284, 220, 2002.
3. Mickaelian A.M., Proc. JENAM-2002, Kluwer Acad. Pub., 285, 76, 2003.
OTHER REFERENCES
Afanasiev V.L., et al. 1995, at http://www.sao.ru/bta/bta6m.html\#instr
Cabanela J.E., Humphreys R.M., Aldering, G., et al. 2003, PASP, 115, 837.
Clements D.L., Sutherland W.J., McMahon R.G., Saunders W. 1996, MNRAS, 279, 477.
Clements D.L., Saunders W.J., McMahon R.G. 1999, Mon. Not. Roy. Astron. Soc., 302,
391.
Condon J.J., Cotton W.D., Greisen E.W., Yin Q.F., Perley R.A., Taylor G.B.,
Broderick J.J. 1998, Astron. J., 115, 1693.
Duc P.-A., Mirabel I.F., Maza J. 1997, Astron. Astrophys. Suppl. Ser., 124, 533.
Heckman T.M. 1980, Astron. Astrophys., 87, 142.
IRAS 1988, Joint IRAS Science Working Group. Infrared Astronomical Satellite Catalogs,
The Point Source Catalog, Version 2.0, NASA RP-1190.
Lasker B.M., Doggett J., McLean B., et al. 1996, The Second Generation Digitized Sky
Survey, ASP Conf. Ser. 101, 88.
Lemaitre G., Kohler D., Lacroix D., Meunier J.-P., Vin A. 1989, Astron. Astrophys., 228,
546.
Markarian B.E., Lipovetski V.A., Stepanian J.A., Erastova L.K., Shapovalova A.I. 1989,
Commun. Special Astrophys. Obs., 62, 5.
McGlynn T., White N.E., Scollick K. 1994, ASP Conf. Ser., 61, 34.
Monet D.G., Levine S.E., Casian T., et al. 2003, Astron. J., 125, 984.
Moshir M., Kopan G., Conrow T., et al. 1990, Infrared Astronomical Satellite Catalogs, The
Faint Source Catalog, Version 2.0, NASA.
Sanders D.B., Mirabel I.F. 1996, Luminous Infrared Galaxies, Ann. Rev. Astron.
Astrophys., 34, 749.
Terlevich R.J. 1997, Rev. Mex. Astron. Astrofis., 6, 1.
Veilleux S. 2002, ASP Conf. Ser. 284, 111.
Veilleux S., Osterbrock D.E. 1987, Astrophys. J., 63, 295.
Véron P., Gonçalves A.C., Véron-Cetty M.-P. 1997, Astron. Astrophys., 319, 52.
Véron-Cetty M.-P., Véron P. 2000, Astron. Astrophys. Rev., 10, 81.
Voges W., Aschenbach B., Boller Th., et al. 1999, Astron. Astrophys., 349, 389.
Voges W., Aschenbach B., Boller Th., et al. 2000, MPE, Garching, 2000.
White R.L., Becker R.H., Helfand D.J., Gregg M.D. 1998, Astrophys. J., 475, 479.