SBS 0335–052 E and W: Implications of new broad-band and Hα photometry

We present the results of deep multicolour CCD imaging with the SAO RAS 6 m telescope of the pair of extremely metal-deficient gas-rich dwarf galaxies SBS 0335–052 E and W. The total magnitudes in $U,B,V,R$ and  I bands and the integrated fluxes of H α  emission are measured for both galaxies, and their integrated colours are derived. The analysis of their surface brightness (SB) distributions is performed with the use of the azimuthally-averaged SB profiles. The latter were modeled by the central Gaussian component and the underlying exponential “disk”, mainly contributing in the outermost, very low SB regions. The colours of these LSB components are used to estimate the age of the oldest visible stellar population. For the interpretation of the observed LSB colours their contamination by the nebular emission of ionized gas is accounted for by the use of the distribution of H α  flux. We compare the derived “gas-free” colours with the colours predicted by the evolution synthesis models from the PEGASE.2 package, considering three SF histories: a) instantaneous starburst; b) continuous star formation with constant SFR; and c) continuous exponentially fading SF (e-fold time of 3 Gyr). We conclude that the “gas-free” colours of the LSB component of the Eastern galaxy can be best consistent with the instantaneous starburst population (ages of $\la$100 Myr). Models with continuous SF give less consistent results, but can be considered as acceptable. For such scenarios, the “gas-free” colours require ages of $\la$400 Myr. For the Western galaxy, the situation is in general similar. But the colour $(V-R)$ appears to be quite red and implies a significantly older component. We briefly discuss the possible evolution sequence between SBS 0335–052, HI 1225+01 and other extremely metal-deficient galaxies based on the merger scenario.

[1]  C. Foltz,et al.  HS 0837+4717 - a metal-deficient blue compact galaxy with large nitrogen excess , 2004, astro-ph/0404171.

[2]  Abundance patterns in the low-metallicity emission-line galaxies from the Early Data Release of the Sloan Digital Sky Survey , 2003, astro-ph/0311564.

[3]  The Nature and Origin of the Nonvoid Lyα Cloud Population , 2003, astro-ph/0308390.

[4]  A. Kniazev,et al.  Starburst in HS 0822+3542 induced by the very blue LSB dwarf SAO 0822+3545 , 2003, astro-ph/0307556.

[5]  H. Hagen,et al.  The Hamburg/SAO Survey for low metallicity blue compact H II galaxies (HSS–LM) - I. The first list of 46 strong-lined galaxies , 2002, astro-ph/0209499.

[6]  The blue compact dwarf galaxy I Zw 18: A comparative study of its low-surface-brightness component , 2002, astro-ph/0207314.

[7]  N. Bergvall,et al.  Massive (?) starburst hosts of blue compact galaxies (BCGs) - Optical/near-IR observations of 4 BCGs and their companions , 2002, astro-ph/0205423.

[8]  C. Manning The Search for Intergalactic Hydrogen Clouds in Voids , 2002, astro-ph/0203195.

[9]  Metal Abundances of KISS Galaxies. I. Coarse Metal Abundances and the Metallicity-Luminosity Relation , 2002, astro-ph/0202301.

[10]  Kyiv,et al.  Deep spectroscopy of the low-metallicity blue compact dwarf galaxy SBS 0335-052 , 2001, astro-ph/0109254.

[11]  Kyiv,et al.  The evolutionary status of the low-metallicity blue compact dwarf galaxy SBS 0940+544. , 2001, astro-ph/0109256.

[12]  Usa,et al.  The deeply embedded starburst in SBS 0335-052 , 2001, astro-ph/0108012.

[13]  V. Lipovetsky,et al.  Environment status of blue compact galaxies and trigger of star formation , 2001 .

[14]  P. Weilbacher,et al.  On star formation rates in dwarf galaxies , 2001, astro-ph/0105282.

[15]  G. Östlin,et al.  Are there any Young Galaxies in our Local Universe? , 2001 .

[16]  V. Lipovetsky,et al.  VLA H I Line Observations of the Extremely Metal-Poor Blue Compact Dwarf Galaxy SBS 0335−052 , 2000, astro-ph/0011291.

[17]  P. Papaderos,et al.  An Imaging and Spectroscopic Study of the Very Metal-deficient Blue Compact Dwarf Galaxy Tol 1214−277 , 2000, astro-ph/0011227.

[18]  V. Springel Modelling star formation and feedback in simulations of interacting galaxies , 2000 .

[19]  A. Kniazev,et al.  Spectroscopy of candidate metal-deficient galaxies with the 6-m telescope , 2000 .

[20]  Tucson,et al.  Helium Abundance in the Most Metal-deficient Blue Compact Galaxies: I Zw 18 and SBS 0335–052 , 1999, astro-ph/9907228.

[21]  U. Hopp,et al.  SBSG 0335–052W: An Extremely Low Metallicity Dwarf Galaxy , 1999 .

[22]  Denis Foo Kune,et al.  Starburst99: Synthesis Models for Galaxies with Active Star Formation , 1999, astro-ph/9902334.

[23]  Heavy-Element Abundances in Blue Compact Galaxies , 1998, astro-ph/9811387.

[24]  M. Bureau,et al.  FCC 35 and Its H I Companion: Multiwavelength Observations and Interpretation , 1998, astro-ph/9803286.

[25]  M. Haynes,et al.  The Complex Kinematics of the Neutral Hydrogen Associated with I Zw 18 , 1997, astro-ph/9712070.

[26]  William D. Vacca,et al.  New Models for Wolf-Rayet and O Star Populations in Young Starbursts , 1997, astro-ph/9711140.

[27]  France.,et al.  A standard stellar library for evolutionary synthesis - II. The M dwarf extension , 1997, astro-ph/9710350.

[28]  T. Thuan,et al.  Nearby Young Dwarf Galaxies: Primordial Gas and Lyα Emission , 1997 .

[29]  D. Hunter STAR FORMATION IN IRREGULAR GALAXIES: A REVIEW OF SEVERAL KEY QUESTIONS , 1997 .

[30]  V. Lipovetsky,et al.  Detection of a second optical component in the H I cloud of the young dwarf galaxy SBS 0335-052 : New observations with the 6-m telescope , 1997 .

[31]  Frederic H. Chaffee,et al.  SBS 0335–052, A Probable Nearby Young Dwarf Galaxy: Evidence Pro and Con , 1997 .

[32]  Strasbourg,et al.  A standard stellar library for evolutionary synthesis: I. calibration of theoretical spectra , 1997, astro-ph/9701019.

[33]  V. A. Lipovetsky,et al.  Hubble Space Telescope Observations of the Blue Compact Dwarf SBS 0335–052: A Probable Young Galaxy , 1996 .

[34]  L. Girardi,et al.  Evolutionary sequences of stellar models with new radiative opacities. VI. $Z=0.0001$ , 1996 .

[35]  Ralph C. Bohlin,et al.  Spectrophotometric Standards From the Far-UV to the Near-IR on the White Dwarf Flux Scale , 1996 .

[36]  L. Hernquist,et al.  Gasdynamics and starbursts in major mergers , 1995, astro-ph/9512099.

[37]  R. Giovanelli,et al.  VLA Observations of HI 1225+01 , 1995 .

[38]  R. Kennicutt,et al.  Past and Future Star Formation in Disk Galaxies , 1994 .

[39]  Arlo U. Landolt,et al.  UBVRI Photometric Standard Stars in the Magnitude Range 11 , 1992 .

[40]  R. Giovanelli,et al.  The Optical Counterpart to the Large H I Cloud in Virgo , 1991 .

[41]  L. Hernquist,et al.  Fueling Starburst Galaxies with Gas-rich Mergers , 1991 .

[42]  J. A. Stepanian,et al.  Unusually low heavy-element abundance found in the blue compact dwarf galaxy SBS0335–052 , 1990, Nature.

[43]  P. Henning,et al.  A small spiral galaxy discovered at 21 centimeters in a cosmic void , 1989 .

[44]  N. Grevesse,et al.  Abundances of the elements: Meteoritic and solar , 1989 .

[45]  D. Hunter,et al.  STELLAR POPULATIONS AND STAR FORMATION IN IRREGULAR GALAXIES. , 1986 .

[46]  Lawrence H. Aller,et al.  Physics of thermal gaseous nebulae , 1984 .

[47]  A. Whitford The law of interstellar reddening. , 1958 .

[48]  E. Salpeter The Luminosity function and stellar evolution , 1955 .