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A z=0.45 DLA With Only Weak Mg II Absorption? Therese Jones1, J. C. Charlton1, A. C. Mshar1, G. J. Ferland2, P. C. Stancil3 Penn State Univ., 2University of Kentucky, 3University of Georgia.

1

The HE0001-2340 z=0.4523 system  Wr(Mg II 2796) = 0.14 Å

 Weak Mg II absorber (Wr(2796) < 0.3 Å)

 Voigt profile fit gave three clouds, at -69 km/s, 0 km/s, and 47 km/s

 Multiple cloud weak Mg II absorber

 Detected Mg I, Mg II, Fe I, Fe II, Ca I, Ca II, and Mn II in Cloud 1, Mg II and Fe II in Cloud 2, and only Mg II in Cloud 3

 No hydrogen to constrain the metallicity of the system due to a Lyman limit system at z= 2.1853

 Fe I detection is extremely rare; only known detections in dense Milky Way clouds

 Used Cloudy (Ferland 2006) to model the system  Were able to fit Clouds 2 and 3 by varying the ionization parameter  Cloud 2 (two components: log N = 11.79 cm-2, b= 5.09 km/s; log N = 12.36 cm-2, b= 2.77 km/s) fit with Z=0.1 ZΘ, log U = -3.8  Cloud 3 (log N = 11.67 cm-2, b=14.53 km/s) fit with a wide range of metallicities and ionization parameters  Cloud 1 not fit by changing the ionization parameter or the metallicity; Fe I was never produced, and Fe II was underproduced

 Changing the abundance pattern is not reasonable

 N(Fe I/Fe II) not close to the observed ratio in any model

 Abundance of Fe would have to be increased by unphysical amounts to account for the Fe I

 Are the current Fe I and Mg I charge transfer rates correct?

 Cloudy adopts a small Mg I charge transfer rate and a large Fe I charge transfer rate at low temperatures

 Previously it was thought that both charge transfer rates were small at such a temperature regime

 Models with small charge transfer rates give a two-phase solution to Cloud 1, with a Mg II phase with log N = 14.01, b = 0.50 km/s, Z = 0.01 ZΘ, log U = -7.5, T= 86 K, and a Mg I phase with log N = 12.65, b = 0.20 km/s, Z= ZΘ, log U = -7.5, T= 136 K

 If both charge transfer rates are large, the system can be fit with one phase, with log N = 13.99, b = 0.20, Z= 0.1 ZΘ, log U = -8.5 , and T= 26 K

Conclusions  Ca I, Ca II, and Mn II generally only seen in DLAs, and high column density proposed by the models also seem to suggest a DLA

 System is extraordinarily unusual for its detection of Fe I

 Different charge transfer rates can explain the detected Fe I

 Also a possibility that the system is not in equilibrium

 A new class of system?