A fraction of the heavily reddened quasars require a reddening curve which is even steeper than that of the Small Magellanic Cloud .
In this paper , we thoroughly characterize the anomalously steep reddening law in quasars , via an exceptional example observed in IRAS 14026 + 4341 .
By comparing the observed spectrum to the quasar composite spectrum , we derive a reddening curve in the rest-frame wavelength range of 1200 Å–10000 Å .
It is featured with a steep rise at wavelengths shorter than 3000 Å , but no significant reddening at longer wavelengths .
The absence of dust reddening in optical continuum is confirmed by the normal broad-line Balmer decrement ( the H \alpha /H \beta ratio ) in IRAS 14026 + 4341 .
The anomalous reddening curve can be satisfactorily reproduced by a dust model containing silicate grains in a power-law size distribution , dn ( a ) / da \propto a ^ { -1.4 } , truncated at a maximum size a _ { max } = 70 ~ { } { nm } .
The unusual size distribution may be caused by the destruction of large “ stardust ” grains by quasar activities or a different dust formation mechanism ( i.e. , the in situ formation of dust grains in quasar outflows ) .
It is also possible that the analogies of the dust grains observed toward the Galactic center is responsible for the steep reddening curve .
In addition , we find that IRAS 14026 + 4341 is a weak emission-line quasar ( i.e. , PHL 1811 analogies ) with heavy dust reddening and blueshifted broad absorption lines .