We present Giant Meterwave Radio Telescope ( GMRT ) observations of the H i 21 cm line and Very Large Array ( VLA ) observations of the OH 18 cm line from the Seyfert 2 galaxy Mrk 1 .
H i emission is detected from both Mrk 1 and its companion NGC 451 .
The H i emission morphology and the velocity field of Mrk 1 are disturbed .
We speculate that the nuclear activities of Mrk 1 are triggered by tidal interactions .
We estimate the H i masses of Mrk 1 and NGC 451 to be 8.0 ( \pm 0.6 ) \times 10 ^ { 8 } M _ { \odot } and 1.3 ( \pm 0.1 ) \times 10 ^ { 9 } M _ { \odot } respectively .
We have also detected the H i 21 cm line and the OH 18 cm line in absorption toward the nucleus of Mrk 1 at a blueshifted velocity with respect to its systemic velocity indicating an outflow of atomic and molecular gas .
Two OH lines , at 1665 and 1667 MHz , are detected .
Each of the profiles of the H i and OH absorption consists of two components that are separated by \sim 125 km s ^ { -1 } .
Gaussian fitting gave dispersions of \sim 44 km s ^ { -1 } for both the components of the H i absorption .
The profile of the OH absorption is qualitatively similar to that of the H i absorption .
Both components of the OH absorption are thermally excited .
The peak optical depths of the two components of the H i absorption are ( 7.3 \pm 0.4 ) \times 10 ^ { -2 } and ( 3.2 \pm 0.4 ) \times 10 ^ { -2 } .
The corresponding peak optical depths of the 1667 MHz OH absorption are ( 2.3 \pm 0.3 ) \times 10 ^ { -2 } and ( 1.1 \pm 0.3 ) \times 10 ^ { -2 } .
The higher velocity components of the H i and OH ( 1667 MHz ) absorption lines are blueshifted from the [ O iii ] \lambda 5007 , [ O i ] \lambda 6300 , and the systemic velocity by \sim 100 km s ^ { -1 } , but are consistent with the [ O ii ] \lambda 3727 velocity .
We explain these velocity discrepancies as due to shock ionization of a region which is pushed forward due to shocks in front of the radio nucleus thereby giving apparent blueshift to H i , OH , and [ O ii ] velocities .
The optical depth ratios \tau _ { \mathrm { { H \textsc { i } } } } / \tau _ { \mathrm { OH } } ^ { 1667 } of both the components of the H i and OH absorption are \sim 3 , indicating their origin in dense molecular clouds .
Using OH/A _ { \mathrm { v } } values for the Galactic molecular clouds , we obtain 9 < A _ { \mathrm { v } } < 90 toward the line of sight of Mrk 1 .